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Old 17-11-2012, 10:19 AM
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MortonH
Deprived of starlight

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Join Date: Nov 2006
Location: Sydney
Posts: 3,907
Quote:
Originally Posted by cometcatcher View Post
I realise that a doublet will have "some" CA still, but my little Kson ED80 is a doublet at F5.5 also, like the Long Perng, and it's colour correction while not perfect is far better than the LP. That's why I went for the LP, I thought it would be in the same class as they are both F5.5. I believe the Kson uses a FPL51 glass element.

Kson ED80 pic for comparison.

Hi Kevin,

For a given lens design/glass type, CA gets worse as you increase aperture.

Agree with the above suggestion to get one of the Skywatcher/Saxon ED80 scopes with FPL53 element. They are effectively colour-free and lots of people here are using them for photography.

Morton
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