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Old 14-10-2011, 07:32 AM
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gregbradley
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John, I think Bert is right. I remember Richard Crisp posting Tak Epsilon 180ED F2.8 images and same with FSQ106 images of the same object.

It required something like 3-4 times more exposure in the FSQ to match but to my eye the FSQ images looked better as they were finer.
Its probably on his website somewhere.

With regards to coma in images in the RH200:

Massimo Riccardi responded to a post I made about the images showing coma.

He said that it wasn't coma and was caused by the imager using 50mm round filters which partially block the sharp F3 light cone affecting corner stars.

So I guess that question of the corner stars is up in the air until someone produces an image using 50mm square filters (I assume when he says 2 inch filters he means 2 inch round).

By the way Bert he said it was designed to handle 24 x 36mm cameras.

I am not sure how that works with the 16803 which requires a 52mm diagonal of corrected circle. 24 x 36mm is a 44mm diagonal. So some corner problems may occur which can be handled by cropping the image or by using a smaller chip like 11002 or similar. I'd stick with the 16803 and crop if needed as the 16803 is such a super chip and if you use it with anything else (like your Canon lens) it will be worth the extra chip real estate.

Here is his post:

Greg,

as it often happens dealers can make mistakes on their advertising.
It's the bigger Veloce RH 300 F/3 covering about 60 mm field.
On the contrary I designed the smaller 200mm F/3 for covering the full 24x36mm
format.
For 600mm focal lenght the 43 mm diagonal corresponds to 4 degrees which is just
the field covered by this instrument.

About the coma you mention it is not coma.
I hope Giovanni Paglioli (the astroimager)will post here the explanation but
from what he told me what looks like "coma" is due to the 2" filters size which
is not enough for covering the large F/3 beam reaching the focal plane and this
fact "cut" the stars at the edges.
Without filters this doesn't happens.
I'm not an expert in this field and Giovanni will give you a deeper
explanation.

Massimo


Greg.

Last edited by gregbradley; 14-10-2011 at 07:44 AM.
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