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Old 21-09-2017, 07:13 AM
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DiscoDuck (Paul)
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Flattener and reducer for RC

Just trying out the CCDT67 reducer to get some decent arcsecs per pixel with the ASI1600 on an RC8 scope.

As per advice online, I find that around 65mm spacing from the sensor gives good results in terms of field flatness - but gives a reduction factor of about 0.74 compared to the 0.67 you get at 85mm spacing.

At 85mm the corners of the image are not good and even at 75mm noticeably poor. But ideally I'd want to increase the spacing somewhat to go up a bit from the 0.66"/pixel I'm at now.

My question is whether anyone has tried to use the CCDT67 in combination with a flattener - such as the TSRCFLAT2 (from TS optics). This has a generous backfocus (109mm) so might work?? But not sure of the interplay of the optics. Or is there a good 2" barrel combined reducer + flattener for RCs I've not come across?

(The advantage of the 2" barrel reducer and flattener is I can stick them inside the focuser and still have enough room for collimation ring and rotator at the front and OAG, filter wheel, etc at the back. It's getting a bit crowded there!!)

Thanks for any advice.

Paul
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Old 21-09-2017, 09:04 AM
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Crushellon (Tim)
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To the best of my knowledge, you can't use a seperate flattener and corrector in tandem. It's either one or the other.

Tim
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Old 30-09-2017, 02:26 PM
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DiscoDuck (Paul)
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Thanks Tim. Worth asking!
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Old 30-09-2017, 03:53 PM
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RickS (Rick)
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Some reducers will also flatten a little, e.g. the Astro-Physics 27TVPH.
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Old 30-09-2017, 04:12 PM
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DiscoDuck (Paul)
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Quote:
Originally Posted by RickS View Post
Some reducers will also flatten a little, e.g. the Astro-Physics 27TVPH.
Thanks Rick. I notice that one's only 0.75x reduction though, which is what the CCDT67 can give me without too many problems in the corners.
(and may not satisfy my requirement to fit inside a 2" focuser tube - I don't ask for much!! ).

Thanks again though.
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