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Ron Kramer: I want to chime in here and give perspective on the product we produce before any of this gets out of hand and defamatory. The Photon Cage was not made just for a RASA 11, but rather any scope and any camera combo and as a modular device with functionality we could not find in any other device. We did our research, we looked at about half a dozen tilt devices on the market, even historical devices, and we did ask questions about them to see if they offered such functionality that we needed, and none offered it… so this was produced. The idea that we raped and pillaged or stole ideas is a bit offensive and vastly untrue. I set out to create a device for my RASA 8 and then make it portable and modular so I could move to the RASA 11 or an SCT in my case without the need to buy another device. My RASA 8 requirements were:
On a RASA 11, I don’t want to change out my optical system or touch the stock optical system on the scope. And the picture is using a custom M54 adapter I made and sell, not the M48 or M42 stock camera holders with felt. I like it this way, metal on metal, but if you want to use another method or feel it’s flawed, so be it. I personally don’t mind the stock mount so I made mine without felt and it works very well for me this way. I don’t move my system laterally for my own specific reasons. There was never intention to copy anything. Obviously, we’re mounting a camera to a telescope so we’re working with round to round fitment. The cage was a product of what I needed along with research of what others didn’t offer or fell short of. |
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Ron Kramer: The Hocus-Focus 3D view of your surface appears strongly tilted and curved, but that is simply because it has been scaled to fit in the 3D box of the graph. If you look at the actual tilt and curvature values, the tilt is 0.08 degrees and the curvature is almost 8 meters - with a good fit of the data to the model. So it isn't saying it is grossly out of whack - it is an actual measurement of the image surface and the results are not inconsistent with the other images you show. The main difference is that the H-F result is a true measure of tilt and curvature of the image surface rather than a likely misleading guess based on a single image. I had seen your earlier images from weeks ago showing a diagonal band of stars across the image - and in that case the H-F plug in was saying you had a tilt of about 1 degree - and that was likely the case based on the images. So it appears to have always been telling you exactly what the problem was with the setup - whether it was large tilt of a degree, or a very small amount as you see now. It's possible you could improve things slightly, but you might first want to do multiple runs to confirm the result is repeatable. If the amount of tilt is small enough that it is in the noise of normal shifting and flexure of the system then it may not be worth adjusting. I don't know why you have trouble with the routine timing out - but I'd encourage providing feedback on the issue so it gets resolved. Frank |
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Bill Long, what telescope are you using the photon cage with? Thanks - Dave Bill, I'm going for the same setup (130GTX, flattener, photon cage), but with a QHY600 and using the Indigo FW. I know you also have a QHY600, so I'm just wondering if you've ever tried it on the 130GTX with the photon cage, or is it now permanently attached to your Epsilon? Thanks |
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Bill Long, what telescope are you using the photon cage with? Thanks - Dave I have not tried the cage with the 600. That's basically permanently attached to my Epsilon with the Octopi. |
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| Thank you Chris for your =HwtZe=jCAhz ChMk0b=ryNqvbprecise and objective description. Just a clarification i ask you: by backspacing do you mean the distance between the mirrors and therefore the relative backfocus at the exit of the telescope or the distance between the reducer and the sensor? |
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Fabio Guerceri: Backfocus/backspacing in this discussion refers to the distance between the camera sensor and the corrective optics (field flattener/reducer/coma corrector) |
