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Switching over to a longer focal length setup for galaxy season. Was using a WO GT81 refractor and an imaging train consisting of a WO refractor reducer/ corrector, filter wheel, tilt plate, spacers and a ZWO AS294MC Pro. I used ASTAP to check for tilt. The software revealed 6% tilt which is something but nothing. I moved this "almost" same imaging train but an extra spacer to achieve a 90.3 back focus over to a Celestron C8 and Starizona reducer/corrector. Now ASTAP reveals a 27% tilt. The Starizona piece does not thread on the C8 like the WO piece does to the GT81. It needs a 2" visual back. I bought a Baader Click Lock to make sure of a secure grip and the best centering. I can't understand why there's so much tilt. I can try to get it out by adjusting the tilt plate. It's a ZWO tilt plate which most say are garbage. Is the Starizona Corrector the problem? Any thoughts before I try to adjust it out? This was suggested: Neumann CTU. But I wish I knew which part is the culprit. Mike |
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The biggest source of tilt in any longer focal length, slower systems systems such as a C8 are tilt adjusters. Normal machining tolerances should be sufficient to hold the sensor to within the depth of focus over the entire field. At F/10, the depth of focus is around 250 microns, which is a lot. I’m not familiar with how ASTAP works and you didn’t show any results so I can’t comment on that. Have you used the FWHMEccentricty tool in PI to look at the field? If you measure a dense star field, the FWHM values shouldn’t vary by more than about .5 pixels and the contours of the eccentricity plot should be roughly centered with values less than 0.5. My suggestion is to start by zeroing the tilt on all of your adjusters (or simply removing them) and starting from scratch. I never use tilt adjusters and I’ve never seen tilt on the 4x C14s or on the CDK20 that I’ve used. Unless there is something really screwed up on your C8, it shouldn’t be much different. Just be sure that EVERYTHING is properly seated and pulled tightly together in the image train when you assemble it and you shouldn’t see much sensor tilt. John |
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Thanks John. I have not used the Eccentricity tool in PI. ASTAP is the plate solving software I use with NINA. It has a tool to determine tilt. I can try taking the tilt plate out of the imaging train and substitute it with another spacer. Getting the correct 90.3 distance for back focus on a Starizona corrector is imperative. I just don't understand why the same imaging train I used on the WO worked so well. It included the tilt plate which I have all screws tightened down so the two plates are flush. Can the old C8 I'm using introduce tilt? I would feel better if the Starizona unit was threaded to the back of the C8. But unfortunately, that's not possible. Many people here on Astrobin are or have used the Starizona piece with good success. Mike |
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Mike, Ah...I'm sorry. I am familiar with the NINA image sensor tilt algorithm--and it's pretty good. I agree that getting the back working distance set correctly is critical. There are ways to end up with a tilted image plane with respect to the reference datum on the rear of the telescope but that's only going to happen unless something is seriously out of whack. Just be careful that everything is mounted flush and that nothing wobbles when you firmly grab it and try to move it. Try what I've suggested and if you still can't get it right, let us know and we'll come up with plan B. It might mean that the scope itself has something out of alignment. Speaking of which: Is the scope properly aligned to begin with? I didn't originally take note of the fact that you are using an older, non-Edge system, which means that you'll have both coma and field curvature--most noticeable with a larger sensor. That may be affecting the ASTAP output as well. Having a small misalignment in the secondary will mimic sensor tilt because it will affect the symmetry of the aberration field. So, it's important to start with a very well aligned secondary before you try to evaluate sensor tilt. John |
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I may have two solutions for you, because I'm using also a C8 but not with the Starizona Reducer/Flattner. I'm using the Celestron 0.63x reducer/flatnner. I had also tilt in mine in the beginning, but the problem in my case was the manual rotator from TS Optics. He was the problem in my all systems causing tilt. In your case the problem is probably the way that the Baader Click Lock hold the grip in the piece nosel of the rest of the optical trem. Since the griping is hold in place by centering it with a ring apx. 3-4mm wide, it secures the nosel there, but the weight of the rest of the optical trem is enough to pull to the ground the rest of your capture system, which leads to the tilt. Can you confirm if you are perfectly collimated and also tell me the type of thread in the starizona reducer/flatnner that you have? If you could give the answer to those two question I may help. Clear Skies, Cesar |
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Collation is very close. Although, it wouldn't hurt to check it again. The telescope side of the reducer is a 2" barrel that inserts in the Baader Click Lock. Thr other end is 42mm male threads. Thank you Cesar. I'm going to try something I heard. Turn the scope with the corrector down to the ground. Then insert the imaging train into the click lock and tighten securely. That way the weight of the train is not pulling down at the time of tightening. Just a fancy, maybe? 😜 Mike |
