Where do you get hocus focus? I cant seem to find it anywhere.
Also, what about the tilt plate on the QHY268M and 600M?
Qhy doesn't have a tilt plate. They use the word tilt but they really are saying rotator.
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Where do you get hocus focus? I cant seem to find it anywhere.
Also, what about the tilt plate on the QHY268M and 600M?
Qhy doesn't have a tilt plate. They use the word tilt but they really are saying rotator.
The 268M does have a tilt plate as does the 600 Ultra Short BF version.
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Where do you get hocus focus? I cant seem to find it anywhere.
Also, what about the tilt plate on the QHY268M and 600M?
Qhy doesn't have a tilt plate. They use the word tilt but they really are saying rotator.
The 268M does have a tilt plate as does the 600 Ultra Short BF version.
Thanks Bill. I have a 268m, so I should have known that. I guess I completely ignored this feature, as it has little practical use and value. To Eteocles: It's not worth using. Just as crude as the ZWO. If thats all you have then give it a try, but if you have a tilt issue and you really want to dial it in you need something more precise.
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Where do you get hocus focus? I cant seem to find it anywhere.
Also, what about the tilt plate on the QHY268M and 600M?
Qhy doesn't have a tilt plate. They use the word tilt but they really are saying rotator.
The 268M does have a tilt plate as does the 600 Ultra Short BF version.
Thanks Bill. I have a 268m, so I should have known that. I guess I completely ignored this feature, as it has little practical use and value. To Eteocles: It's not worth using. Just as crude as the ZWO. If thats all you have then give it a try, but if you have a tilt issue and you really want to dial it in you need something more precise.
I see what you mean. I think my tilt is coming from my blue fireball rotator, which is unfortunate because that’s my only way of rotating my Epsilon. The Baader tilter would put me a little over the back focus if I keep the rotator.
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Jure:
Where do you get hocus focus? I cant seem to find it anywhere.
Also, what about the tilt plate on the QHY268M and 600M?
Hocus Focus is a plugin for N.I.N.A. Web site
Thanks, I do use NINA but I had to update to the latest version to see Hocus Focus.
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My journey with the Octopi is interesting to me. I’ve had an Octopi with an ASI6200MC on my RASA 11 for about a year. I’ve owned the RASA and that camera for two years. It’s a wonderful device once you understand exactly how to use it.
I did not use ASTAP or CCD Inspector manually to measure tilt. As described in this post, I went the Hocus Focus/NINA route. At the beginning of the process my adjustment recommendations were +/-125 microns on top left and bottom right, and +/-25 microns top right and bottom left. After making small adjustments over about 3 hours I was within 3-5 microns of error on each corner. My stars looked great, but this was not the end of the story.
I was ecstatic that my images were so improved and it was noticeable, in fact obvious. I’d been planning on imaging the Witch Head, so I polar aligned, recalibrated guiding, and setup an advanced sequence in NINA. Once the first images starting coming in, again I was amazed at how great the stars were along the edges. But something was wrong.
I noticed all the images had a “rainbow arc” glare along some of the edges. 🤯 After some lengthy research on this issue I learned that the Octopi exacerbates an issue that is prevalent with RASAs. The starlight along the edges of the sensor is now so precisely focused it reflects/bounces off the metal surfaces in the lens group.
No, it’s not an Octopi problem, it is a RASA problem, but most RASAs’ camera tilt is so bad that the “rainbow arcs” aren’t noticeable since the tilt is so far off. Some flocking paper appears to be the solution, and if you’re interested in knowing more there is a thread on cloudynights about RASAs and rainbow arcs.
I love the Octopi and I’m happy to learn how to resolve issues, but it has been a challenging process to identify the issues and implement the solutions.
Clear minds and clear skies my friends.
jason
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Slightly tangential but I thought that this discussion on Cloudy nights was interesting wrt possibility of software solutions to analysing and then ameliorating the effect of field distortions on images.
https://www.cloudynights.com/topic/833903-software-for-curvaturecoma-correction/
I think that the gist of it is that yes it could be done to restore star shapes but that such a fix could only be cosmetic in nature and create artifacts. So no escape from having to fix tilt and coma etc in reality.
Tim
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Linwood Ferguson:
Got it. Makes sense. Thanks everyone.
Any thoughts on how one decides if the cage or octopi is a better choice?
