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About Callistarus

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  1. I'm sure this is just one of many hundreds of posts about correct spacings on here - I think I've just about got it but I need to confirm a couple of things with folks who have more experience than me on these matters. My scope is a Skywatcher Evostar 80ED-DS Pro - one which I'm sure anyone here is familiar with and needs little introduction. I'm using the accompanying field flattener/reducer, which requires 55mm of back focus. The off axis guider I plan to use is an OVL Off Axis Guider - it is thin enough that in combination with my camera I should have the required back focus provided the connecting T-adapter is thin enough. My camera is a Canon 550D (mod), which as far as I'm aware will occupy 46.5mm of back focus. My question is, what would be the best way to connect the Canon to the OAG? Puzzlingly it seems the OAG has a 42mm screw-ring on the camera side, which I don't have an adapter for. Do these exist? Are there any thin models available such that I meet my back focus requirement? If there are any other issues with what I'm suggesting please let me know. It's always easier to nail it first time than faff around with ordering adapters only to discover they're the wrong size. Cheers.
  2. Cheers for the suggestion. I'm not entirely sure how I would go about fitting one of those though. I can see that in the top of the tube rings there are two holes, would that have something to do with it? I agree the OAG is overkill, but I'm looking at it with a bit of futureproofing in mind, as well as avoiding the problem of the wee finder dewing up (despite a dewshield). Is it definitely not worth getting an OAG here? It would be quite reassuring to be able to slap one on the end of the scope with the assurance any flexure in my setup would be eliminated.
  3. Hi all, My setup consists of an NEQ-6 with a Skywatcher 80ED-DS + .85x Focal Reducer. I tried to guide using the 9x50 finderscope that came with the telescope kit (worth about £50) and a ZWO-ASI 120MM CCD camera. I went for 10 minute subs, and verified this wasn't pushing my polar alignment by sticking around for the first sub to come in, and hooray, pin-point stars. So I set it up to take more exposures for the next couple of hours, went and had a brew and put my feet up. I've come to inspect my subs, and have found almost all of them have some kind of minor error. I believe it to be caused by differential flexure, and so am looking at the possibility of using an OAG instead. I have my eye on this specimen: https://www.firstlightoptics.com/off-axis-guiders-oag/off-axis-guider.html which seems to be well-suited to my needs. My problem is, the adapter jargon is a little scary for me. My thinking is to attach the OAG after the focal reducer, which FLO have verified the OAG is designed for, and then attach my guide camera to the off-axis. I understand the need to focus the guide camera, so I was thinking I could attach one of these between the two: https://www.baader-planetarium.com/en/baader-focusing-eyepiece-holder-1%C2%BC%22--t-2--(t-2-part-08a).html and my question is, will this work without the need to buy any more adapters? I'm pretty new to this and this is pretty much a sanity check before I throw away a hundred pounds because of my own ignorance. Thanks for reading :)
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