The Miserable State of Opto-Mechanical Design in the World of Amateur Astronomy Gear

22.76 John Hayes #... · view views · 41 likes
A new affliction has recently washed over the world of astro-imaging—namely: sensor tilt. Everywhere I look, sensor tilt is either screwing up an imaging system or it’s being blamed for screwing up an imaging system. And that has led to fixes such as the Octopi camera interface adapter that allow fine adjustment to both sensor spacing and tilt. Faster optical systems and cameras with smaller pixels both work to tighten the requirements on camera tilt and position but to a large extent, the difficulty of aligning cameras has been exacerbated by the really poor mechanical design of many of the components that need to be stacked up in the image train. Poor design is an issue that has caused me to tear my hair out in frustration so many times that I thought I’d post a brief review of common problems along with a very short introduction to optomechanical design principles. My background in optics is primarily in interferometry and optical testing, but I’ve had a serious interest in optomechanics for as long as I can remember. To be clear, the field of optomechanics addresses the specific design challenges associated with optical systems. It involves understanding how to analyze and mount optical components to minimize strain and mechanical distortion, how to achieve and maintain precision alignment, how to select proper materials, how to tolerance mechanical requirements, and how to deal with thermal effects. Lying at the core of all of this, are the basic principles of precision positioning and from what I’ve observed, this is where nearly every (not quite all!) astro-equipment manufacturer falls apart. Let’s look at just a few examples of poor design that have driven me crazy. Our first example comes from Planewave Instruments. The photos below show the end views of the main dovetail/carriage adapter that they supplied with my 20” telescope back in early 2020. They've shipped a lot of these things and for the life of me, I can’t understand why anyone thinks that it’s acceptable. The mechanics are so faulty that the entire weight of the telescope is held between a couple of pinch points in the carriage and the strength of the connection fall onto the screws themselves. Furthermore, the screws bind so terribly as the dovetail begins to engage that it’s hard to tell when the screws are properly torqued. Grade: D- As an offer of good will, I suggested the simple design modification shown below to fix the design without having to start completely from scratch. In the end, Planewave declined to fix it so I returned it and replaced the carriage with one from Astro-Physics. The Astro-Physics carriage is beautifully designed and implemented. Designing a well implemented dovetail/carriage is not that hard and in spite of that fact, Planewave isn’t the only company that has had problems pulling it off. I’ve seen similar issues from Celestron with their orange extruded dovetails as well, but I’ve made the point so we’ll skip those photos. Next on the list: I’ve got a FLI filter wheel for my F/6.7 refractor and for no extra charge, they included a mechanical problem that is so difficult to fix that I had to replace the entire assembly with another brand. In order to try to minimize the thickness of the filter wheel, the FLI design uses only two setscrews located at 120 degrees to mount a dovetail on the camera side of the wheel. The diagram below shows what happens when the screws are tightened. The two sets screws do what they are supposed to do, which is to draw the dovetail down into the mounting hole, but since there is no opposing screw (or lip) on the other side, the camera gets tilted. No amount of shimming will fix this problem! They would have been better off using just a plain cylindrical surface instead of a dovetail. It’s difficult to solve this problem in a clean way without seriously re-machining some of the parts. Grade: F I replaced the FLI FW with a new one from Pegasus Astro. The Indigo filter wheel mounts 50 mm round filters, it is very inexpensive and at first blush, it looks like a very simple, if not, elegant design. It is very thin, it runs off of USB, and it allows bolting adapters directly to the filter wheel. Unfortunately, it doesn’t take long to uncover multiple problems with this design. First, they use arcing slotted holes to mount adapters and those holes open directly into the filter cavity, which will cover the filters with dust in no short order! What in the world were they thinking??? Fortunately, they designed bolt on covers to cover the holes and as fast as I could complain, they shipped them to me free of charge from Greece. The next problem rears its head when you mount the filters. The diagram below shows the problem. The screw and washer retainer system is workable but the way that it’s implemented is just sloppy! In my professional life, I’ve shipped optical equipment that I designed all over the world and the first rule is that any screw that isn’t locked, WILL come loose in shipping. Since I’m sending this FW to Chile, I have to address this issue in a serious way. The final problem with the Indigo FW involves the friction drive wheel on the edge of the filter wheel. It's the blue wheel in the photo above. Unfortunately, they fixed the position of the friction wheel. It’s adjustable for wear, but that’s only possible if you are there—as in when the FW is used in your backyard. That really doesn’t cut it when you are shipping equipment to a very remote location where service can be difficult and where you certainly don’t want to be opening the FW to expose the filters to dust. The drive wheel should have been pre-loaded against the edge of the filter carrier using a simple flexure spring. Additional cost: Very low. As it is, the mechanical design of this product is not very sophisticated. Grade: C-/D+. The good news is that they could clean up this design fairly easily…if they want to. Last on my list is an issue that probably affects a lot of QHY camera owners. When I switched filter wheels, I had to use the QHY supplied carriage designed to mate to the V-notch “dovetail” on the front of the camera. I was stunned to see just how poorly constrained this whole system is! First, the carriage is seriously over-sized to allow for centering the camera. Let me get something straight here: The only reason you might want to center the camera is if your mechanics are so screwed up in the first place that you can’t mount the carriage where it is supposed to go! More adjustments almost always makes for more misalignment! With this system, it becomes very hard to tell when your camera is precisely centered, but fortunately, centration is not very critical on most systems. Here’s a diagram of how the camera mounts. The much, much bigger problem is that QHY designed the V-notch spacing so that the centering screws engage it with the camera hanging in space—referenced to absolutely nothing! The centering screws are mounted in loose fit threaded holes and the tips of the screws aren’t coned or spherical. There is simply nothing that defines the angle of the camera! It might be close enough but more likely, the camera will be tilted a bit, no matter what you do. So, in the end you can’t tell when the camera is centered and you sure as heck can’t tell if it’s tilted either. Furthermore, the spacing from the front surface of the V-notch carriage to the sensor depends on how well the screw hole positions are controlled and on the unknown shape of the screw-tips. This is just a mess. The guys at QHY appear to be experts at electronics but in my opinion, their opto-mechanical skills are seriously flawed. No wonder so many folks are buying Ocupi adjusters! Grade for the QHY V-notch mount: F- Fortunately, there is an easy fix to better control the tilt of the camera shown in the diagram below. First, a conical tip can be ground onto the tip of the centering screws. Second, by carefully measuring the top gap between the V-tail adapter face and the V-tail carriage (using feeler gauges), a circular washer can be cut from plastic shim stock with a bit of extra thickness (maybe 0.010” to 0.015”) to allow the centering screws to contact the bottom edge of the V-notch to pull the V-notch adapter face tight against the shim washer. Astro-Physics uses a V-notch system on their field flatteners but they’ve implemented it correctly so that the retaining screws only engage one edge of the V-notch pulling the adapter and mount tightly together along a reference surface. The diagram below shows the fix. Alternatively, the holes for the screws could be repositioned using a mill and an index table, but that's a lot more work. I'll do it if I need to move the camera inward. The ultimate fix would be to just redesign that whole front V-notch part to be a straight dove-tail...as it should have been in the first place! Finally, I’ll give an honorable-mention to Celestron for their utterly poor mechanical design of the secondary mount on their Edge series of SCTs. That design is not well constrained in angle or position and that results in having to realign the secondary every time it is removed or after something as simple as a car trip. Years ago, I completely redesigned the secondary mount on my prototype C14 using kinematic principles and demonstrated on an interferometer that it could hold alignment to within about 5 fringes across the pupil even after pulling the secondary out and remounting it. (The factory version controlled tilt 20-40 times worse!). It had super easy to use, orthogonal tilt adjustment and using CNC, it could be made for only a few more dollars than the existing design. I offered the design to Celestron but it wasn’t worth it to them so they passed. Too bad. It worked incredibly well and the added cost would have been minimal. What’s the solution? I’ve tossed out a lot of examples of poor designs but I don’t want it to sound like all problem and no solution. So, let’s look at a few basic design principles that hopefully will begin to seep into the Astro-Equipment market. Kinematic Constraint A rigid body has six degrees of freedom, which includes 3 translational and 3 rotational axis. A degree of freedom can be controlled by connecting it to a rigid mechanical constraint. The principle of kinematic constraint is to control any unwanted motion (in position or angle) along a single degree of freedom with a single constraint. A kinematic constraint is geometrically defined and repeatable to a high degree of accuracy—often limited only by the mechanical stiffness of the constraint itself. A degree of freedom is over-constrained when more than a single constraint controls motion along that particular axis. Over constraint causes binding, distortion, and can lead to poor positional performance. In the worst case, it can also allow unwanted motion along that axis. More is not always better! Let’s look at some quick, very simple examples of kinematic constraint. 1) A perfect ball on a perfect flat surface constrains a single degree of freedom 2) A high precision ball bearing rolling in a precision ground V-groove constrains two translational degrees of freedom so that the ball can only roll along a single axis. 3) A single ball in point contact with three balls restrained within a circular ring constrains all three degrees of translational freedom. While we are at it, here are some common non-kinematic design choices. 1) Attaching one flat plate to another to constrain tilt. Any departure from flat in the way of high points (or from contamination such as dirt on the surface) makes the angle uncertain. There is no way to tell how the plates contact. Yes, you can lap them together and you can go to a lot of trouble to reduce errors but no matter how careful you are the repeatability and accuracy of controlling angle by mating two large area surfaces will be limited. Another form of this method is to butt two edges together. Again, this is not a kinematic solution. 2) Bolting one plate to another to control position. Bolt holes are oversized and bolt sizes vary. Bolting two plates together simply connects them with very little position control. 3) Controlling angle with two widely separated pins that fit into mating precision holes. This is an example of an over-constrained design. The pins and holes have to be co-aligned and the hole spacing has to perfectly match the pin spacing. Furthermore, a pin in a hole does not precisely control the position of the mating parts. This is what diamond pins are made for! Pseudo or Semi-Kinematic Design Psuedo Kinematic design uses the same geometry and concepts at a pure kinematic design but allows for very small over-constraint. For example, in order to control the tilt of a flat surface, you would ideally place it in contact with three non-linear rigid balls (for single point contact). However, space or cost constraints may make it difficult to implement a full kinematic design. In that case, you might simply machine the mounting base to include three very small raised rectangular pads for the mating surface to mount to. Since the raised pads do not provide a single point of contact, they over-constrain the solution. However, this kind of pseudo-kinematic approach can improve mechanical performance enormously over a totally non-kinematic solution. If you want to connect the two surfaces, placing a connecting screw through the raised pads minimizes the mechanical distortion of either plate. Another not so obvious example of a psuedo-kinematic constraint is a ball in a conical hole. The problem is that a ball intercepts a cone along a circle and you don’t have a way to generate a geometrically perfect conical hole. The true kinematic solution constrains the ball position using point contact with three touching balls below. When carefully applied, psuedo-kinematics can solve a LOT of the issues that I've listed here without adding significant to the cost of a product. Conclusion It is unfortunate that there appear to be so few companies in the astro-equipment world that are even aware of kinematic design. Worse, as I've mentioned, I've even tried to help a few of them with their design problems and I've been turned down. So, I get the impression that it's not a very high priority to get the mechanics right. That means that we customers are often left dealing with marginal designs--even from high end companies! In my experience, the one company that works very hard to produce excellent mechanics is Astro-Physics. Their designs are almost always spot on. I want to add that I haven't examined products from every company so I'm sure that there are others out there who are paying attention to the mechanics as well. Telescope and equipment alignment would be far, far easier and more precise if more components were properly designed and made! Starting with something that's a mess and then having to add another adjuster to compensate for all of the errors is fundamentally the wrong way to go about things, but that's what we are left with. I can write a lot more about this stuff and how it applies to sensor tilt problems (and other stuff) but I don’t want to write a book here. If you are interested in this stuff and want more, a really good (and readable) handbook is “Field Guide to Optomechanical Design and Analysis” by Katie Schwertz and Jim Burge, published by the SPIE press. Katie’s master’s thesis also contains a lot of useful stuff and it’s worth a look. You can find it here: https://www.optimaxsi.com/wp-content/uploads/2014/01/Useful-Estimations-and-Rules-of-Thumb-for-Optomechanics.pdf - John Edited ... Like