Aside: I'm asking in anticipation that I have to re-do tilt when i change OTA's, and so while I can do it with the ASI tilter, I would assume these make it much easier and thus quicker.
___
I've not used the cage. I helped beta the Octopi so I prefer it as he made a major update for the 2nd one with my suggestions. I wanted to remove the connection ring issues on my RASA's. The Octopi comes with it's own dove tail connector which replaces the original (poor design).
I like that the cage is "open" as in you can see the front of the camera. This allows you to measure with calipers roughly to get started. I just went through this with the new Octopi and mount and I really didn't know what distance my camera was starting at. So there was a lot of guessing. I finally did find it and while Hocus Focus looked best, IT DIDNT WORK RIGHT FOR ME. I used CCDI and then ASTAP to confirm CCDI results and both were very close to same. I then ran Hocus Focus and it gave horrible results. Yet stars look fantastic. I don't know whats wrong with H-F.
Anyway - ended here with Octipi on Rasa 11. F2.2 is a killer. No room for error.
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Ron Kramer:
o there was a lot of guessing. I finally did find it and while Hocus Focus looked best, IT DIDNT WORK RIGHT FOR ME. I used CCDI and then ASTAP to confirm CCDI results and both were very close to same. I then ran Hocus Focus and it gave horrible results. Yet stars look fantastic. I don't know whats wrong with H-F.
Ron,
I posted about this a few pages back. In a nut shell, Hocus Focus and ASTAP will both struggle to get you to perfection. They will get you really close, but thats as far as they can go. ASTAP (focus bracket analysis) is a little better than Hocus Focus, but again, not perfect. I think HFD and FWHM are a little more robust than HFR (Which HF uses) but all can be confused by aberrated stars that exhibit eccentricity or astigmatism. The theory is that a tilted sensor will show simple defocus off-axis which would result in simply a larger star. If that were the case, both programs would get you to perfection. The reality is, defocus is COMBINED with an effect of field curvature. So stars are not round... The analysis falls short.
With my GTX and an APS-C sensor, NINA/ASTAP are perfect. But that system has a very flat field across an APS-C size chip. With full frame... no bueno. You must dial in the final tweaks visually.
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Daniel Carter:
Sorry I was a bit vague on the description. As Bill mentioned, you remove the tilt adapter from the 6200 and then slide it into the cage and it is secured via a clamping mechanism. The Photon Cage now has a female M54 thread which connects to your EFW. You would need a male to male M54 adapter to attach the Photon Cage to the EFW.
The ZWO tilt plate needs to be removed for either the Photon Cage or Octopi.
If using the Octopi, it is the same method, remove the tilt plate and it slides into the Octopi and it is secured. The Octopi can be attached directly to your EFW with screws (at least it could with my Pegasus Indigo - I think it is the same for other brands but I cannot confirm).
So on the Cage, it takes a male-to-male adapter, which are often less than secure. Do you find it attaches securely to the EFW, doesn't shift or titl or anything? Is the back of the cage completely flush against the EFW? I think I have some male-male that are zero length, i.e. no shoulder. Or does it require one with a shoulder, which would leave a gap between EFW and Cage?
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Linwood Ferguson:
Daniel Carter:
Sorry I was a bit vague on the description. As Bill mentioned, you remove the tilt adapter from the 6200 and then slide it into the cage and it is secured via a clamping mechanism. The Photon Cage now has a female M54 thread which connects to your EFW. You would need a male to male M54 adapter to attach the Photon Cage to the EFW.
The ZWO tilt plate needs to be removed for either the Photon Cage or Octopi.
If using the Octopi, it is the same method, remove the tilt plate and it slides into the Octopi and it is secured. The Octopi can be attached directly to your EFW with screws (at least it could with my Pegasus Indigo - I think it is the same for other brands but I cannot confirm).
So on the Cage, it takes a male-to-male adapter, which are often less than secure. Do you find it attaches securely to the EFW, doesn't shift or titl or anything? Is the back of the cage completely flush against the EFW? I think I have some male-male that are zero length, i.e. no shoulder. Or does it require one with a shoulder, which would leave a gap between EFW and Cage?
Not sure if it was in this thread or the e160 thread, but Bill ordered his cage with a male thread on it.
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Linwood Ferguson:
Daniel Carter:
Sorry I was a bit vague on the description. As Bill mentioned, you remove the tilt adapter from the 6200 and then slide it into the cage and it is secured via a clamping mechanism. The Photon Cage now has a female M54 thread which connects to your EFW. You would need a male to male M54 adapter to attach the Photon Cage to the EFW.
