Re: ATM 6" Dob: How Easy? How Cheap? How Heavy?

[HERVEY LEMAY <HJL@segalco.com>]

> Also, putting screws into thinner plywood doesn't always 
> work out well. I'm visualizing a slightly more elaborate 
> design with thinner plywood but square pieces of wood inside 
> the corners so that no screws have to go end-wise into a piece 
> of plywood. Is that commonly done?

It is commonly done, and can yield an impressively rigid structure.

> Finally, everyone really seems to prefer wooden primary 
> mirror mounts and I'm not sure why that is. A nice, open 
> aluminum mount costs around $30-something which doesn't seem
> extravagant. For a 6" mirror is an aluminum mount like that 
> less stable, durable or adjustable than a wood one? Or do most
> people just have more of a "I built it myself" desire than I do?

The mirror mount will be made from the remains of your sheet of
plywood, so the wood is free.  You can use your father's router to
take out a nice hole from the middle of both pieces of wood, and make
the base plate triangular to leave as much open space such that it
only contacts the tube at the three mounting bolt locations, all in
an effort to speed cooldown.  The 3 mounting bolts, the 3 push screws
and 3 pull screws, with associated t-nuts, washers, and wing nuts
(and springs if you want the luxury), can be bought at your local
hardware store for $2 or so.  Three dabs of RTV adhesive will hold
your mirror to the cell.   Seal the wood and mount it in the tube for
one fifteenth the cost of buying a retail mirror mount.

Hervey