22.76

#...

· 41 likes

A new affliction has recently washed over the world of astro-imaging—namely: sensor tilt. Everywhere I look, sensor tilt is either screwing up an imaging system or it’s being blamed for screwing up an imaging system. And that has led to fixes such as the Octopi camera interface adapter that allow fine adjustment to both sensor spacing and tilt. Faster optical systems and cameras with smaller pixels both work to tighten the requirements on camera tilt and position but to a large extent, the difficulty of aligning cameras has been exacerbated by the really poor mechanical design of many of the components that need to be stacked up in the image train. Poor design is an issue that has caused me to tear my hair out in frustration so many times that I thought I’d post a brief review of common problems along with a very short introduction to optomechanical design principles. My background in optics is primarily in interferometry and optical testing, but I’ve had a serious interest in optomechanics for as long as I can remember. To be clear, the field of optomechanics addresses the specific design challenges associated with optical systems. It involves understanding how to analyze and mount optical components to minimize strain and mechanical distortion, how to achieve and maintain precision alignment, how to select proper materials, how to tolerance mechanical requirements, and how to deal with thermal effects. Lying at the core of all of this, are the basic principles of precision positioning and from what I’ve observed, this is where nearly every (not quite all!) astro-equipment manufacturer falls apart.

Let’s look at just a few examples of poor design that have driven me crazy. Our first example comes from Planewave Instruments. The photos below show the end views of the main dovetail/carriage adapter that they supplied with my 20” telescope back in early 2020. They've shipped a lot of these things and for the life of me, I can’t understand why anyone thinks that it’s acceptable. The mechanics are so faulty that the entire weight of the telescope is held between a couple of pinch points in the carriage and the strength of the connection fall onto the screws themselves. Furthermore, the screws bind so terribly as the dovetail begins to engage that it’s hard to tell when the screws are properly torqued. Grade: D-

As an offer of good will, I suggested the simple design modification shown below to fix the design without having to start completely from scratch. In the end, Planewave declined to fix it so I returned it and replaced the carriage with one from Astro-Physics. The Astro-Physics carriage is beautifully designed and implemented. Designing a well implemented dovetail/carriage is not that hard and in spite of that fact, Planewave isn’t the only company that has had problems pulling it off. I’ve seen similar issues from Celestron with their orange extruded dovetails as well, but I’ve made the point so we’ll skip those photos.

Next on the list: I’ve got a FLI filter wheel for my F/6.7 refractor and for no extra charge, they included a mechanical problem that is so difficult to fix that I had to replace the entire assembly with another brand. In order to try to minimize the thickness of the filter wheel, the FLI design uses only two setscrews located at 120 degrees to mount a dovetail on the camera side of the wheel. The diagram below shows what happens when the screws are tightened. The two sets screws do what they are supposed to do, which is to draw the dovetail down into the mounting hole, but since there is no opposing screw (or lip) on the other side, the camera gets tilted. No amount of shimming will fix this problem! They would have been better off using just a plain cylindrical surface instead of a dovetail. It’s difficult to solve this problem in a clean way without seriously re-machining some of the parts. Grade: F

I replaced the FLI FW with a new one from Pegasus Astro. The Indigo filter wheel mounts 50 mm round filters, it is very inexpensive and at first blush, it looks like a very simple, if not, elegant design. It is very thin, it runs off of USB, and it allows bolting adapters directly to the filter wheel. Unfortunately, it doesn’t take long to uncover multiple problems with this design. First, they use arcing slotted holes to mount adapters and those holes open directly into the filter cavity, which will cover the filters with dust in no short order! What in the world were they thinking??? Fortunately, they designed bolt on covers to cover the holes and as fast as I could complain, they shipped them to me free of charge from Greece. The next problem rears its head when you mount the filters. The diagram below shows the problem.

The screw and washer retainer system is workable but the way that it’s implemented is just sloppy! In my professional life, I’ve shipped optical equipment that I designed all over the world and the first rule is that any screw that isn’t locked, WILL come loose in shipping. Since I’m sending this FW to Chile, I have to address this issue in a serious way.

