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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.
I am looking at introducing an OAG to my current imaging setup. I use an Atik 383l plus Atik EFW with a skywatcher aplanatic coma corrector with a 10" skywatcher Quattro.
The obvious choice would be an Atik OAG but with only 55mm of back focus available on the coma corrector I assume I'll need a narrower OAG.
Any help/advice would be great appreciated.
I have a revelation (GSO) coma corrector that I use on my 130 pds with a Canon 1000d. I have noticed that I am still getting some coma. My question is, do I need a spacer between the corrector and the T ring. I can't find any definite information on this but I read somewhere you need 75mm between the rear element and the camera sensor
Had another go at getting the spacing right on my Imaging Star 80
Some arithmetic on the spacing and making some assumptions about the thickness of components gave me a suggested spacing of 44mm from the end of the focuser.
The nearest I could get was 46mm, which is still a wee bit too long and there's a lot of tilt to sort out, probably with the Bahtinov mask. Oh, yes and a couple of horrendous dust spots and some localised gradients which I've tried to get rid of with flats, though not entirely successfully.
Total integration time 40min made up of 40 x 30sec and 20 x 60sec. Exposure took place as the sky was getting dark, and I think there were flecks of high cloud coming over as well, hence some of the gradients.
Can anyone offer any advice or tips to reach focus using an off axis guider, with a guide camera attached and a CCD camera for imaging? I had a nightmare with a previous CCD camera (now returned) and want to try again with my new imaging CCD camera. I have spacer rings for both the cameras, but no fine adjuster for focusing properly.