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I occasionally host star parties on YouTube and Discord. Is there any interest in this forum to participate and chat during those long imaging sessions? Equipment Varies: RASA 11, 8" RC, Meade 10", various refractors. ZWO 533mm, 6200mc, 6200mm and assorted smaller cameras Sharpcap, APT, ASCOM, CPWI, Chrome Remote Desktop Shamrock Banks Observatory MPC Code W24 Bob Townsend
Rasa11 and back focus issue?
b1ues posted a topic in Discussions - Scopes / Whole setups
Having started AP a few years ago when I was introduced to it by a friend (probably around 2015/2016), unbeknown to me and oblivious to the possibility of achieving such wonderous images, I began my pursuit with nothing more than an advanced digital camera (Canon G16) and a photo tripod. The first true session at a dark site with this equipment revealed the wonder of the milky way and the best image of the night (full of chromatic abberation and false colour of course) was of an arm of the milky way with a faint Andromeda visible and to top it off a meteor streaking across the image. Since then I have been building up equipment, selling off things which didn't quite work for me and waiting to visit the dark skies again. Commitments, bad weather etc got in the way of course until I thought why don't I try from my light polluted back garden? Low and behold, things were possible to be imaged (hence why I image more than do visual), and imaged better than I thought was ever possible. So I have been eagerly trying new things, different setups, different challenges, I don't think I'm comfortable unless I'm tinkering with something or trying something new. I started this in 2021 so i've only been doing it just over a year approx. Having had an interest in many things cosmology I thought it an interesting thing to pursue. DSO's are what primarily interest me, but generally I believe anyone can get a sense of wonder from seeing anything beyond our atmosphere. Earlier this year I started my first full length project, NGC7023 the Iris Nebula, a difficult target but is always visible in the sky so a good one to do. Having spent 24+ hours gathering LRGB data via mono, I was happy I got some sort of result but a bit discouraged that it took so long (10+ sesssions. I've seen many people with a lot more dedication to targets). I know this hobby isn't for the impatient but lack of opportunity to image does make one wonder. So I thought about my options. I had initially tried a 0.65x reducer with my refractor to test the faster f ratio waters. Still wanted more. Then I tried the venerable Samyang 135mm, and it's a wonder to use. But I still wanted more. RASA piqued my interest but I'd need a larger mount plus the associated costs to get the rig running. Was there anything out there that I could potentially still use with my most used mount (AZGTI?, I do have another heavier duty mount also). Enter the Celestron C6 OTA. Then there was Starizona's Hyperstar. I have truly felt the need, the need for speed... It's taken me a few weeks to get this working to a degree, I'm still not quite there yet as there are a few issues I still have which you can see in the following image, but managed to test out imaging on three targets in one night. I understand they won't be the best quality but I'm glad I managed to get something in a fraction of the time I would normally, I couldn't quite put a figure on it yet, a lot also depends on post processing skill but I still do this manually at the moment. An easy first target (technically the second) as it's relatively bright, a bit too bright at F2 so I imaged it at 1s and 10s subs, total time, 10 minutes, M42 The Great Orion Nebula (will add more data at some point, definitely better than my attempt a year ago): So I've started this thread for any other speed runners out there running faster than "normal" setups, and also a place to discuss potential issues and solutions. There is already an excellently large Samyang 135mm thread by @Uranium235 so users of this lens please continue to post in the "Imaging with the Samyang 135mm f2" topic.
