[ATM] Nasmyth secondary mirror cell ?

[Don Anderson <donanderson@direcway.com>]

I am trying to design (before attempting to grind and build) a Nasmith Dob.
I will have a 22 in.f/6 primary, an 8 in. secondary, and a 2+/- in.
tertiary.  The secondary will be as optically flat as I can manage and will
be perpendicular to the optical axis, thereby avoiding astigmatism.  I have
thought of two designs for the secondary mirror cell.  I am not satisfied
with either and am open to suggestions.  The designs are:
1. full thicknes mirror glued to the cell with clips for safety.
2. the mirror face sitting on three pads which are supported from the sides
with a sling to support the mirror on the side.

I am interested to hear any comments about these and/or a suggested design.
Don

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