From: "Dave Richardson" 
To: atm{at}shore.net
Reply-To: "Dave Richardson" 


I'm thinking of building a telescope using one of those cheap 8" f3.7
mirrors from Ebay.  (I really need a project and don't have much money
right now).

The problem is that my secondary size is approaching 30% (by diameter) of
the primary.  How bad will this effect the image, and am I risking the
dreaded black spot syndrome from using too large a secondary?  (my
tentative calcs show that I'll be using a secondary of about 2 to 2.2
inches.)

Thanks in advance

Dave

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