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f/6 or f/8 Mak-Newt -- advantages? disadvantages?

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#1 Psa19one

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Posted 29 November 2005 - 03:46 PM

I noticed that the Intes 7" mak-newt is made in both f/6 (M76) and f/8 (M78) focal ratios. Is there a real advantage to having one over the other? I know the f/6 will give a wider FOV (and shorter AP time), but what if I just want to use the 'scope for visual (mainly planetary) use?

#2 bierbelly

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Posted 29 November 2005 - 04:12 PM

I'd think the f/8 would be better for planetary, since it will have a higher instrinsic magnification for any given EP.

#3 wilash

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Posted 29 November 2005 - 05:52 PM

The central obstruction is smaller in the f/8 version and so would be better on the planets because there would be less impact on contrast. There would possibly be fewer abberations with the f/8 also.


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