Re: [ATM] Cass mirror separation

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

Been through this one myself and what I did was put together the
scope and moved the secondary until the image formed at the right
location.
The primary was mounted on a wood stand with an eyepiece about 3"
behind the back surface of the primary for a start.  The
secondary was put on another stqnd which held it at the right
height.  The whole thing was pointed at a bunch of buildings on a
distant hillside about 3 miles away.  Moved the secondary to
where it approximately was supposed to be and then went to the
eyepiece and focused the scope on the diatant hillside.
That gave me the rough distance for the primary to secondary
distance.
After making the tube with a temporary secondary holder that
would allow for a lot of piston on the secondary position, I then
checked the scope out against a star (Polaris is always a nice
choice!) and checked out the aberrations of the scope.  I found a
fair bit of spherical aberration so I ended up moving the
secondary a bit and got rid of most of that problem.  Last step
was to replace the secondary holder with one that was a bit more
accurate and sturdy but didn't move as much.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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