The final problem with the Indigo FW involves the friction drive wheel on the edge of the filter wheel. It's the blue wheel in the photo above. Unfortunately, they fixed the position of the friction wheel. It’s adjustable for wear, but that’s only possible if you are there—as in when the FW is used in your backyard. That really doesn’t cut it when you are shipping equipment to a very remote location where service can be difficult and where you certainly don’t want to be opening the FW to expose the filters to dust. The drive wheel should have been pre-loaded against the edge of the filter carrier using a simple flexure spring. Additional cost: Very low. As it is, the mechanical design of this product is not very sophisticated. Grade: C-/D+. The good news is that they could clean up this design fairly easily…if they want to.

Last on my list is an issue that probably affects a lot of QHY camera owners. When I switched filter wheels, I had to use the QHY supplied carriage designed to mate to the V-notch “dovetail” on the front of the camera. I was stunned to see just how poorly constrained this whole system is! First, the carriage is seriously over-sized to allow for centering the camera. Let me get something straight here: The only reason you might want to center the camera is if your mechanics are so screwed up in the first place that you can’t mount the carriage where it is supposed to go! More adjustments almost always makes for more misalignment! With this system, it becomes very hard to tell when your camera is precisely centered, but fortunately, centration is not very critical on most systems. Here’s a diagram of how the camera mounts.

The much, much bigger problem is that QHY designed the V-notch spacing so that the centering screws engage it with the camera hanging in space—referenced to absolutely nothing! The centering screws are mounted in loose fit threaded holes and the tips of the screws aren’t coned or spherical. There is simply nothing that defines the angle of the camera! It might be close enough but more likely, the camera will be tilted a bit, no matter what you do. So, in the end you can’t tell when the camera is centered and you sure as heck can’t tell if it’s tilted either. Furthermore, the spacing from the front surface of the V-notch carriage to the sensor depends on how well the screw hole positions are controlled and on the unknown shape of the screw-tips. This is just a mess. The guys at QHY appear to be experts at electronics but in my opinion, their opto-mechanical skills are seriously flawed. No wonder so many folks are buying Ocupi adjusters! Grade for the QHY V-notch mount: F-

Fortunately, there is an easy fix to better control the tilt of the camera shown in the diagram below. First, a conical tip can be ground onto the tip of the centering screws. Second, by carefully measuring the top gap between the V-tail adapter face and the V-tail carriage (using feeler gauges), a circular washer can be cut from plastic shim stock with a bit of extra thickness (maybe 0.010” to 0.015”) to allow the centering screws to contact the bottom edge of the V-notch to pull the V-notch adapter face tight against the shim washer. Astro-Physics uses a V-notch system on their field flatteners but they’ve implemented it correctly so that the retaining screws only engage one edge of the V-notch pulling the adapter and mount tightly together along a reference surface. The diagram below shows the fix. Alternatively, the holes for the screws could be repositioned using a mill and an index table, but that's a lot more work. I'll do it if I need to move the camera inward. The ultimate fix would be to just redesign that whole front V-notch part to be a straight dove-tail...as it should have been in the first place!

Finally, I’ll give an honorable-mention to Celestron for their utterly poor mechanical design of the secondary mount on their Edge series of SCTs.  That design is not well constrained in angle or position and that results in having to realign the secondary every time it is removed or after something as simple as a car trip. Years ago, I completely redesigned the secondary mount on my prototype C14 using kinematic principles and demonstrated on an interferometer that it could hold alignment to within about 5 fringes across the pupil even after pulling the secondary out and remounting it. (The factory version controlled tilt 20-40 times worse!). It had super easy to use, orthogonal tilt adjustment and using CNC, it could be made for only a few more dollars than the existing design.  I offered the design to Celestron but it wasn’t worth it to them so they passed. Too bad. It worked incredibly well and the added cost would have been minimal.

What’s the solution?
I’ve tossed out a lot of examples of poor designs but I don’t want it to sound like all problem and no solution. So, let’s look at a few basic design principles that hopefully will begin to seep into the Astro-Equipment market.

Kinematic Constraint
A rigid body has six degrees of freedom, which includes 3 translational and 3 rotational axis.  A degree of freedom can be controlled by connecting it to a rigid mechanical constraint.  The principle of kinematic constraint is to control any unwanted motion (in position or angle) along a single degree of freedom with a single constraint.  A kinematic constraint is geometrically defined and repeatable to a high degree of accuracy—often limited only by the mechanical stiffness of the constraint itself.  A degree of freedom is over-constrained when more than a single constraint controls motion along that particular axis.  Over constraint causes binding, distortion, and can lead to poor positional performance.  In the worst case, it can also allow unwanted motion along that axis.  More is not always better!

Let’s look at some quick, very simple examples of kinematic constraint.

1)    A perfect ball on a perfect flat surface constrains a single degree of freedom
2)    A high precision ball bearing rolling in a precision ground V-groove constrains two translational degrees of freedom so that the ball can only roll along a single axis.
3)    A single ball in point contact with three balls restrained within a circular ring constrains all three degrees of translational freedom.

While we are at it, here are some common non-kinematic design choices.

1)    Attaching one flat plate to another to constrain tilt.  Any departure from flat in the way of high points (or from contamination such as dirt on the surface) makes the angle uncertain.  There is no way to tell how the plates contact.  Yes, you can lap them together and you can go to a lot of trouble to reduce errors but no matter how careful you are the repeatability and accuracy of controlling angle by mating two large area surfaces will be limited.  Another form of this method is to butt two edges together.  Again, this is not a kinematic solution.
2)    Bolting one plate to another to control position.  Bolt holes are oversized and bolt sizes vary.  Bolting two plates together simply connects them with very little position control.
3)    Controlling angle with two widely separated pins that fit into mating precision holes.  This is an example of an over-constrained design.  The pins and holes have to be co-aligned and the hole spacing has to perfectly match the pin spacing.  Furthermore, a pin in a hole does not precisely control the position of the mating parts. This is what diamond pins are made for!

Pseudo or Semi-Kinematic Design
Psuedo Kinematic design uses the same geometry and concepts at a pure kinematic design but allows for very small over-constraint.  For example, in order to control the tilt of a flat surface, you would ideally place it in contact with three non-linear rigid balls (for single point contact).  However, space or cost constraints may make it difficult to implement a full kinematic design.  In that case, you might simply machine the mounting base to include three very small raised rectangular pads for the mating surface to mount to.  Since the raised pads do not provide a single point of contact, they over-constrain the solution.  However, this kind of pseudo-kinematic approach can improve mechanical performance enormously over a totally non-kinematic solution. If you want to connect the two surfaces, placing a connecting screw through the raised pads minimizes the mechanical distortion of either plate.

Another not so obvious example of a psuedo-kinematic constraint is a ball in a conical hole.  The problem is that a ball intercepts a cone along a circle and you don’t have a way to generate a geometrically perfect conical hole.  The true kinematic solution constrains the ball position using point contact with three touching balls below.

When carefully applied, psuedo-kinematics can solve a LOT of the issues that I've listed here without adding significant to the cost of a product.

Conclusion
It is unfortunate that there appear to be so few companies in the astro-equipment world that are even aware of kinematic design. Worse, as I've mentioned, I've even tried to help a few of them with their design problems and I've been turned down. So, I get the impression that it's not a very high priority to get the mechanics right. That means that we customers are often left dealing with marginal designs--even from high end companies! In my experience, the one company that works very hard to produce excellent mechanics is Astro-Physics. Their designs are almost always spot on. I want to add that I haven't examined products from every company so I'm sure that there are others out there who are paying attention to the mechanics as well. Telescope and equipment alignment would be far, far easier and more precise if more components were properly designed and made! Starting with something that's a mess and then having to add another adjuster to compensate for all of the errors is fundamentally the wrong way to go about things, but that's what we are left with.

I can write a lot more about this stuff and how it applies to sensor tilt problems (and other stuff) but I don’t want to write a book here.  If you are interested in this stuff and want more, a really good (and readable) handbook is “Field Guide to Optomechanical Design and Analysis” by Katie Schwertz and Jim Burge, published by the SPIE press.  Katie’s master’s thesis also contains a lot of useful stuff and it’s worth a look.  You can find it here:  https://www.optimaxsi.com/wp-content/uploads/2014/01/Useful-Estimations-and-Rules-of-Thumb-for-Optomechanics.pdf

- John

Edited ...

