After building my own scope I was contacted by the NBANB to construct a telescope for use by the several clubs that make up the New Brunswick Astronomy assoc. Having learned a few lessons from the experience of my first scope, I have refined my design quite a bit and put it to use here.
I streamlined the design of the mirror cell considerably and reduced to weight by about half.
The main part of the cell is a 17" dia sheet of 1/4 aluminum. I cut out 6" from the middle and bored out nine 2" holes around the circumference of the plate. The triangles for the mirror supports were also made from 1/4 plate as well. The supports are covered at the corners with 1" dia discs of 1/8" rubber. The supports are connected to the base plate with 3/8x3/4 shoulder bolts and are cushioned with two discs of rubber, this gives some the triangles some movement to let them equalize to the back face of the mirror.
Next I machined four posts that bolt to the edge of the base to provide side support and location for the mirror as well as mounts for the mirror clips that prevent the mirror from falling out if the scope gets tipped over.
The mirror cell is adjusted by three screws that thread into nylon nuts bolted to the base plate. The adjuster screws are mounted in the bottom board of the mirrorbox, the retainers are adjustable to reduce any backlash in the screws. The screws protrude from the back of the mirror box and have a 7/16 hex milled onto the ends for easy access with a wrench. This
arrangement works well on my scope and you can align the mirror to perfection with a few tools in just a few minutes.
The basic design was calculated from and article in Sky and Telescope a few years ago and refined further using David Lewis's Program Plop
I did all of the design work in RhinoCad 3D, a program that is one of the best in it's field. Very powerful and very easy to use. Much more intuitive that most of the Cad programs out there. You can download a full version of it from Rhino, it is only limited in the number of times you can save a file. It will give you time to get addicted to it :-)
Here are some additional cad renderings Pic 1 Pic 2 Pic 3 Pic 4 Pic 5
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