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Mike, so why you just don't acquire a ring reducer from the M48 to the M42? A small one. They usually cheap. You just need to acquire one in order to substitute by the baader click adapter and fill the rest of the imaging train if needed with some M42 rings. If you do that, your changes of catching tilt will be minimal, but as you said, you have a tilt plate on the camera, so you can fine tunning with her after. You only need: - An M48 female to M42 male adapter - M42 extenders (I bought mine in kits) in order to fill the rest of the imaging train up to 90.3mm up to the sensor. Cesar |
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Thank you for the suggestions Cesar. I'll let you know the results. Mike |
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Mike, this is the exemple that I'm talking about: - https://www.highpointscientific.com/william-optics-48mm-female-to-42mm-male-thread-adapter-ye-m48-42 And then you fill the rest of the imaging train with those: - https://www.bresser.de/en/Astronomy/Accessories/Adaptors/BRESSER-T2-Extension-Tube-Set.html Those extension rings kit is in Europe where I'm from, I tried to see if HighPoint Scientific had, but I can't find by that name on a quick search. I pointed HP Scientific, since you're in US, but I know there are others like Agena Astro, OPT, etc. They probably have and you just need to put the Baader click aside. I don't know the connection that you have to the OAG, from the photos that you have in your profile, I'm assuming it's an OAG from celestron, with he as an M42 female thread. You'll have more than enough with those two pieces. If you have the oportunity do like I did: Buy some two or three of those kits. My sugestion like I did. I bough on of those kits of rings for each of my telescopes and I set it up on each for the specific backfocus with acessories. That way I don't need to change and do the math for the backfocus everytime I need to use a new telescope. Works very well for me. If you need further assistance just let me know. But trust me, it will be more than enough to solve your problem. The tilt will be minimum.. Around 4-5% of tilt, but if still bothers you, you'll have the tilt plate to fine tunned. |
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| 🤣 I would be thrilled to get it down to 4 or 5%. I'll post a picture of the imaging train as I have it right now. I did away with the OAG. Just couldn't get it to where I wanted it. Went back to a guide scope and the guiding numbers are great. Easier to find usable stars. You may have misunderstood. The thread coming off the Starizona corrector "is" 42mm male. I've achieved the 90.3 back focus. I'll recheck the collimation and try to better center the corrector in the Click Lock. Then, test again. I'll post my results. Very generous of you to offer your help. Thank you my friend 😁 |
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Hi Mike, Don't get me wrong, but I think most everyone hear is trying to let you know that the Click Lock is 99% of the tilt issue. You need to remove it. Click Locks are for quick changing of eyepieces, as far as I know, there not intended to hold heavy objects stable like camera image trains. |
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Oh Bob I didn't see that at all. I thought the click was the best way to center and support the image train. When I tighten it, the image train is rock solid. I have a common Celestron visual back that uses one or two screws and the typical band of metal that tightens against the 2" barrel. So you're saying that is better? I'm certainly willing to try it. Mike |
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This tilt/spacing adjusting gadget may be of interest - I'm looking into getting one myself.  https://www.asgastronomy.com/photon-cage/ Cheers Andy |
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Andy 01: I'm sorry, but you do not need that kind of kind of adjustment on a C8 and I've never needed anything like that with a Hyperstar based system either. The depth of field on a F/10 system is 250 microns (+/- 125 microns) and that is well within normal machining tolerances for fixed spacers--either threaded or with dovetails. I don't know anything about the Click-Lock that the OP is using but if it is something different than a simple machined spacer, don't use it. With a properly configured and assembled camera package, you should be able to grab the entire image train at the end of the telescope and physically apply a fair amount of force back and forth on the camera and feel ZERO play--and you should see virtually zero sensor tilt. Here are a few things to watch out for: 1) Flimsy components. I once used a Pegasus filter wheel that was made from very thin metal that appeared to be made of architectural grade aluminum with a LOT of mechanical flexure. I could easily see it flex when I applied even a light load so I tossed it out and went back to FLI. In my opinion, that product was a piece of junk. 2) Improperly designed components. I have an Optec Sagitta AOG on my refractor and it is not well designed to avoid mechanical interference. When I first installed it, I wound up with a lot of tilt and I tore my hair out in an effort to find out why. It turns out that the focusing stalk on the OAG is about 0.010" wider than the base and if the unit is placed flush with a FW, that 0.010" wouldn't allow the dovetail to be pulled uniformly flush when everything is tightened down. It was such a small amount that it wasn't immediately obvious what was going on. I finally found the problem by wiggling everything. I found that in one direction, everything was solid, but in the other direction, I could detect just a tiny bit of play. By rotating the OAG to avoid having the focusing stalk next to the FW, I could properly tighten everything to be perfectly flush, which eliminated all but the smallest amount of the tilt--over a 42 mm image circle. In my opinion, the Sagitta OAG is a nice product but Jeff should redesign it to fix this problem. And a fix would be very simple. 