Strange star elongation issue
angryowl posted a topic in Discussions - Scopes / Whole setupsI’ve been struggling with elongated stars for the past few months now and have tried numerous things and read through similar threads here and on other forums with no success. This is really starting to get to me as I’ve lost track of the number of clear nights wasted so far. The elongation direction is not consistent at all and varies over different parts of the sky. The kit: Mesu 200, Celestron RASA, 60mm StarGuider guidescope, QHY5L-II guidecam, Atik 414EX main imaging camera, Baader UFC, Baader F2 High Speed narrowband filters. Things tried so far: Tested for cable drag and recently started routing all cables coming off the scope at the back of the dovetail. Both RA and DEC balance is spot on. This was performed several times with a digital fishing scale and the balance points marked. I’ve always used SharpCap for PA but also tried several runs of PHD static and drift alignment with the same results. Read the entire SiTech Operations manual for the Mesu as at one point I was getting elongation mostly in Ra and though the mount may not be tracking at a correct sidereal rate. There’s a method of calculating the proper track rate and have spent a couple of imaging sessions doing this with limited success. The method involves measuring the drift of a star in Ra in an interval of 10 minutes. Then after some clever math, one can change the Ra motor ticks in the ServoConfig configuration for the mount. This worked, but only for the position in the sky where the drift was measured and as soon as the mount was pointed to another part of the sky, the issue would immediately reappear. What’s worse is that the same tracking rate would no longer give round stars on a different night in the same position in the sky it did for the night before. Short exposures of a minute or shorter in any position in the sky give perfectly round stars. This eliminates collimation, issues with the camera or any other optical element in the light path as I see it. Differential flexure between the main scope and the guide scope is a non-factor as I get elongation during unguided exposures. Tried tweaking the settings in PHD2 thinking I might be able to guide it out. Results, again, vary depending on the night and position the scope is in. Sometimes guiding would give almost acceptable stars and some improvement over unguided and other times it would simply make matters worse. Additionally, rotating the camera 90 degrees results in the direction of elongation being rotated as well. The camera is coupled to the front corrector plate via screw adapters which I simply can’t see flexing. The only time I can get round stars is with the scope pointing near the Zenith. I’m at a point now that the only thing making sense is flexure within the RASA or imaging train. I know the camera is tightly fixed to the corrector plate so there can’t be any play there. The only place where flexure could occur would be at the main RASA Losmandy mounting plate. The plate is screwed in to the front and back aluminium holders by four M5 screws I believe. Thought these might have loosened over time but after checking, they’re as tight as they’d go. Not sure how solid a RASA should be and I didn’t really test or look at this when I got the scope as there was no need, but when fully mounted, the scope can be easily rocked by applying light pressure to the top mounting plate. This is not an issue with the Mesu head as it’s simply rock solid and can’t move it at all regardless of the force applied. At this point it’s all pointing to the scope/mounting plate flexing due to gravity as the scope is not exactly light. This could explain the odd behaviour throughout different parts of the sky as the scope is flexing in different directions. Trying to determine if it is indeed the scope flexing, I’ve done some testing yesterday. Setup everything as usual during the day and focused on a brick wall roughly 30 meters away on a day with no wind. Mount was off and both axes were locked with the mount hooks, so mount tracking errors or movement would be eliminated this way. Started with 5 short consecutive exposures, then at 10 minute intervals another 5 exposures were taken until 40 minutes elapsed. Each set of 5 exposures were integrated in PI using an average combination with no normalisation or any pixel rejection algorithms. This was done with the scope on both the East and West side of the pier pointing at the same brick wall and with the mirror both locked and unlocked. Combining these integrated images into GIFs and plotting the Ra and Dec orientation clearly shows considerable drift over the course of 40 minutes. As can be seen the drift is not purely in Ra or Dec, but a combination of both. Mirror locked. Scope on East side of pier. Mirror unlocked. Scope on East side of pier. Mirror locked. Scope on West side of pier. Mirror unlocked. Scope on West side of pier. These next four GIFs show the result of pushing on the scope’s top mounting bar. The direction of movement when applying pressure on the scope is very similar to the direction of drift in the first two GIFs. If I’m not mistaken this would indicate that the RASA is indeed flexing/sagging due to gravity. The scope was purchased from FLO about two years ago. Would this be considered normal behaviour or am I just barking up the wrong tree here? Mirror locked. Scope on East side of pier. Before and after pressure applied on scope mounting bar. Mirror unlocked. Scope on East side of pier. Before and after pressure applied on scope mounting bar. Mirror locked. Scope on West side of pier. Before and after pressure applied on scope mounting bar. Mirror unlocked. Scope on West side of pier. Before and after pressure applied on scope mounting bar. I find it hard to believe that the image should drift this much over the course of 40 mins, but then again, I may be wrong and this isn’t out of the ordinary??? Any help with this from the awesome and knowledgeable SGL comunity would be greatly appreciated as I’m simply out of ideas and things to try.