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Old 19-08-2008, 10:03 PM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
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Quote:
Originally Posted by AlexN View Post
If memory serves, you need a 16" newtonian to achieve 6" of unobstructed aperture... obviously its more weight/space efficient to have a 6" refractor, but it can be done...
That's not remotely even in the ballpark. Mark gave you the correct formula a few posts ago.

"As a rough rule of thumb the equivelent contrast transfer function will be equalled by a quality reflector of diameter larger than the refracter by the diameter of its secondary."

An 8"/F6 newtonian with a 1.52" secondary will perform at a level similar to a 6.5" refractor and that's what all the physics points to.

If, a 16" reflector is properly set up it will outperform a 6" refractor by so far its silly to even discuss them in the same sentence.

Cheers,
John B
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