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Old 10-10-2009, 09:09 PM
TheDecepticon
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Why can I see my primary mirror?

Has anyone got any idea as to why I would be seeing this in my images? I first noticed it as small reflections to the side of bright stars, so tonight not being great skies, I thought I would change a few things to see what would happen. Nothing has changed, I think it has accentuated it. Camera is a QHY8 and scope is a 200mm f5 reflector. I never seen this with the DSLR or the DSI Pro. I'm about to set up my M110 and see what happens with that.
Thanks.
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Old 10-10-2009, 10:02 PM
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Tandum (Robin)
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Looks like a reflection from the front camber window.
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Old 10-10-2009, 10:54 PM
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You must be right. Here is a shot through the M110 and it is evident behind Achernar as well as a lighter one along side it with a spurious reflection coming off of the star itself.
I'll turn the camera off and wait 10 mins and pull the UV/IR filter out of the imaging train and try a couple more test shots.
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Old 10-10-2009, 11:11 PM
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A number of people have found that the sensor on these qhy8's is not square in relation to the rest of the camera. To me that little circle to the left of bright stars looks like your sensor or the whole camera, might be offset and showing a reflection. ie: it's not square to the rest of the scope.

I had a lot of reflection issues with my little mono camera and fixed them all by slapping an idas filter on the front, don't ask me how it fixed it, it just did.

Why do you have an IR filter in there? There should be one in the front window.

Totally clouded over here now
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Old 10-10-2009, 11:54 PM
TheDecepticon
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The UV/IR filter I'm talking about is the one that came with the camera. Ive just taken it out of the camera and took a shot with out it and I can't see any reflections at all. I have posted a comparison pic. If the sensor was not square, I would get an off centre reflection no matter what was in the imaging train, I would have thought. My normal setup is
camera>original UV/IR noise piece> extender tube>mpcc>IDAS LPS P2 filter(image 1).
I then tried this combo
camera>extender tube>UV/IR nose piece>mpcc IDAS LPS P2 filter(image 2).
I then tried this combo
camera>extender tube>mpcc>IDAS LPS P2 filter(image 3).
I'm about to try this combo
camera> original UV/IR nose piece> extender tube>IDAS LPS P2 filter.
I really think at this stage it is an original nose piece filter problem. I have to take a couple more shots before I can say for sure, but that"s what it looks like.
Any other suggestions I could try apart from pulling the camera apart?
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Old 11-10-2009, 12:25 AM
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Damn, you're a braver man than me. That optic window you removed seals the sensor camber which runs at below zero. I rely on that window frosting over rather that the front of the sensor. eek!
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Old 11-10-2009, 06:37 PM
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This is the last shot from last night. It is with the UV/IR nose piece but no MPCC. So my thoughts are it is a combination of the UV/IR glass and the MPCC. Multiweb had re-iterated about this in another QHY8 post, but I didn't fully understand.
His suggestion is to use no glass in the nose piece, space the MPCC as required and use a UV/IR filter in front of the MPCC or a bit further out if possible.
Stars in the last image aren't too bad towards the edge, I might run a few 10min exposures with out the coma corrector and see how they turn out. May not need it on the M110, but I may be back for experimentation when the WO reducer/flattener gets here, I'll play it by ear.
Thanks for your help!
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Old 12-10-2009, 09:24 AM
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i occasionally get this with the DSLR and the QHY8 mate, its a reflection from the inside of the MPCC

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Old 12-10-2009, 03:33 PM
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Yes, I think you are right. I'll have to do something about it though.
I will try multiweb's solution and see what happens. Will be a while before that happens, I think.
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