Quote:
Originally Posted by Peter.M
I dont know about the viability of these fast newts, the secondary is 90mm which is 20% of the area of the primary. So the aperture is only 160mm useable,
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While your point stands I think your maths is a little off, and it's not quite as bad at that.
200^2 = 40000
90^2 = 8100
40000 - 8100 = 31900 = 178^2
Which is still a significant reduction it's not quite as bad as to 160mm.
Quote:
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Originally Posted by CometGuy
So is it f2.8, f2.9 or f3.0?
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And is it 8 inches or 200mm?