3) Normal dovetails that you find on astro-gear are not kinematic. Furthermore, with just three set-screws, a single loose screw will cause a poor fit and possible tilt. When I design a dovetail, I don't generally address the kinematic issues but I do design them with 6-screws. That makes them much less susceptible to loosening during thermal cycles or vibration and much easier to snug flush. Before assembly, make sure that all of the surfaces are as clean and damage free as possible and be extremely careful to check that everything is flush and that all three screws are snug after assembly. If you can insert a "lock" set-screw on top of the three "holding" screws, that can help to prevent thermal or vibration induced loosening over time. Eliminating tilt requires a bit of OCD to make sure that everything is correctly assembled and that eliminates the need for tilt adjusters. As I've said, in most cases, sensor tilt is caused by tilt adjusters. The exception is when you have a much faster optical system using a very large sensor--often in combination with a mechanical focuser that doesn't control tilt very well. John |
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Mike H: No, what needs to be done in my opinion is to remove the clicklock, and don't use the 2" barrel. Even though say the image train feels rock solid, it's probably not. What you need to do if you can is to find a spacer the right length that has threads on both sides. Again, this is just my option, you cannot eliminate tilt when using slip fit adapters such as clicklocks or barrels, there will always be room for movement. |
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Bob, the 2" barrell I'm speaking of is the Starizona Corrector/ Reducer. It has a 2" barrell that inserts into a visual back and the other end is a 42mm male thread. There is no getting around the Starizona unit needing a visual back on the C8. Mike |
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| Got it, I hope you find a solution for the tilt issue. |
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Mike H: Mike, which type of the Starizona Reducer/Corrector you have? can you post here in order so we can give further assistance? |
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Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector As soon as I get home, I'll post a picture of the current imaging train. I did away with the Baader focuser, because I couldn't reach focus, and the OAG. Mike |
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Ok.. that's a 2" barrel corrector with in front a M48 female thread in front and a M42 male thread in the back. I've understood your problem. You have a situation like this guys, but you're using a Baader click-lock insted of the traditional celestron screw holder.. Correct? https://www.youtube.com/watch?v=YkNYixHknFk |
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| That is correct. I was told I would get better centering and a better overall grip on the imaging train. When you crank down that click lock, is isn't going anywhere. |
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Yes in that image format of locking the imaging train, the click lock if the better way exactly for the reasons that you mentioning. Problem is the same system is also making you tilt because he’s not screwed. No matter what you tight things up, part of that 2” barrel of the reducer/flatnner will be induce tilt for the reason that I’ve explain a few posts above. The only way that you can take away the tilt, is by having all the image train screwed. I have two solutions for it, one makes me feel more safe than the other. - The first is to take your Baader click lock adapter and acquire an SCT tread adapter to a male M48 thread. In that M48 treat you’ll thread the reducer/flatnner and the rest of the imaging train fills the 90.3mm backfocus up to the sensor. - The second solution I have to take a picture of some spare parts that I have in order to show you how to pull it off using the Baader or the Celestron adapter. |
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| Your pictures would be great 👍🏻 |
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Well my second suggestion is go to more DIY using one of two things, rubber washers or something think enough to make the 2” barrel do the adapter uniform and tight all way in to the Baader Click lock. I’m using in this exemple a 1.25” nosepiece to simulate the 2” barrel and my 1.25” Celestron adapter to show you how to achieve.    or using a think plastic that are use for making presents in bows.. but remember that I’m using here a 1.25” nosel:    The ideia is that you’re 2” reducer/flatnner enters tight from one point to the other inside the Baader click lock so you don’t have any play.. when you do the click you’ll know that is no tilt inside. I’m not a huge fan of this method but when I was starting my resources were limited, and this method helped me a lot solving tilt issues. But remember everything time you change the configuration or remove the imaging train, check for the collimation. SCTs are notorious for dropping off collimation. like I said, I would go with the first solution. The screwed one. That’s the more reliable. Just have the attention to not put to much stress on the female M48 threads. I can’t see any other way of you solving the tilt. At least that the way I’ll do it. I don’t have the Starizona one. Only the Celestron. |