The ZWO tilt plate needs to be removed for either the Photon Cage or Octopi.
If using the Octopi, it is the same method, remove the tilt plate and it slides into the Octopi and it is secured. The Octopi can be attached directly to your EFW with screws (at least it could with my Pegasus Indigo - I think it is the same for other brands but I cannot confirm).
So on the Cage, it takes a male-to-male adapter, which are often less than secure. Do you find it attaches securely to the EFW, doesn't shift or titl or anything? Is the back of the cage completely flush against the EFW? I think I have some male-male that are zero length, i.e. no shoulder. Or does it require one with a shoulder, which would leave a gap between EFW and Cage?
Not sure if it was in this thread or the e160 thread, but Bill ordered his cage with a male thread on it.
Yes, I asked Josh on Facebook if he could make mine with a male M54 instead. If you reach out they may do the same. They are also working on a modular bottom plate that will allow changing the thread interface and a bolt to wheel option.
The vendor was great to work with and the product is very solid and well engineered.
Bill
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The vendor was great to work with and the product is very solid and well engineered.
Amen to that. I exchanged a lot of mails with Josh and he was very forthcoming, gave me some great advice, answered all my questions and then some. One small detail that I find really helpful: both rings have icons and labels so you always know what is what. It happened more than once that I had an Allen wrench already inserted and then I noticed the word "Backfocus" next to it! Oops, wrong screw!
My version has a female thread on the Cage and the EFW has a female thread as well. The M54 to M42 adapter has a 2mm shoulder - similar to the one I used before to connect ASI2600 with the original tilt plate to the ZWO EFW (old version). So far, I had no problems, the connection seems quite solid.
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Very interesting reading. My Stellarvue + the ASI6200 still seems fine some now many months after flattening with NINA. I do not breathe on the system, but if I have to flatten again looks like the Octopus is winning the horse race?
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Very interesting reading. My Stellarvue + the ASI6200 still seems fine some now many months after flattening with NINA. I do not breathe on the system, but if I have to flatten again looks like the Octopus is winning the horse race?
I've been trying to figure that out. Octopi has been around longer, has lots of happy users. Cage has (so far as I can tell) all happy users as well, just fewer. I have heard a few Octopi users comment on a learning curve and poor documentation, but good support when that leads to questions.
In terms of features, the clear separation of function of backfocus and tilt on Cage seems significant (and better).
Conversely, for the ZWO EFW, I think (emphasis on think) the Octopi screws-to like on a camera, but the Cage appears to rely on a male-to-male threaded adapter. My plan is to reach out to the cage vendor for clarity and alternatives, that just doesn't sound (sight unseen, just speculating) a great way to connect.
I am curious if people see other distinguishing features.
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This has been a fantastic thread, and I appreciate all the info and comments. I am tackling tilt for my first time ever, on a ZWO2600MM pro. In my case, I have it screwed directly into the EFW (removed that ZWO tilt plate), as I wanted to see what results I got without it there at all....(as it seemed pretty impractical to use that tilt plate in the first place, as making adjustments would require basically taking the thing apart, tweak the screws, put it back together, take shots, rinse and repeat, etc). Anyway, to be fair, I had not seen this thread yet, so I did not use any sort of focus routine on either side of focus....I just did a normal night of LRGB shooting, and checked all those subs in ASTAP. What I found amazing was that with certain filters, I had no tilt whatsoever....and with other filters, same shooting night and session, just minutes apart, I would see "extreme" tilt as measured by ASTAP. I do have the EAF set to do an autofocus run when filters change, so it did go for optimal focus (rather than the main method here of purposely going in and out of focus)....but those results really confused me that I could have no tilt on some filters and extreme with others. I shot a second night and the same thing happened again, only with different filters that night. Does this make logical sense that this could be the case, maybe based on different focus positions that the EAF arrived at before starting its sequence? I realize these are individual subs (between 3 to 5 mins) and using them as a guide is not the best thing, if I don't know what I am looking forbut....I was just very surprised to see such varied ASTAP measurements on subs taken on the same night.....or with the same set up across multiple nights. As it showed me that just using individual subs and then measuring them would be a really tricky process! The results were just all over the place.....
