Re: [ATM] Re: 25" mirror possibilities

["Jean-Guy Moreau" <jgmoreau@cablevision.qc.ca>]

> "Has anyone made a system like this?"
> 
> Gene Cross has. He tried to popularize the design back in early '90s. He
> used very fast primary,
> close to f/1 (it went under something like "20" backpack telescope"). He
> was even talking about
> some sort of "breakthrough" in regard to not having to aspherize primary
> - if I remember correctly - 
> but all went silent afterwards.


Now this is getting interesting, not having to aspherize the 
primary  :O)

cross axis Gregorian with tiny diagonal to boot !

what figure would be the Gregorian secondary then, if we want
a reasonable configuration with the secondary on one side of the tube
and the focus on the other side ?
for example for a 24" f/2 spherical primary, while we are at it, 
can it be an aplanatic ?
field curvature ?

Jean-Guy


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