Ad Astra Observatory

Hi Paul,

Here’s a page with some photos of the kind of thing that I’m thinking
about building around my new 13.1” f/4.5 mirror.

The major design dilemma will be to keep the telescope as lightweight as
possible, since my mount is limited in the amount of weight it will

carry. So the plywood rings + tubes idea (as opposed to this, which is
what it used to look like:
http://www.flickr.com/photos/ambroseliao/2343871046/) feels like a good one.
Here’s a page with rings+tubes:

http://www.plettstone.com/products.htm

If you look closely, you’ll see that the plywood rings are not round. In
particular, they’re a little wider where the poles come through the

“rings”. Here’s the shape I’m thinking about using:
http://en.wikipedia.org/wiki/Reuleaux_triangle
The shape looks tough, but it’s very simple to construct with compass
and straightedge. Round the corners a little and there’s lots of room
for a nice round hole in the center with room to spare at the corners
for tubes and no sharp edges.

Going lighter by substituting bowstring and tension instead of aluminum
tubes and flexion might end up being a solution. Here’s an example (I’ve
actually used this very telescope — the thing weighs next to nothing
because the “tubes” are about 1/4” in diameter:

http://www.craigcolvin.com/Astronomy/string_scope.html

The design will take a certain amount of head-scratching (which I think
is fun, and you may agree), but I think that the construction will be
pretty straightforward once the pieces are laid out.

Anyway, if you’re interested, this is going to be a summer project for me.

Best,
Jimbo