The second thing I was curious about is....once u do make the needed adjustments and figure out the right tilt settings, I am assuming then u basically have to "lock down" that imaging train, and maybe try to avoid breaking it down, setting it back up, moving the camera to different rigs, etc? I have three different scopes....and have been trying to use the same camera across all 3. But since I don't know WHERE I am getting tilt in each of these set ups, I feel like if I fix it for one scope and configuration, it might be making it worse on another? Depending on where the tilt is coming from. Unless the tilt was just from the sensor, in which case, I guess it would apply no matter the scope and set up?
Really appreciate this thread, it has been great to learn all about these topics!!!
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Tom Bock:
What I found amazing was that with certain filters, I had no tilt whatsoever....and with other filters, same shooting night and session, just minutes apart, I would see "extreme" tilt as measured by ASTAP. I do have the EAF set to do an autofocus run when filters change, so it did go for optimal focus (rather than the main method here of purposely going in and out of focus)....but those results really confused me that I could have no tilt on some filters and extreme with others.
Tom,
Most likely what you are seeing is varying quality of focus. Defocus will amplify the tilt effect as field curvature really starts to play a role. Even though you might be pretty well focused in the center each time, the corners may have a slight defocus. Do a visual inspection of a frame that shows no tilt according to ASTAP and compare it visually to a frame that has extreme tilt. You will probably notice larger FWHM in the corners of the "extreme" tilt image. Probably nothing to worry about. What scope are you using? The EAF has a pretty large step size so depending on the scope it may not be the best match. You might also be able to fine tune your focus routine to achieve a more precise and accurate focus.
As to your second question: You may or may not need to fix tilt when you change your camera to a new scope. It really depends on a lot of things, including how OCD you want to be about this. I have two scopes and two cameras, and I dont change cameras around between scopes... I'm a little crazy about star shape....
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Tom Bock:
The second thing I was curious about is....once u do make the needed adjustments and figure out the right tilt settings, I am assuming then u basically have to "lock down" that imaging train, and maybe try to avoid breaking it down, setting it back up, moving the camera to different rigs, etc? I have three different scopes....and have been trying to use the same camera across all 3. But since I don't know WHERE I am getting tilt in each of these set ups, I feel like if I fix it for one scope and configuration, it might be making it worse on another? Depending on where the tilt is coming from. Unless the tilt was just from the sensor, in which case, I guess it would apply no matter the scope and set up?
Indeed. First of all I need to thank Chris for the outstanding writeup. I will be doing another tilt adjustment.
BUT, as Tom noted, I use my ASI2600mm on three different image trains. I'll bet dollars to donuts that once I get it fixed for one system, the others will suffer. Case in point. I had already struggled with the ZWO tilt adjustor (where you need to disassemble and reassemble after each test) and got my GT102 and ASI2600 working really well. A few nights ago I moved the camera (and FW) to my ZS61. Corners on the right side of the frame show terrible stars. SO, I bet if I spend the time to fix it, when I return the camera to the GT102 I'll end up with problems there once again. Seems like a futile effort when you have one camera and multiple OTAs.
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Michael J. Mangieri:
Seems like a futile effort when you have one camera and multiple OTAs.
Unfortunately, thats the cost of doing business when using large sensors with 3.76um pixels. These conversations were less frequent and tilt was less of an issue with the more forgiving 5.4um to 9um and larger pixels of yesteryear.
The payoff though is pretty high resolution imaging with shorter focal length scopes, and huge FOV when paired with very short focal length scopes.
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Michael, I'm in the same boat (three OTA's, worse one I will swap a reducer in frequently). My hope though is as I work through them a couple times I will find it repeatable if not identical, so I can know "switching to C11, need 3/4 turn there, 1/3rd there, and 1/8th on that screw" or some such, to at least land close enough. It remains to be seen if that's possible, though I am trying hard to make sure everything involved is big and heavy duty and rigid so there is less variability in assembly.
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Tom Bock:
What I found amazing was that with certain filters, I had no tilt whatsoever....and with other filters, same shooting night and session, just minutes apart, I would see "extreme" tilt as measured by ASTAP. I do have the EAF set to do an autofocus run when filters change, so it did go for optimal focus (rather than the main method here of purposely going in and out of focus)....but those results really confused me that I could have no tilt on some filters and extreme with others.