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I tried reading through this whole thread and may have missed it but.... I have three OTA's, two of which have reducers, so five possible combinations. While i have not tried like for like in more than 3, I get significantly different tilt results on each, not just magnitude but direction. I suspect the imaging train and/or just plain optics are at fault, and I further suspect there is no simple fix (like tightening the focuser). I assume I'm not the only one who moves a camera between OTA's. How are you handling that? Do you put one tilt device on the camera, adjust it on the setup you think most square, then put a separate in-line tilter on the rest to fine tune them? Or re-do tilt every time you change? (I may have to shoot myself if that is your answer, or stop changing OTA's). Here is an example before I started changing anything, everything just flat. Left is a C11, middle a SVX152T with SFFX-2, right is a NP101is. I've since used a QuadTCC on the SVX152T and spent many hours working on tilt and backfocus; I might hope if I move it now to the others it magically is perfect, but I suspect in fixing one setup I will have made some worse and some better. Or because Murphy hates me, maybe all worse. So... if you move trains between OTA, how do you deal with it? Linwood PS. For consistency and rigidity, I converted everything to M68 between flattener and camera, so movement is to unscrew the train after the setup specific spacers (for backfocus), and move it (OAG, EFW, ASI6400MM) to the other setups. Fastest setup is F5.4, slowest F10, so I'm not dealing with the super fast RASA issues (my blood pressure would not handle it well).  |
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Linwood Ferguson: So just to throw my two cents in here on this... I personally think you will or need to redo tilt and all this specific to each scope and setup. I know most telescope manufacturers give recommended backfocus and many use tools to get precisely there, but they often also say that is +-1mm or some other value depending on your scope. Same with cameras, they may say 12.5 or 17.5mm backfocus, but it also will state elsewhere +- .5mm, so to me it's always a process to fine tune it into your application. A good example might be a RASA which specifies something like 72.8mm backfocus recommended, but they also say that is +- 1mm, then QHY also says their camera can be +- .5mm and then there are filter differences and machining differences in everyone's equipment, then you consider just the threading of your optical train on to one scope and then the next... it can tilt things and be slightly different or not bed into one thread turn and your backfocus is different. For this reason, I leave my camera on the same scope, even rotation and orientation for a few weeks. If I touch mine or rotate it, I redo tilt. Now the good news really is the new software out there that can make it quick, and I redo mine in about 15 minutes... then I'm good for a few weeks. Again, just my thought as to why different results here. Love to hear what others recommend. |
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Josh Jones: For clarity, I expect to have to do separate backfocus for each scenario, and indeed have done so. Each one has a separate set of spacers (that stay with the OTA) so that when I add the camera train they are at the right, already fine-tuned backfocus. That part is easy, at least relatively so. It is also pretty quick to do. But tilt is more complicated. It's the thing that takes hours and dozens of trips inside and out to make adjustments. It is not attractive to do that every time I change OTA's, or add a reducer. I was hoping people had worked that out. For example, if I had a back end tilter (e.g. the photon cage or octopi) and a front side tilter (e.g. Baader makes one that is fairly thin) can I match the camera to one OTA (let's say without the front side) and on the other three use the front side to match tilt, and expect when I go between OTA's it will stick? Or are people finding you just can't disassemble and reassemble an imaging train and end up with the same tilt, it has to be redone just from the act of dis/re-assembly? |
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Linwood Ferguson: Linwood, You cant easily compare one setup tilt map to another setup tilt map. The single frame is only useful when comparing results before and after adjustment on the SAME setup. The problem is that there is just too many variables that go into this analysis. Field curvature compounds tilt so if you have one setup that is very flat and one that has a little field curvature, the latter might look horrible on a tilt map. Also if you have one setup that shows astigmatism and another that doesnt you cant really compare tilt maps because astigmatism is confusing for HFD and HFR analysis. I'm going to all caps the next thing because its really important... and I'm not really shouting. WHAT REALLY MATTERS IS HOW THE STARS LOOK. Do they look round to your expectation or do they have issues when you move one setup to the next? How much of a real impact is this in the first place? A tilt device placed at the camera like Octopi or photon cage, can only square the camera with the rest of the image train. A tilt device like the Gerd placed between your image train and the flattener will square your entire image train to the OTA. If you are going to swap setups frequently, you might have better luck with a tilt solution that encompasses as much of the image train as possible. That way all the bits and pieces are square to the OTA interface. This assumes your optics are well collimated and there is not focuser tilt. This is