6.08 Bob Lockwood #... · view views · 2 likes
John, finely, you nailed it. All the talk about tilt is explained here. Most everyone thinks sensor tilt is a camera issue, ZWO and QHY even sell and put tilt adjusters on their cameras, the camera is not the issue, it's the image train and everything that attaches the scope to the mount. Being a machinist, I know that these camera components are most likely made on a CNC mill and it's highly unlikely that the chip can even be mounted with tilt. I make as much as I can for my image train, and everything is designed using Astro-Physics as a model, I even removed the stock Feather-Touch 3545 focuser and the TEC focuser from my TEC scopes and replaced them with threaded adapters I made then attached the FLI Atlas focuser to each of them. The Astro-Physics V-notch system is applied to all my adapters, even the OAG I made attaches with the V-notch and 6 setscrews, the only thing I wasn't aware of is the FLI FW issue you talked about. I think that may be hit or miss depending on the camera, but in my case, I use the FLI PL camera and in addition to the two setscrews located at 120 apart, the camera has two bolts that run through the camera and into the FW, about as solid as it gets, I think. Anyway, you presented the issue perfectly, I hope that some of the manufacture take note and start making things right, instead of making them as cheap as possible just to make a profit. If you want to see my setups/image train, just open any of my images hear and click on my website links and go to my equipment page. -Bob Edited ... Like

6.08

Bob Lockwood

#...

· 2 likes

John, finely, you nailed it.

All the talk about tilt is explained here. Most everyone thinks sensor tilt is a camera issue, ZWO and QHY even sell and put tilt adjusters on their cameras, the camera is not the issue, it's the image train and everything that attaches the scope to the mount. Being a machinist, I know that these camera components are most likely made on a CNC mill and it's highly unlikely that the chip can even be mounted with tilt. I make as much as I can for my image train, and everything is designed using Astro-Physics as a model, I even removed the stock Feather-Touch 3545 focuser and the TEC focuser from my TEC scopes and replaced them with threaded adapters I made then attached the FLI Atlas focuser to each of them. The Astro-Physics V-notch system is applied to all my adapters, even the OAG I made attaches with the V-notch and 6 setscrews, the only thing I wasn't aware of is the FLI FW issue you talked about. I think that may be hit or miss depending on the camera, but in my case, I use the FLI PL camera and in addition to the two setscrews located at 120 apart, the camera has two bolts that run through the camera and into the FW, about as solid as it gets, I think. Anyway, you presented the issue perfectly, I hope that some of the manufacture take note and start making things right, instead of making them as cheap as possible just to make a profit.
If you want to see my setups/image train, just open any of my images hear and click on my website links and go to my equipment page.

-Bob

Edited ...

0.90 Ped #... · view views
John, you've managed to summarise my frustrations perfectly with this post - excellent! I've just received the Pegasus Indigo FW and, upon your advice in our prior conversation regarding the slotted arcs, reached out to Pegasus. They're sending me anodized aluminium flanges to correct the issue, but I'll have to pay for shipping. Should have been there in the first place, but good customer service from them nonetheless. I've also reached out to Joel (Buckeyestargazer) to order 3d printed filter centering masks. Hopefully this will correct the issue of the angled washers. Like

0.90

Ped

#...

John, you've managed to summarise my frustrations perfectly with this post - excellent!

I've just received the Pegasus Indigo FW and, upon your advice in our prior conversation regarding the slotted arcs, reached out to Pegasus. They're sending me anodized aluminium flanges to correct the issue, but I'll have to pay for shipping. Should have been there in the first place, but good customer service from them nonetheless. I've also reached out to Joel (Buckeyestargazer) to order 3d printed filter centering masks. Hopefully this will correct the issue of the angled washers.

22.76 John Hayes #... · view views
Bob Lockwood: John, finely, you nailed it. All the talk about tilt is explained here. Most everyone thinks sensor tilt is a camera issue, ZWO and QHY even sell and put tilt adjusters on their cameras, the camera is not the issue, it's the image train and everything that attaches the scope to the mount. Being a machinist, I know that these camera components are most likely made on a CNC mill and it's highly unlikely that the chip can even be mounted with tilt. I make as much as I can for my image train, and everything is designed using Astro-Physics as a model, I even removed the stock Feather-Touch 3545 focuser and the TEC focuser from my TEC scopes and replaced them with threaded adapters I made then attached the FLI Atlas focuser to each of them. The Astro-Physics V-notch system is applied to all my adapters, even the OAG I made attaches with the V-notch and 6 setscrews, the only thing I wasn't aware of is the FLI FW issue you talked about. I think that may be hit or miss depending on the camera, but in my case, I use the FLI PL camera and in addition to the two setscrews located at 120 apart, the camera has two bolts that run through the camera and into the FW, about as solid as it gets, I think. Anyway, you presented the issue perfectly, I hope that some of the manufacture take note and start making things right, instead of making them as cheap as possible just to make a profit. If you want to see my setups/image train, just open any of my images hear and click on my website links and go to my equipment page. -Bob Thanks Bob! I’m envious…I sure wish that I had at least a good mill and lathe in my shop. I’d really like to have a CNC machine! As it is I have to use service like Xometry to make my custom parts. I’m pretty certain that if you can control the tolerances on all of the parts between the telescope and the camera, there wouldn’t be any issues with tilt down to about F/6–even at very wide fields. I think that at faster speeds the amount of tilt adjustment that you might need would be very small and easily solved with some thin shims. While I’m at it, my other optomechanical pet peeve is the use of equi-spaced, 3-screw tilt adjustment mechanisms. It seems like no one in the world of astronomy has ever used a tip-tilt mount with orthogonal adjustments! Orthogonal adjustments are FAR easier to use than a non-orthogonal 3-screw system and they are no harder to make. Why in the world are we still stuck with 3-screw tilt adjustments on various critical components? John Like

22.76

John Hayes

#...

Bob Lockwood:
John, finely, you nailed it.

All the talk about tilt is explained here. Most everyone thinks sensor tilt is a camera issue, ZWO and QHY even sell and put tilt adjusters on their cameras, the camera is not the issue, it's the image train and everything that attaches the scope to the mount. Being a machinist, I know that these camera components are most likely made on a CNC mill and it's highly unlikely that the chip can even be mounted with tilt. I make as much as I can for my image train, and everything is designed using Astro-Physics as a model, I even removed the stock Feather-Touch 3545 focuser and the TEC focuser from my TEC scopes and replaced them with threaded adapters I made then attached the FLI Atlas focuser to each of them. The Astro-Physics V-notch system is applied to all my adapters, even the OAG I made attaches with the V-notch and 6 setscrews, the only thing I wasn't aware of is the FLI FW issue you talked about. I think that may be hit or miss depending on the camera, but in my case, I use the FLI PL camera and in addition to the two setscrews located at 120 apart, the camera has two bolts that run through the camera and into the FW, about as solid as it gets, I think. Anyway, you presented the issue perfectly, I hope that some of the manufacture take note and start making things right, instead of making them as cheap as possible just to make a profit.
If you want to see my setups/image train, just open any of my images hear and click on my website links and go to my equipment page.

-Bob

Thanks Bob! I’m envious…I sure wish that I had at least a good mill and lathe in my shop. I’d really like to have a CNC machine! As it is I have to use service like Xometry to make my custom parts. I’m pretty certain that if you can control the tolerances on all of the parts between the telescope and the camera, there wouldn’t be any issues with tilt down to about F/6–even at very wide fields. I think that at faster speeds the amount of tilt adjustment that you might need would be very small and easily solved with some thin shims.

While I’m at it, my other optomechanical pet peeve is the use of equi-spaced, 3-screw tilt adjustment mechanisms. It seems like no one in the world of astronomy has ever used a tip-tilt mount with orthogonal adjustments! Orthogonal adjustments are FAR easier to use than a non-orthogonal 3-screw system and they are no harder to make. Why in the world are we still stuck with 3-screw tilt adjustments on various critical components?

John

22.76 John Hayes #... · view views
John, you've managed to summarise my frustrations perfectly with this post - excellent! I've just received the Pegasus Indigo FW and, upon your advice in our prior conversation regarding the slotted arcs, reached out to Pegasus. They're sending me anodized aluminium flanges to correct the issue, but I'll have to pay for shipping. Should have been there in the first place, but good customer service from them nonetheless. I've also reached out to Joel (Buckeyestargazer) to order 3d printed filter centering masks. Hopefully this will correct the issue of the angled washers. Thanks Ped! I’ll have to look into Buckeystargazer to see what he can do before I design my own parts. John Like

22.76

John Hayes

#...

