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Old 09-07-2008, 08:25 PM
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multiweb (Marc)
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QHY8 on Orion ED80

Hi all, I know there are a few QHY8 users out there now. What 2" good field flatener/focal reducer would you recommend for this? What's working for you? Thanks for any advice.
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Old 10-07-2008, 09:08 AM
gbeal
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Depends a little on your scope. In my case I have the Lomo/TMB 80 f6 and it is a pig for requiring the genuine Televue 0.8x reducer/flattener (read expensive as well here).
Of late I have had made an adaptor that fits between the QHY8 and the Baader MPCC, this adaptor being the exact distance to provide the required 55mm or so of spacing. As a result I have been using the Lomo with and without the reducer and having a ball.
Others have asked this before and some use the W/O reducer, others a Celestron or similar, do a search.
The same supplier sells a QHY8 to Nikon or Canon adaptor, and I am sure he could possibly supply the Pentax, although the Canon and Nikon are more mainstream (this is in reply to your Pentax to QHY query).
Gary
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Old 10-07-2008, 12:19 PM
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multiweb (Marc)
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Cool - I found the thread and downloaded the PDF. I understand I need to have 55mm between the base of the MPCC and the face of the CCD chip right? I assume the MPCC outer diameter is a tight fit inside the 2" focuser? I mean the whole assembly once screwed on the CCD slides right in like an eyepiece? I'm not worried about the ED80 [F7.5] but the 5" Celestron is F5 and I have probably 10mm left to travel in before I get an "in focus" problem. I could not reach focus with the Pentax. I now can with the QHY8.

Next question. The two nose pieces with built-in filters provided with the CCD have a Female T thread on the end. Is it ok to screw the MPCC directly after the nose piece? Then get a spacer to match up to 55mm to the CCD face? Or would you just screw the MPCC into the CCD with a spacer then put the filter on the other side? Provided the MPCC has a similar T thread? Is this advisable?

My understanding is if you pile up filters/lenses you might get reflections and halos with bright stars.
What's the best combination? Minimise distance between the glass parts or have them further apart?
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Old 10-07-2008, 02:25 PM
gbeal
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Marc,
Yes, 55mm from the rear end of the MPCC and the chip. In your case (assuming you have the newer QHY8) there is about 21mm of distance, chip to front of the "nose-piece" (where the IR/UV filter resides). So you need a spacer that is 34mm. This needs a male T thread on the rear, and a female T thread on the front, allowing it to screw into the "nose-piece" and accept the MPCC. I would not remove the already in place nose-piece, merely screw to the front of that from now on. It forms a seal of sorts for the chip, so don't mess with it.
Does this make sense.?
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Old 10-07-2008, 02:46 PM
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Yep - makes sense. Just need to source those spacers now. Thanks for the tips.
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