Tom,
Most likely what you are seeing is varying quality of focus. Defocus will amplify the tilt effect as field curvature really starts to play a role. Even though you might be pretty well focused in the center each time, the corners may have a slight defocus. Do a visual inspection of a frame that shows no tilt according to ASTAP and compare it visually to a frame that has extreme tilt. You will probably notice larger FWHM in the corners of the "extreme" tilt image. Probably nothing to worry about. What scope are you using? The EAF has a pretty large step size so depending on the scope it may not be the best match. You might also be able to fine tune your focus routine to achieve a more precise and accurate focus.
As to your second question: You may or may not need to fix tilt when you change your camera to a new scope. It really depends on a lot of things, including how OCD you want to be about this. I have two scopes and two cameras, and I dont change cameras around between scopes... I'm a little crazy about star shape....
Thanks so much for the response, Chris!!! And I think I am following here ....I most definitely am seeing a larger FWHM in the corners where I am getting the Severe or Extreme tilt readings, even on the same night, just with a different filter. I just went thru sub by sub, and for some reason, my Red filter subs show next to no tilt, and the blue show severe. But in every case, there does seem to be something going on with focus....as the left center is the best (not even the center center), and the right/top right is where all the tilt shows. So it's almost as if there is some tilt here and getting magnified by focus not being crisp across the field. And with the best focus left of center, maybe this pushes the right even further out? These results were on my EdgeHD8. I probably do need to figure out more appropriate EAF settings....
Another observation as I shot with the same ASI2600MM on two scopes ....the EdgeHD, as mentioned above, seems to be inconsistent as far as tilt readings, which might be partly this issue around focus , and focus routine settings sub-optimal....but where the tilt pattern does show, it's ALWAYS in the same side/same corner - upper right to right. Always. I also used the cam on a WO FLT91 refractor, multiple nights, and every sub no matter the filter, ASTAP shows tilt same upper right/right side (just as I see on the Edge ). I would have to assume then that there is SOME tilt going on with that set up for sure, as it's present on every sub. And then with the Edge, maybe not as dramatic, but likely still some tilt..... but exacerbated by the focus issues. Not sure if this is a sound conclusion, but the fact that the tilt, if and when it shows, is ALWAYS on the upper right/right.
Either way, is it safe to assume that the only true way to understand what is going on, is to run Hocus Focus? rather than what I am doing which is just looking at subs after the fact and having to juggle these multiple variables on focus and how it's affecting the tilt......
One other oddity - and this might just be my lack of understanding of how the APS-C sensor re-orients itself after a meridian flip. I also noticed something that threw me......when I saw the tilt in the upper right, consistently, after the meridian flip, in my head I would expect that the tilt would now "move" to the lower left, since the frame/sensor itself flips and re-orients, and those are the same actual corners. However, that is NOT what I saw....the tilt remained in the upper right both before as well as after the meridian flip. I am straining my logic here on why that would be? As maybe the corners do stay the same after the flip....so it does not move upper right to lower left, it stays upper right. Hmmmm.
Again, I can't thank you enough for taking the time to respond to me here. It's a massive help and I sincerely appreciate!
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If you look at uncalibrated frames the image should be flipped 180 degrees after the meridian flip, so the bottom of the sensor is on the bottom of the screen, and does not follow the image.
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Tom Bock:
Tom Bock:
What I found amazing was that with certain filters, I had no tilt whatsoever....and with other filters, same shooting night and session, just minutes apart, I would see "extreme" tilt as measured by ASTAP. I do have the EAF set to do an autofocus run when filters change, so it did go for optimal focus (rather than the main method here of purposely going in and out of focus)....but those results really confused me that I could have no tilt on some filters and extreme with others.
Tom,
Most likely what you are seeing is varying quality of focus. Defocus will amplify the tilt effect as field curvature really starts to play a role. Even though you might be pretty well focused in the center each time, the corners may have a slight defocus. Do a visual inspection of a frame that shows no tilt according to ASTAP and compare it visually to a frame that has extreme tilt. You will probably notice larger FWHM in the corners of the "extreme" tilt image. Probably nothing to worry about. What scope are you using? The EAF has a pretty large step size so depending on the scope it may not be the best match. You might also be able to fine tune your focus routine to achieve a more precise and accurate focus.
As to your second question: You may or may not need to fix tilt when you change your camera to a new scope. It really depends on a lot of things, including how OCD you want to be about this. I have two scopes and two cameras, and I dont change cameras around between scopes... I'm a little crazy about star shape....