John, you've managed to summarise my frustrations perfectly with this post - excellent!

I've just received the Pegasus Indigo FW and, upon your advice in our prior conversation regarding the slotted arcs, reached out to Pegasus. They're sending me anodized aluminium flanges to correct the issue, but I'll have to pay for shipping. Should have been there in the first place, but good customer service from them nonetheless. I've also reached out to Joel (Buckeyestargazer) to order 3d printed filter centering masks. Hopefully this will correct the issue of the angled washers.

Thanks Ped! I’ll have to look into Buckeystargazer to see what he can do before I design my own parts.

John

1.20 frankszabo75 #... · view views
While not related to various dove tail or other designs, my first impression just shortly after I started imaging, that the compression copper ring-style connections are very unreliable. Working ok maybe for visual observing, but it's stone-age accuracy for imaging applications. I know, many people don't use rotators (or can't, because there is no more space between camera and flattener), so many people end up rotating their camera by loosening the flattener in the focuser and re-tighten. (I also have an issue with rotators, how they can be also add tilt, because of imprecise manufacturing) Even tiny misalignment caused by compression rings will cause a tilt in the image train. This is almost unavoidable and some companies like Hotech tried to combat this with a self-centering /expanding fitment type, which -again- might not be as accurate as threaded applications. Focuser tubes, despite having that 2" (or 3") standard size still vary and so do various flatteners. I fail to saee how they can't just be more precise with this! Is it really difficult to make a 2" piece of tube so it's not 2.1 or 1.9 in diameter? I could've said it metric, it doesn't matter. I recently bought a few T-mounts for my Canon for example. 3 different brands- 3 different prices- same Canon EOS T mount. I returned all 3 and and start to have serious doubt that anyone can manufacture things to specs. I just won't be able to use a DSLR, because of this and no , spending $90 (my 4th choice) for a piece of aluminum with threads cut into is also not the solution. It does not cost that much to replicate something with modern precision- manufacturing. 1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine. 2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter. 3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter. I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way. I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?) I've come across items that were manufactured 100 years ago more accurately, than things I can buy today. I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software. My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right? This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for. Edited ... Like

1.20

frankszabo75

#...

While not related to various dove tail or other designs, my first impression just shortly after I started imaging, that the compression copper ring-style connections are very unreliable. Working ok maybe for visual observing, but it's stone-age accuracy for imaging applications.
I know, many people don't use rotators (or can't, because there is no more space between camera and flattener), so many people end up rotating their camera by loosening the flattener in the focuser and re-tighten. (I also have an issue with rotators, how they can be also add tilt, because of imprecise manufacturing) Even tiny misalignment caused by compression rings will cause a tilt in the image train. This is almost unavoidable and some companies like Hotech tried to combat this with a self-centering /expanding fitment type, which -again- might not be as accurate as threaded applications.
Focuser tubes, despite having that 2" (or 3") standard size still vary and so do various flatteners. I fail to saee how they can't just be more precise with this! Is it really difficult to make a 2" piece of tube so it's not 2.1 or 1.9 in diameter? I could've said it metric, it doesn't matter.
I recently bought a few T-mounts for my Canon for example. 3 different brands- 3 different prices- same Canon EOS T mount. I returned all 3 and and start to have serious doubt that anyone can manufacture things to specs. I just won't be able to use a DSLR, because of this and no , spending $90 (my 4th choice) for a piece of aluminum with threads cut into is also not the solution. It does not cost that much to replicate something with modern precision- manufacturing.
1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine.
2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter.
3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter.
I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way.
I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?)
I've come across items that were manufactured 100 years ago more accurately, than things I can buy today.
I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software.
My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right?
This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for.

Edited ...

3.58 David Moore #... · view views
John, That's a very interesting article and thanks for sharing. It reminds me of problems I have had with the focusser on my Skywatcher 130PDS and 200PDS Newtonians. The tube has a screw on end piece which is greater internal diameter, so when my long barrel Explorer Scientific coma corrector is inserted, it is hanging unsupported at the scope end and even trying to butt it up tight does not guarantee centrallity. The end result is tilt. I tried replacing the end piece with an adaptor that had a ring that is tightened up to the corrector with 2 screws and I even tapped a hole in it and inserted an M4 screw so each screw was 120 degrees apart, to provide even tightening and tilt was worse. I then stuck 3 pieces of tape at the scope end of the focusser tube, 120 degrees apart to take up the slack and that was an improvement. Unfortunately it doesn't take up all the slack. Another focusser is the only way out without workshop support. That brings me to another point. Skywatcher is one manufacturer and Explorer Scientific is another. If both were the same company then they could arrange that the corrector screwed into the focusser or it could be made a sliding fit. Skywatcher do make a coma corrector which slides into the focusser as mine does, though it is a lot shorter. I have no experience of it though. The fact that my cameras are APS-C type makes round corner stars harder to achieve than with smaller sensors. I used to use a full format DSLR and that always gave me corner star issues. Lacerta, for example, have a 10" F4 Newt and tailor the corrector to fit their focusser properly and seem to have gone to a lot of trouble with their focusser to make sure it has no tilt and does not droop under load. It looks like they have done some good design work though I do not have any of their equipment and have no connection with them. They also have spent a lot of time on their main mirror support. I like good design work. I have 2 ZWO ASI 2600MC/MM cameras. Two have gone back with grease in the sensor and 1 with a temp sensor fault that developed. ZWO acknowledged the grease problem publically some time ago and anyone having this issue has a lifetime guarantee that they will fix it. That is a design issue. One more thing is quality control as well as design. I had to return 2 Skywatcher 130PDS scopes as there was a particular weakness in the packaging that meant the scopes were damaged in transit twice in the same place. In my work I used to help evaluate instrumentation and manufactures claims and specifications in real world outdoor conditions and feed back any issues to them. Sometimes it used to feel that we were their final QA division. It is a great pity that manufacturers have spurned your design expertise and vast experience and not improved their designs as that would ultimately have helped everyone and increased their reputation and sales. I used to visit trade exhibitions of instrumentation (not astronomical) where manufacturers and users could mingle and learn from each other. Perhaps this happens in the USA? There is one such venue in the UK that I am aware of. Like

3.58

David Moore

#...

John,
That's a very interesting article and thanks for sharing.
It reminds me of problems I have had with the focusser on my Skywatcher 130PDS and 200PDS Newtonians. The tube has a screw on end piece which is greater internal diameter, so when my long barrel Explorer Scientific coma corrector is inserted, it is hanging unsupported at the scope end and even trying to butt it up tight does not guarantee centrallity. The end result is tilt.
I tried replacing the end piece with an adaptor that had a ring that is tightened up to the corrector with 2 screws and I even tapped a hole in it and inserted an M4 screw so each screw was 120 degrees apart, to provide even tightening and tilt was worse. I then stuck 3 pieces of tape at the scope end of the focusser tube, 120 degrees apart to take up the slack and that was an improvement. Unfortunately it doesn't take up all the slack. Another focusser is the only way out without workshop support.

That brings me to another point. Skywatcher is one manufacturer and Explorer Scientific is another. If both were the same company then they could arrange that the corrector screwed into the focusser or it could be made a sliding fit. Skywatcher do make a coma corrector which slides into the focusser as mine does, though it is a lot shorter. I have no experience of it though.

The fact that my cameras are APS-C type makes round corner stars harder to achieve than with smaller sensors. I used to use a full format DSLR and that always gave me corner star issues.

Lacerta, for example, have a 10" F4 Newt and tailor the corrector to fit their focusser properly and seem to have gone to a lot of trouble with their focusser to make sure it has no tilt and does not droop under load. It looks like they have done some good design work though I do not have any of their equipment and have no connection with them. They also have spent a lot of time on their main mirror support.
I like good design work.

I have 2 ZWO ASI 2600MC/MM cameras. Two have gone back with grease in the sensor and 1 with a temp sensor fault that developed. ZWO acknowledged the grease problem publically some time ago and anyone having this issue has a lifetime guarantee that they will fix it. That is a design issue.

