Re: [ATM] Re: 25" mirror possibilities

["Bob May" <bobmay@nethere.com>]

The form for a Gregorian is a parabolic primary and an eliptical secondary.
The quick and dirty is to put the secondary so that the focal plane of the
primary is one focus of the elipse while the resultant second focus is the
final focus of the scope.  This means that you can do a modified Gregorian
where the secondary is off to one side, the light path being bent by the
flat to go across the incoming light path at some point shortly before or
after the focus of the primary and thus the Gregorian secondary can have a
magnification of about 2, making the scope a fairly low power wide angle
scope.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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