theory though, and reality tends to stray. I use the octopi and the level of precision over the Gerd is well worth it in my opinion... but I'm a little OCD about my stars. I dont face the same issue that you do though. I have two scopes and two cameras and I leave them alone... no switching around gear. I have no problems rotating though. My equipment is very precise though. On the GTX I rotate the doveloc, which is perfect and does not introduce tilt. When I rotate on the Epsilon I rotate the upper flange of the LEO, which is also very precise and does not introduce tilt. YMMV. Unfortunately, if you want to use cameras that have large chips and tiny pixels you will need to dial in tilt when you change from one scope to another. Once you have done this a few times though, dialing things in isnt that bad. With my GTX I can dial in tilt in about half an hour or less. With the epsilon it can take a couple of sessions, but I can get pretty close pretty quick. Don't shoot yourself... just buy another camera. |
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Linwood Ferguson:Josh Jones: Maybe you could setup a camera tilt device and then have a separate tilt device for every scope... but eek. That makes my head spin and I understand this stuff pretty well having spent so much time exploring the topic. The Baader is a pretty crude device (less precise than the Gerd) but most infuriating is that they put M68 male on once side and M68 female on the other so its really a PIA to adapt to any other size thread. They should have put female on both sides so you could easily adapt to a smaller thread size without losing a ton of backspacing. In any event, I dont think this would be a fun process. I'm sure it could be done, but keep in mind that we are dealing with micron level adjustments here due to the compounding nature of field curvature and tilt. |
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@Chris white thanks. Won't quote everything but a couple points and replies: In terms of how stars look is a bit of a story. The C11 without the reducer I think is just fine, probably because of the F10 depth of focus range. The NP101is is pretty poor in the corners, talking to TV they said more or less "wasn't designed for these tiny pixels". The SVX152T I am being proactive, I know it has a lot more potential than the others, so am trying to get it dialed in carefully. Also, the QuadTCC on it looks pretty bad if it is just slightly off in either backfocus or tilt (it looks pretty good as I get close). So... mixed bag. I expect the C11 and SVX152T to be the most repeatable in terms of OTA and focuser, because they have moonlites. The NP101is has a dovetail rotator and a (relatively speaking) light duty focuser. My GUESS is that it has tilt that changes every time I rotate. It has a built in tilter but I had zero luck with it, very hard to change, very hard to control the change. Sadly it has no room for any other tilter in my train. So primarily I am working on the new SVX152T with the QuadTCC, then see how it looks with the Flattener (expecting it to be less sensitive) and hope they end up the same (in terms of tilt). If not, I do have room for the baader tilter, though I think not the Gerd. Then hope the C11 is OK, and maybe write off the NP101is if it's showing tilt. Or adjust each time. But I was hoping others had some great magic idea. |
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Linwood Ferguson: Magic? Dialing tilt out of a large sensor with 3.76um pixels? Microns man...  |
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Linwood Ferguson: You just have to believe... believe... believe... Piezo actuators and a driver so you just tell NINA to "tune it" and come back in an hour while I take a nap.  |
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I finally had the chance to use the Photon Cage under the stars on my 106mm F/4.95 APO. It took me a couple of nights to get HF producing at least reasonably accurate focus (within my 61microns CFZ). I am not sure why I have such difficulties with HF, NINA nails focus perfectly. Using ZWO EAF, I am. To add another variable to the equation, my old EQ-6 started spiking in DEC. Irregular, out of the blue, quite bad - and nothing I do will cure it (luckily, I have another mount coming very soon!) So, after losing 5 hours to HF issues and another to realize that I was not getting consistent results from the HF Aberration Inspector I managed to get close to getting rid of tilt. Not quite, but close. Before:  After:  Lessons learned? - Hocus Focus must produce good, consistent results every single time - run HF AI high up in the sky, preferably near zenith with good seeing. Or else every single run will differ from the previous - need good mount tracking! My DEC spikes threw HF AI off it's tracks. - SMALL adjustments on the tilt device! One corner at a time! I tried adjusting all four at once and had to start from scratch The most reliable component in this story was the Photon Cage. It took a few cautious tries in the beginning but I soon