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ComaCorrector with a Filter Wheel

TRIXMASTA
05 Aug, 2019 06:47
Good morning,

Iam using the Baader Comacorrector MPCC Mark III on my Skywatcher 200/1000 PDS and also filters. The filters were putted infront of the Comacorrector, so that the light have to pass the filter first. To prevent my setup from tilting Iam using the Lacerta FUFmpcc to srew the whole imaging stuff to the OAZ.
Now I want to put all my filters into a filter wheel, but Iam not sure if the focus can still be reached. So Iam thinking about putting the filter wheel between my ASI 294 and the Comacorrector. Do someone know if this setup will work? Iam not sure because of the diffrent way the light might be refracted. Any Experience with that?

Thanks in advance,
Daniel
micvon
05 Aug, 2019 21:11
The coma corrector has an optimal distance from the camera sensor in order to have a field fully correctd. For most brands it is 55mm, just check the specs of your coma corrector. You just have to make sure that all the elements in your optical train (including the distance from the sensor to the threaded ring of the camera, also called back focus ) sum up to 55mm or whatever is the optimal distance for your coma corrector. Check this page out…the image at the bottom should be what you are looking for : https://astronomy-imaging-camera.com/tutorials/best-back-focus-length-solutions-55mm.html
TRIXMASTA
06 Aug, 2019 06:17
Thank you for your answer Michele,
I know that the camera and the coma corrector have to be in an optimal distance. It is 55mm for the MPCC Mark III. I have this distance already adjusted.
But my question is about the use of a filter wheel between the corrector and the camera. On many sites i have read that the filter needs to be infront of the coma corrector. So I am quite unsure if I can adjust the filter (the filter wheel) between it. If I put the filter wheel infront of the correcor my backfocus will be extended. The reason is, that I actually screwed my corrector inside my OAZ. Because this is the most solid way to pretend the whole setup from tilting. While the wheel infront of the corrector not can be screwed inside the OAZ and I will get my tilting problems again. Maybe using a filter drawer is anothere option, because its more thin then a wheel. I think I have to give it a try.
 
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