One more thing is quality control as well as design. I had to return 2 Skywatcher 130PDS scopes as there was a particular weakness in the packaging that meant the scopes were damaged in transit twice in the same place.

In my work I used to help evaluate instrumentation and manufactures claims and specifications in real world outdoor conditions and feed back any issues to them. Sometimes it used to feel that we were their final QA division. It is a great pity that manufacturers have spurned your design expertise and vast experience and not improved their designs as that would ultimately have helped everyone and increased their reputation and sales.
I used to visit trade exhibitions of instrumentation (not astronomical) where manufacturers and users could mingle and learn from each other. Perhaps this happens in the USA? There is one such venue in the UK that I am aware of.

6.08 Bob Lockwood #... · view views · 1 like
precision- manufacturing. 1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine. 2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter. 3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter. I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way. I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?) I've come across items that were manufactured 100 years ago more accurately, than things I can buy today. I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software. My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right? This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for. frankszabo75, I couldn't agree with you more, but first, when you mention 2" aluminum tube that could be 1.9 to 2.1, that can't happen. Aluminum Tubing has to follow an AMS spec that has a tolerance of +- .005" even if you get tubing that has threads on its end it still follows the AMS spec. Don't confuse tubing with pipe, big difference in the two, but all this is as you said, it beside the point. Buying threaded parts is a big issue in my book, it's not the thread, it's the machine doing the threading. All machines wear differently over time and unless the equipment is following an aircraft 9100 spec, there probably never checked. A threaded part from one place even following the thread spec, say an M48 or M42 from two difference places could be way different. Precise-Parts has a big issue with this, I got an adapter from them for testing a spacer I was going to make, it was an end cap for the FT3545 focuser that had FLI dovetail on it. When I got it I checked the threads on the O.D. of the focuser and the I.D of the PP adapter and there was only a total of .010" of thread contact, I could have pulled the adapter off by hand if I tried, I think that's common in just about all their adapters. That's why I do all my owe threading and check the fit as I go. I think the issue is that each company may or may not intentionally cut their threads on the loose side so that they dont lock up on another company's threads. Unfortunately, not many have that option of doing their own threading. Like

6.08

Bob Lockwood

#...

· 1 like

precision- manufacturing.
1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine.
2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter.
3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter.
I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way.
I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?)
I've come across items that were manufactured 100 years ago more accurately, than things I can buy today.
I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software.
My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right?
This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for.

frankszabo75,

I couldn't agree with you more, but first, when you mention 2" aluminum tube that could be 1.9 to 2.1, that can't happen. Aluminum Tubing has to follow an AMS spec that has a tolerance of +- .005" even if you get tubing that has threads on its end it still follows the AMS spec. Don't confuse tubing with pipe, big difference in the two, but all this is as you said, it beside the point. Buying threaded parts is a big issue in my book, it's not the thread, it's the machine doing the threading. All machines wear differently over time and unless the equipment is following an aircraft 9100 spec, there probably never checked. A threaded part from one place even following the thread spec, say an M48 or M42 from two difference places could be way different. Precise-Parts has a big issue with this, I got an adapter from them for testing a spacer I was going to make, it was an end cap for the FT3545 focuser that had FLI dovetail on it. When I got it I checked the threads on the O.D. of the focuser and the I.D of the PP adapter and there was only a total of .010" of thread contact, I could have pulled the adapter off by hand if I tried, I think that's common in just about all their adapters. That's why I do all my owe threading and check the fit as I go. I think the issue is that each company may or may not intentionally cut their threads on the loose side so that they dont lock up on another company's threads. Unfortunately, not many have that option of doing their own threading.

11.99 Arun H #... · view views · 1 like
I know, many people don't use rotators (or can't, because there is no more space between camera and flattener), so many people end up rotating their camera by loosening the flattener in the focuser and re-tighten. (I also have an issue with rotators, how they can be also add tilt, because of imprecise manufacturing) Even tiny misalignment caused by compression rings will cause a tilt in the image train. Couldn't agree more. It isn't just that they cause tilt, it is that they cause varying and non repeatable amounts of tilt. If there was a way to assure it was repeatable, it could be handled, but there doesn't seem to be. On the topic of Astro-Physics: I suspect part of the reason why their equipment is mechanically and optically so good is that Roland is an imager, so he knows what it takes. They have made mistakes, but it is usually possible to have data based discussions with them and once they know it is an issue, they will own up to it and correct it. Edited ... Like

11.99

Arun H

#...

· 1 like

I know, many people don't use rotators (or can't, because there is no more space between camera and flattener), so many people end up rotating their camera by loosening the flattener in the focuser and re-tighten. (I also have an issue with rotators, how they can be also add tilt, because of imprecise manufacturing) Even tiny misalignment caused by compression rings will cause a tilt in the image train.

Couldn't agree more. It isn't just that they cause tilt, it is that they cause varying and non repeatable amounts of tilt. If there was a way to assure it was repeatable, it could be handled, but there doesn't seem to be.

On the topic of Astro-Physics: I suspect part of the reason why their equipment is mechanically and optically so good is that Roland is an imager, so he knows what it takes. They have made mistakes, but it is usually possible to have data based discussions with them and once they know it is an issue, they will own up to it and correct it.

Edited ...

1.20 frankszabo75 #... · view views
Bob Lockwood: precision- manufacturing. 1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine. 2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter. 3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter. I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way. I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?) I've come across items that were manufactured 100 years ago more accurately, than things I can buy today. I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software. My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right? This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for. frankszabo75, I couldn't agree with you more, but first, when you mention 2" aluminum tube that could be 1.9 to 2.1, that can't happen. Well, I was exaggerating a bit, but there has been plenty examples of if someting is 2" OD vs. 2" ID just don't fit. I have diagonals, Cheshire tools, lasers and eyepieces, flatteners and also have 4 telescopes and some fit tight in one will be loose in the other. I wouldn't call it "cheap", because 2 of my coma correctors beyond $300 and some of the eyepieces aren't cheap either. So it's either the accessories or the scope focusers. Someone is slacking on the exact measurements. Like

1.20

frankszabo75

#...

Bob Lockwood:
precision- manufacturing.
1- was already loose on the camera, clicking left/right- not sitting well. I triple checked if my camera has a bad bayonet mount, but no, all the canon lens I have sit solidly on without any play, so the camera is fine.
2nd - wouldn't thread on a 42mm straight. I tested the 42mm threading on the flattener, it's absolutely good, since I can thread on any extension tubes without trouble. But not the T-Canon adapter.
3rd - a 48mm version of the T adapter. Same issue. Wouldn't thread on straight and the camera was also loose on the adapter.
I had similar adventure using W.Optics Zenithstar telescope and their very loosely made flattener, which not only produced a tilt by having the adjustable part loose, but there was a giant light leak on top, due to a flattened part over the threads, which I have no idea why it had to be that way.
I wrote a review on all and I asked a serious question, regarding precision. I really thought - cutting accurate threads into a barrel was solved in the 19th century (or even earlier?)
I've come across items that were manufactured 100 years ago more accurately, than things I can buy today.
I understand mass production, what I don't understand, that it seems like we are going backward, while making precision manufacturing supposed to be easier with laser precision and software.
My older brother has experience using a CNC machine and he is a mechanic and many times he ends up manufacturing the parts (or tools) he needs, because he can't find an accurately manufactured part or tool. I'm not talking about super-precision. I'm talking about having things screw together with threads, as they should. This is very basic, very primitive the dawn of the manufacturing era, where threads catch on each other, there is no magic involved. Right?
This shouldn't be an issue in the 21st century, yet it is and I am convinced it's not the machines, but the humans involved producing junk, because quality control seems to be non-existent or proved to be some sort of an extra expense that companies no longer want to pay for.

frankszabo75,

I couldn't agree with you more, but first, when you mention 2" aluminum tube that could be 1.9 to 2.1, that can't happen.

Well, I was exaggerating a bit, but there has been plenty examples of if someting is 2" OD vs. 2" ID just don't fit. I have diagonals, Cheshire tools, lasers and eyepieces, flatteners and also have 4 telescopes and some fit tight in one will be loose in the other. I wouldn't call it "cheap", because 2 of my coma correctors beyond $300 and some of the eyepieces aren't cheap either. So it's either the accessories or the scope focusers. Someone is slacking on the exact measurements.