got the feel just how much I need to turn which screw. With fours screws, one for each corner id doesn't get any easier than this. Mechanically it is very sturdy, there is no play or sag anywhere. I even removed the camera from the Cage after adjusting tilt, then reinserted it and there was literally no difference. I am done for the moment. Once I get my new mount I am confident I can improve further, but as it is, the old EQ-6 is just too unpredictable. On the other front, if anybody has some advice about how to tame Hocus Focus, I'd really be grateful! I tried everything.... by the way, my focuser step size is 4.66 microns, with only 3 steps in HF, step size of 45 and Overshoot backlash at OUT=100 I managed to at least get within the CFZ. But the hyperbola is anything but that! Jure Edit: my camera is ZWO ASI2600MM Pro |
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Has anyone tried both the photon cage and the octopi? Is there a distinguishing feature of either to consider to decide? And does the Photon Cage fit the 6200 as well (I keep reading about the M54 threaded, but the ZWO is a screw-on, not sure of the size). |
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Linwood Ferguson: The Photon Cage will fit the 2600, 2400 and 6200 (the 90mm version). They have another version that fits smaller cameras as well. To connect the Photon Cage to your imaging train requires a M54 male to male adapter (you can find them with as little as 1mm of optical path). The Photon Cage has M54 female threads on the camera side. The Octopi can use screws to attach directly to your EFW if you are using one. I have the Octopi for my Epsilon setup and it screws to my Indigo EFW. I ordered the Photon Cage for my 2600 which I use on most of my refractors and there is a bit of a lead time right now (several weeks). I haven't used the Photon Cage (since I just ordered it) but from my understanding, both correct tilt and backspacing (each in their own way). I think @Bill Long has experience with the Photon Cage now (I think he ordered one and has experience using it now). He also uses the Octopi on his Epsilon rig too. |
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Daniel Carter: The 6200 does not have a threaded adapter on the camera, it has 4 screws. To be more precise, it comes with a tilt adapter which is threaded, but with a EFW and OAG that is removed, the EFW screwed to the camera body, and the tilter put on the OAG. I assume the cage would have to go between the EFW and the camera body, right? are you saying the ZWO tilter has to be reinstalled there to connect to the cage with threads? Actually I'll reach out to the cage vendor and ask... they must have a manual or can explain. |
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You remove the plate, and slide the camera into the cage and secure it. The camera doesn't thread into the cage. You can find YouTube videos on both devices. |
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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). |
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ZWO tilter is removed and the camera slides into the Photon Cage as Bill wrote. It's a snug fit and the two larger horizontal screws are used to lock it in place. To the right is the ZWO tilt plate which I removed. Below the camera in the Cage is the M54 to M42 (T2) which connects the Cage (M54) to ZWO EFW (M42).  My refractor with everything connected. The leftmost ring on the Photon Cage is for adjusting backfocus but so far I had no need for it. It has three screws. The rightmost ring on the Cage is the tilt adjustment ring. First unfasten the large four screws and adjust with the smaller ones. Top side of the camera is where the black "button" is visible just to the left of the rightmost ring. The camera fits only one way, the "button" slides into a recess in the ring so it's perfectly clear which corner is which. |
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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. |
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Linwood Ferguson: The ASI Tilt plate is garbage. Forget using that. I cant recall the thread pitch on those screws but they are very crude and will not give you easier experience you seek. I use the Octopi and I do recommend it. I've seen good reports on the Cage as well. The key is repeatability. If you make good records of positioning and make sure to never change which spacers you use with each setup, you could concievably record how many turns and on which screw you need to adjust between OTA setups. I.E- When going from C11 to 152 you turn the upper right two turns, lower left 11 turn and lower right 1/2 turn, etc... I believe that you could have this kind of precision with the right device. |
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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? |
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Where do you get hocus focus? I cant seem to find it anywhere. Hocus Focus is a plugin for N.I.N.A. Web site |
