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Old 24-12-2012, 06:55 AM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
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Quote:
Originally Posted by AstralTraveller View Post
I have a GSO 10" and it's nice enough. The 10" is basically the same length as the 8" (due to the shorter f-ratio) though fatter but collects >50% more light (the actual ratio is 100:64). It can't beat my 6" refractor on planets or the moon but it eats the refractor on DSOs.
Hi David,

If your 6" refractor is outdoing you're 10" dob on the moon and planets, I think something isn't quite right with the 10" dob.

I think one of the following issues may be at play:-

1) miscollimation.
2) thermal cooling and stability issues.
3) an astigmatic secondary mirror which can be easily fixed.
4) a dud primary mirror, which isn't so easily fixed.

I have two 10" dobs, one is a 10"/F5 with a very good GSO mirror (the secondary was astigmatic when I got the scope) and the other is a 10"/F5.3 SDM with a Mark Suchting mirror. There isn't a 6" refractor on the planet which will outdoor either telescope as a lunar/planetary instrument.

Cheers,
John B
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