Thanks so much for the response, Chris!!! And I think I am following here ....I most definitely am seeing a larger FWHM in the corners where I am getting the Severe or Extreme tilt readings, even on the same night, just with a different filter. I just went thru sub by sub, and for some reason, my Red filter subs show next to no tilt, and the blue show severe. But in every case, there does seem to be something going on with focus....as the left center is the best (not even the center center), and the right/top right is where all the tilt shows. So it's almost as if there is some tilt here and getting magnified by focus not being crisp across the field. And with the best focus left of center, maybe this pushes the right even further out? These results were on my EdgeHD8. I probably do need to figure out more appropriate EAF settings....
Another observation as I shot with the same ASI2600MM on two scopes ....the EdgeHD, as mentioned above, seems to be inconsistent as far as tilt readings, which might be partly this issue around focus , and focus routine settings sub-optimal....but where the tilt pattern does show, it's ALWAYS in the same side/same corner - upper right to right. Always. I also used the cam on a WO FLT91 refractor, multiple nights, and every sub no matter the filter, ASTAP shows tilt same upper right/right side (just as I see on the Edge ). I would have to assume then that there is SOME tilt going on with that set up for sure, as it's present on every sub. And then with the Edge, maybe not as dramatic, but likely still some tilt..... but exacerbated by the focus issues. Not sure if this is a sound conclusion, but the fact that the tilt, if and when it shows, is ALWAYS on the upper right/right.
Either way, is it safe to assume that the only true way to understand what is going on, is to run Hocus Focus? rather than what I am doing which is just looking at subs after the fact and having to juggle these multiple variables on focus and how it's affecting the tilt......
One other oddity - and this might just be my lack of understanding of how the APS-C sensor re-orients itself after a meridian flip. I also noticed something that threw me......when I saw the tilt in the upper right, consistently, after the meridian flip, in my head I would expect that the tilt would now "move" to the lower left, since the frame/sensor itself flips and re-orients, and those are the same actual corners. However, that is NOT what I saw....the tilt remained in the upper right both before as well as after the meridian flip. I am straining my logic here on why that would be? As maybe the corners do stay the same after the flip....so it does not move upper right to lower left, it stays upper right. Hmmmm.
Again, I can't thank you enough for taking the time to respond to me here. It's a massive help and I sincerely appreciate!
Tom,
I assume you are using a full field focus routine? Where all the stars in a field are analyzed and plotted on a curve with vertex of the curve being the chosen focus point? This can be problematic with very long focal length scopes. You might only have a few stars in the frame that are being analyzed and as you defocus even fewer yet. I have seen a focus routine literally only using 2 or 3 stars with an EDGE scope. It does not give you a very robust focus model, especially if the stars it is selecting are all on one side of the frame. get what I'm saying? I only use a single star focus method now, but not all software will support this. Take a look next time you run AF. The program should tell you how many stars are being analyzed for the routine, and maybe even where they are. You might have too large of focuser jumps between samples, and your exposure length might be too short to resolve enough stars. Take a look at your settings and see what you can tweak. You need to get consistent results in order to have anything meaningful when it comes to understanding tilt.
Run the Hocus Focus test. A full focus bracket analysis can give you better insight as to what your have for tilt.
As to your second question, Linwood explained. Just because you have a meridian flip, the tilt is still in the same place in your image train. So if you have bad stars in the upper left, then do a meridian flip... you still should have bad stars in the upper left. It will only swap corners after you register your subs.
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Thank you so much for this article. Very helpful. I have seen "almost none" tilt, however I do see backspacing issues and I rely on guesswork. With hocus focus I guess I can take out the guesswork!
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Tom Bock:
Tom Bock:
What I found amazing was that with certain filters, I had no tilt whatsoever....and with other filters, same shooting night and session, just minutes apart, I would see "extreme" tilt as measured by ASTAP. I do have the EAF set to do an autofocus run when filters change, so it did go for optimal focus (rather than the main method here of purposely going in and out of focus)....but those results really confused me that I could have no tilt on some filters and extreme with others.
Tom,
Most likely what you are seeing is varying quality of focus. Defocus will amplify the tilt effect as field curvature really starts to play a role. Even though you might be pretty well focused in the center each time, the corners may have a slight defocus. Do a visual inspection of a frame that shows no tilt according to ASTAP and compare it visually to a frame that has extreme tilt. You will probably notice larger FWHM in the corners of the "extreme" tilt image. Probably nothing to worry about. What scope are you using? The EAF has a pretty large step size so depending on the scope it may not be the best match. You might also be able to fine tune your focus routine to achieve a more precise and accurate focus.
