Re: ATM which one first

[David McCarter <mccarterd@claven.fanshawec.on.ca>]

>1. I have looked at different kinds of focuser, Ilike the helical the
>best. Rack and pinion are fine but just doesn't appeal to me. Is there
>any draw backs of this type? Is there a general "best"?

The helical takes forever to change focus if your eyepieces are not
strictly parfocal. I thought I would like them too, but discovered I had
not enough patience.

>2. Upon construction, Which one is wise to make first, The mirrors or
>the base and tube? I want to make the base and aall of the other stuff
>before the mirrors. Any comments?

Mirrors. If you don't know the final real focal length of your mirror you
will do a lot more cutting, and it is real hard to make a tube longer. One
of the requirements is to figure the centre of gravity of the optical tube.
For that you need the mirror in it's cell. Make the mirror first.

>3. Whats easier (Time wise) to make 8" f/8 or 8" f/6?

Either. There is just a little more glass to remove from an f6, but the
real time in making a mirror is in the polishing and figuring, and they are
about equal in difficulty to get a great result.

>4. A parabolic curve is sunk in.(can't really explain it). Whats a
>sphere?(spherical)?

Yup. It's wierd. You can get a spherical surface almost automatically just
by the stroke of polishing. From there the edge is pushed down to make a
parabola, or the center is dug out to make a different parabola of shorter
focal length, or both edge and centre are moved to make a parabola about
the same focal length as the sphere.

>What is the ultimante goal for making a mirror?

Pin point star images!

>5. Who funds this mailing list ?

We do. When this list was set up some of us antied up, and I understand the
funds are still alright for a while. Mel does a fine job of keeping
everything, including us, on the straight and level. Of course it's easy
for him. He is a pilot. :-)

Dave