4.88 Aygen #... · view views · 1 like
Incredible write-up, John !!!!! I feel somewhat lucky to be part of such a great community with so many intelligent people - I keep learning every day. Also, as you well mentioned, there are only a few Companies that really produce high end products (Astro-physics, for instance). Edited ... Like

6.06 Matthew Proulx #... · view views
I’m glad you opened this topic. My frustrations have primarily been in mirror cell support for my 12” and sensor tilt but there have been others. I cannot believe how many people are accepting of the rubbish that passes off in this field. Ignorance is bliss I suppose. My trade is millwright where precision alignment is the second most important factor, next to precision made parts. Whether it’s a simple dovetail or a million dollar gas turbine makes no difference, The smallest fault in tolerances will hinder your ability to meet spec 100% of the time. The worst part of all of this is, even custom parts makers will not take any feedback. Their ignorant blissful customers make them think they’re doing something right. Like

6.06

Matthew Proulx

#...

I’m glad you opened this topic. My frustrations have primarily been in mirror cell support for my 12” and sensor tilt but there have been others. I cannot believe how many people are accepting of the rubbish that passes off in this field. Ignorance is bliss I suppose. My trade is millwright where precision alignment is the second most important factor, next to precision made parts. Whether it’s a simple dovetail or a million dollar gas turbine makes no difference, The smallest fault in tolerances will hinder your ability to meet spec 100% of the time.

The worst part of all of this is, even custom parts makers will not take any feedback. Their ignorant blissful customers make them think they’re doing something right.

22.76 John Hayes #... · view views
On the topic of Astro-Physics: I suspect part of the reason why their equipment is mechanically and optically so good is that Roland is an imager, so he knows what it takes. I think that that's true. Roland also worked on cars and through that he became a student of good mechanics. He is very proud of his designs and he has eagerly shown me little special features that he clearly thought a lot about. Getting a design right is more than a job; it's a passion...and Roland has it. To be fair to Planewave, they have done some really outstanding engineering on many of their products. For example, the L-series mount are very well engineered. I think that sometimes they are victims of their own success. Fighting the latest fire and getting products shipped take priority over developing a quality system that values continuous improvement. I've been there, done that so I understand the challenges, but why would anyone turn down the offer of *free* help to fix a mostly minor problem that no one else has time to fix??? At the time, they even acknowledged that they knew about the problem with their dovetail design. That's NIH taken to an extreme level! John Like

22.76

John Hayes

#...

On the topic of Astro-Physics: I suspect part of the reason why their equipment is mechanically and optically so good is that Roland is an imager, so he knows what it takes.

I think that that's true. Roland also worked on cars and through that he became a student of good mechanics. He is very proud of his designs and he has eagerly shown me little special features that he clearly thought a lot about. Getting a design right is more than a job; it's a passion...and Roland has it.

To be fair to Planewave, they have done some really outstanding engineering on many of their products. For example, the L-series mount are very well engineered. I think that sometimes they are victims of their own success. Fighting the latest fire and getting products shipped take priority over developing a quality system that values continuous improvement. I've been there, done that so I understand the challenges, but why would anyone turn down the offer of free help to fix a mostly minor problem that no one else has time to fix??? At the time, they even acknowledged that they knew about the problem with their dovetail design. That's NIH taken to an extreme level!

John

11.02 Bill Long - Dark Matters Astrophotography #... · view views · 1 like
John Hayes: The screw and washer retainer system is workable but the way that it’s implemented is just sloppy! In my professional life, I’ve shipped optical equipment that I designed all over the world and the first rule is that any screw that isn’t locked, WILL come loose in shipping. Since I’m sending this FW to Chile, I have to address this issue in a serious way. You can print these for the Indigo Wheel: 50mm_Mask.stl This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point. Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design. Edited ... Like

11.02

Bill Long - Dark Matters Astrophotography

#...

· 1 like

John Hayes:
The screw and washer retainer system is workable but the way that it’s implemented is just sloppy! In my professional life, I’ve shipped optical equipment that I designed all over the world and the first rule is that any screw that isn’t locked, WILL come loose in shipping. Since I’m sending this FW to Chile, I have to address this issue in a serious way.

You can print these for the Indigo Wheel: 50mm_Mask.stl

This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point.

Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design.

Edited ...

22.76 John Hayes #... · view views · 1 like
You can print these for the Indigo Wheel: 50mm_Mask.stl This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point. Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design. Thanks Bill! That looks perfect! Before I have the parts made, can you confirm that the file is for 3 mm thick, unmounted filters? If so, I'll get 7 of those things made ASAP. Does it allow fully tightening the screws? (I can Lock-Tite if not). Did you make it with a light or solid fill? (I'm inclined to go with solid.) John Edited ... Like

22.76

John Hayes

#...

· 1 like

You can print these for the Indigo Wheel: 50mm_Mask.stl

This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point.

Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design.

Thanks Bill! That looks perfect! Before I have the parts made, can you confirm that the file is for 3 mm thick, unmounted filters? If so, I'll get 7 of those things made ASAP. Does it allow fully tightening the screws? (I can Lock-Tite if not). Did you make it with a light or solid fill? (I'm inclined to go with solid.)

John

Edited ...

11.02 Bill Long - Dark Matters Astrophotography #... · view views
John Hayes: You can print these for the Indigo Wheel: 50mm_Mask.stl This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point. Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design. Thanks Bill! Before I have the parts made, can you confirm that the file is for 3 mm thick, unmounted filters? If so, I'll get 7 of those things made ASAP. John Correct. I've tested them with both the Chromas (LRGB + 3nm SHO) and Astronomik Deep Sky RGB and MaxFR filters -- both sets in 50mm round. The masks work perfectly with those filter sets. Edited ... Like

11.02

Bill Long - Dark Matters Astrophotography

#...

John Hayes:
You can print these for the Indigo Wheel: 50mm_Mask.stl

This should help ensure the filters are well secured. I have the metal replacements for the wheel inner rings to cover the slots when using bolted connections, I plan to swap them in for my 3D printed ones, which do seem to have worked well to this point.

Great writeup on the design shortcomings of Astro gear. With my Epsilon I have had to replace all sorts of components due to bad design.

Thanks Bill! Before I have the parts made, can you confirm that the file is for 3 mm thick, unmounted filters? If so, I'll get 7 of those things made ASAP.

John

Correct. I've tested them with both the Chromas (LRGB + 3nm SHO) and Astronomik Deep Sky RGB and MaxFR filters -- both sets in 50mm round. The masks work perfectly with those filter sets.

Edited ...

22.76 John Hayes #... · view views · 1 like
Fantastic...thanks! John Like

20.43 Chris White- Overcast Observatory #... · view views · 4 likes
I can confirm that those pegasus masks work very well. FWIW, pegasus did provide the file for those. It's a shame that they and most everyone else seems to only include the crappy little washers for mounting. There has to be what $0.50 worth of material in a set of printed masks like what Bill shared? Seems they would go the extra mile and print them and include them. As far as everything else... I've learned the hard way on a lot of gear that it wasn't up to snuff. I've learned a lot though in the process on how to methodically diagnose where problems lie and how to get creative at mitigating them. I've also made some great friends to collaborate with on how to make things better and how to select gear that is less problematic. I'm currently using a Mach2, 130GTX, e160ed (upgraded) as my primary gear and a bunch of 3rd party accessories for everything else. I'm not remote yet, so the ability to tinker on something is not a hard criteria for me like it is for you John, but the gear I have has been dialed in by me personally and I'm enjoying great results. Not by accident. By getting the best I can afford and putting effort into making it sing. One thing that you touched on is how companies deal with issues when brought to their attention. Many companies dont seem to care while others are eager to provide a solution. I was perhaps the first person to receive an Indigo wheel for example and immediately emailed them about the slotted hole issue. They were on it immediately and fixed the issue by creating machined masks and sent stl files for printed masks while I waited. Now they are including the machined masks with the wheel. That to me goes a long way... if a company is willing to receive feedback and proactively address issues that is important. The companies that dont seem to care... I never go back to. I'm a discriminating imager and put tremendous effort into getting high quality data. Discriminating imagers should not be the outlier customer for companies making "precision" equipment.... Sadly, some companies have decided that many people are happy with "medeocre quality" and that target audience is large and sustains their profit goals. Edited ... Like

20.43

Chris White- Overcast Observatory

#...