As to your second question: You may or may not need to fix tilt when you change your camera to a new scope. It really depends on a lot of things, including how OCD you want to be about this. I have two scopes and two cameras, and I dont change cameras around between scopes... I'm a little crazy about star shape....
Thanks so much for the response, Chris!!! And I think I am following here ....I most definitely am seeing a larger FWHM in the corners where I am getting the Severe or Extreme tilt readings, even on the same night, just with a different filter. I just went thru sub by sub, and for some reason, my Red filter subs show next to no tilt, and the blue show severe. But in every case, there does seem to be something going on with focus....as the left center is the best (not even the center center), and the right/top right is where all the tilt shows. So it's almost as if there is some tilt here and getting magnified by focus not being crisp across the field. And with the best focus left of center, maybe this pushes the right even further out? These results were on my EdgeHD8. I probably do need to figure out more appropriate EAF settings....
Another observation as I shot with the same ASI2600MM on two scopes ....the EdgeHD, as mentioned above, seems to be inconsistent as far as tilt readings, which might be partly this issue around focus , and focus routine settings sub-optimal....but where the tilt pattern does show, it's ALWAYS in the same side/same corner - upper right to right. Always. I also used the cam on a WO FLT91 refractor, multiple nights, and every sub no matter the filter, ASTAP shows tilt same upper right/right side (just as I see on the Edge ). I would have to assume then that there is SOME tilt going on with that set up for sure, as it's present on every sub. And then with the Edge, maybe not as dramatic, but likely still some tilt..... but exacerbated by the focus issues. Not sure if this is a sound conclusion, but the fact that the tilt, if and when it shows, is ALWAYS on the upper right/right.
Either way, is it safe to assume that the only true way to understand what is going on, is to run Hocus Focus? rather than what I am doing which is just looking at subs after the fact and having to juggle these multiple variables on focus and how it's affecting the tilt......
One other oddity - and this might just be my lack of understanding of how the APS-C sensor re-orients itself after a meridian flip. I also noticed something that threw me......when I saw the tilt in the upper right, consistently, after the meridian flip, in my head I would expect that the tilt would now "move" to the lower left, since the frame/sensor itself flips and re-orients, and those are the same actual corners. However, that is NOT what I saw....the tilt remained in the upper right both before as well as after the meridian flip. I am straining my logic here on why that would be? As maybe the corners do stay the same after the flip....so it does not move upper right to lower left, it stays upper right. Hmmmm.
Again, I can't thank you enough for taking the time to respond to me here. It's a massive help and I sincerely appreciate!
Tom,
I assume you are using a full field focus routine? Where all the stars in a field are analyzed and plotted on a curve with vertex of the curve being the chosen focus point? This can be problematic with very long focal length scopes. You might only have a few stars in the frame that are being analyzed and as you defocus even fewer yet. I have seen a focus routine literally only using 2 or 3 stars with an EDGE scope. It does not give you a very robust focus model, especially if the stars it is selecting are all on one side of the frame. get what I'm saying? I only use a single star focus method now, but not all software will support this. Take a look next time you run AF. The program should tell you how many stars are being analyzed for the routine, and maybe even where they are. You might have too large of focuser jumps between samples, and your exposure length might be too short to resolve enough stars. Take a look at your settings and see what you can tweak. You need to get consistent results in order to have anything meaningful when it comes to understanding tilt.
Run the Hocus Focus test. A full focus bracket analysis can give you better insight as to what your have for tilt.
As to your second question, Linwood explained. Just because you have a meridian flip, the tilt is still in the same place in your image train. So if you have bad stars in the upper left, then do a meridian flip... you still should have bad stars in the upper left. It will only swap corners after you register your subs.
**yes, I am running the full field focus routine, and do so initially and upon all filter changes. Definitely sounds like I need to make a few tweaks here beyond just the long exposure times that I have set on some of my darker filters when using the EAF on the Edge. I will definitely look into that. And more importantly, run Hocus Focus and probably easier to do so on my FLT91 refractor. As that is most definitely where I see more consistent tilt, and mostly the focus routine will run far better there at such a reduced focal length than the Edge. This thread overall has been great and I appreciate all the responses! Looking forward to making some progress here once I can get a clear night (which might be a while here in the PacNW!! 😂)
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