Re: ATM Primary Cover

[Archer Sully <archer@meer.net>]

On Saturday 09 February 2002 07:22 pm, "Jim Miller" <jim@jtmiller.com> wrote:

>
> Mel had previously suggested a circular plastic lid which is held in place
> by vacuum and I like that idea but I'm worried about the lid actually
> touching the surface of the mirror and also I need to provide edge
> protection.  Here's what I'm thinking and I'd appreciate feedback.
>

My situation is a bit different, as my mirror is perforated and thus
can't hold a vacuum, so here's what I did:

Got a piece of mirrored plastic cut to the same size as the primary.

Cut a strip of formica-like-substance to match the circumference 
of the primary plus a bit, and a scootch thicker than the primary's 
thickness. 

Wrap the formica around the mirror, and tape thoroughly.  Tape the
plastic to the band.   This protects the mirror quite well, and has the
additional beneficial side effect of confusing the heck out of people
who look at the scope during the day at star parties ;-).  

You really don't need to worry all that much about touching the edge
of the mirror, as you'll be hitting the top of the bevel and not any part
that contributes to the image. 

Going oversize and then padding to make the top plate stay in place
probably won't provide a very good seal, and it is likely that dust
will end up on  your mirror face anyway, although this will protect
it from cat paws, bird droppings, etc...

Archer Sully
Boulder, CO