· 4 likes

I can confirm that those pegasus masks work very well. FWIW, pegasus did provide the file for those. It's a shame that they and most everyone else seems to only include the crappy little washers for mounting. There has to be what $0.50 worth of material in a set of printed masks like what Bill shared? Seems they would go the extra mile and print them and include them.

As far as everything else... I've learned the hard way on a lot of gear that it wasn't up to snuff. I've learned a lot though in the process on how to methodically diagnose where problems lie and how to get creative at mitigating them. I've also made some great friends to collaborate with on how to make things better and how to select gear that is less problematic.

I'm currently using a Mach2, 130GTX, e160ed (upgraded) as my primary gear and a bunch of 3rd party accessories for everything else. I'm not remote yet, so the ability to tinker on something is not a hard criteria for me like it is for you John, but the gear I have has been dialed in by me personally and I'm enjoying great results. Not by accident. By getting the best I can afford and putting effort into making it sing.

One thing that you touched on is how companies deal with issues when brought to their attention. Many companies dont seem to care while others are eager to provide a solution. I was perhaps the first person to receive an Indigo wheel for example and immediately emailed them about the slotted hole issue. They were on it immediately and fixed the issue by creating machined masks and sent stl files for printed masks while I waited. Now they are including the machined masks with the wheel. That to me goes a long way... if a company is willing to receive feedback and proactively address issues that is important.

The companies that dont seem to care... I never go back to. I'm a discriminating imager and put tremendous effort into getting high quality data. Discriminating imagers should not be the outlier customer for companies making "precision" equipment.... Sadly, some companies have decided that many people are happy with "medeocre quality" and that target audience is large and sustains their profit goals.

Edited ...

11.02 Bill Long - Dark Matters Astrophotography #... · view views · 1 like
I can confirm that those pegasus masks work very well. FWIW, pegasus did provide the file for those. It's a shame that they and most everyone else seems to only include the crappy little washers for mounting. There has to be what $0.50 worth of material in a set of printed masks like what Bill shared? Seems they would go the extra mile and print them and include them. I don't think it was even 50 cents worth of filament to print 7 of them. I do like that they are very robust though and are designed perfectly for fitting in the slots, nice and flush, with none of the masks bumping into one another. The clear aperture on them is 50mm, so they should not obscure the filter glass at all. Like

11.02

Bill Long - Dark Matters Astrophotography

#...

· 1 like

I can confirm that those pegasus masks work very well. FWIW, pegasus did provide the file for those. It's a shame that they and most everyone else seems to only include the crappy little washers for mounting. There has to be what $0.50 worth of material in a set of printed masks like what Bill shared? Seems they would go the extra mile and print them and include them.

I don't think it was even 50 cents worth of filament to print 7 of them. I do like that they are very robust though and are designed perfectly for fitting in the slots, nice and flush, with none of the masks bumping into one another. The clear aperture on them is 50mm, so they should not obscure the filter glass at all.

8.40 Rouz Astro #... · view views
Nice writeup John. Some very good points! I too get very frustrated with sloppy implementation. I have to agree about the AP gear, I'm very happy with the mechanical quality of the mount/saddle. I feel the APCC software can be more efficient though. Another example was the Pegasus Falcon, I don't see how it can be "flex free" with the specified 15 (or 18)kg payload, it was returned. The smaller 2.75" Hedrick focuser wasn't the stiffest either. The Optec Gemini exceeded my expectations with stiffness! I have promised myself not to ever touch another Explore Scientific (ironic brand name) telescope ever again! The PW CDK14, on the other hand, has been working very well. CS Rouz Like

8.40

Rouz Astro

#...

Nice writeup John. Some very good points!
I too get very frustrated with sloppy implementation. I have to agree about the AP gear, I'm very happy with the mechanical quality of the mount/saddle.
I feel the APCC software can be more efficient though.

Another example was the Pegasus Falcon, I don't see how it can be "flex free" with the specified 15 (or 18)kg payload, it was returned. The smaller 2.75" Hedrick focuser wasn't the stiffest either. The Optec Gemini exceeded my expectations with stiffness!

I have promised myself not to ever touch another Explore Scientific (ironic brand name) telescope ever again! The PW CDK14, on the other hand, has been working very well.

CS
Rouz

8.40 Rouz Astro #... · view views
Another little example, ordered the PW Securefit to M54 adapter. The adapter lip does not fit into the PW reducer groove. Also, the wall thickness of the M54 thread is VERY thick and you loose several mms of clear aperture. I informed them and they said they should update the design. I had to machine it off myself. Like

4.52 Marcelof #... · view views · 1 like
Thank you for taking the time to share the article. Unfortunately very true. And reading it I can't help but think of this, the JWST filter wheel, basically the opposite end of the problem. It's striking how really simple it is, but clearly over engineered. Not only is it completely unreachable for any repair or maintenance, but it must undergo the vibrations of a space launch (and they use some kind of loclite too!). And a video of a working prototype: https://www.youtube.com/watch?v=PSk10ueJcto Like

4.52

Marcelof

#...

· 1 like

Thank you for taking the time to share the article. Unfortunately very true.

And reading it I can't help but think of this, the JWST filter wheel, basically the opposite end of the problem. It's striking how really simple it is, but clearly over engineered. Not only is it completely unreachable for any repair or maintenance, but it must undergo the vibrations of a space launch (and they use some kind of loclite too!).

And a video of a working prototype:

https://www.youtube.com/watch?v=PSk10ueJcto

8.40 Rouz Astro #... · view views · 1 like
On the topic of FW, my QHY FW failed to return properly, the firmware needs to be updated. When it spins in both directions, it doesn't index perfectly: https://www.youtube.com/shorts/i05QISxDGS8 Then after the update, it works perfectly: https://www.youtube.com/watch?v=5lMJS7Loknk Like

20.43 Chris White- Overcast Observatory #... · view views
Rouz Astro: On the topic of FW, my QHY FW failed to return properly, the firmware needs to be updated. When it spins in both directions, it doesn't index perfectly: https://www.youtube.com/shorts/i05QISxDGS8 Then after the update, it works perfectly: https://www.youtube.com/watch?v=5lMJS7Loknk Mine indexed properly after the FW flash, but was off center so had uneven vignetting. Qhy wheel is garbage IMO. Build quality and software... Edited ... Like

20.43

Chris White- Overcast Observatory

#...

Rouz Astro:
On the topic of FW, my QHY FW failed to return properly, the firmware needs to be updated. When it spins in both directions, it doesn't index perfectly:

https://www.youtube.com/shorts/i05QISxDGS8

Then after the update, it works perfectly:
https://www.youtube.com/watch?v=5lMJS7Loknk

Mine indexed properly after the FW flash, but was off center so had uneven vignetting. Qhy wheel is garbage IMO. Build quality and software...

Edited ...

8.40 Rouz Astro #... · view views
Rouz Astro: On the topic of FW, my QHY FW failed to return properly, the firmware needs to be updated. When it spins in both directions, it doesn't index perfectly: https://www.youtube.com/shorts/i05QISxDGS8 Then after the update, it works perfectly: https://www.youtube.com/watch?v=5lMJS7Loknk Mine indexed properly after the FW flash, but was off center so had uneven vignetting. Qhy wheel is garbage IMO. Build quality and software... *After the update, it has been working flawlessly for me. The uneven vignetting was an issue for me as well before the update. Like

8.40

Rouz Astro

#...

Rouz Astro:
On the topic of FW, my QHY FW failed to return properly, the firmware needs to be updated. When it spins in both directions, it doesn't index perfectly:

https://www.youtube.com/shorts/i05QISxDGS8

Then after the update, it works perfectly:
https://www.youtube.com/watch?v=5lMJS7Loknk

Mine indexed properly after the FW flash, but was off center so had uneven vignetting. Qhy wheel is garbage IMO. Build quality and software...

*After the update, it has been working flawlessly for me.
The uneven vignetting was an issue for me as well before the update.

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The Miserable State of Opto-Mechanical Design in the World of Amateur Astronomy Gear Generic equipment discussions · John Hayes · ... · 37 · 3129 · 13

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