🚀 go-pugleaf

In article <C0rD9F.CMr@cantua.canterbury.ac.nz> adm@phys.canterbury.ac.nz writes:
>
>The astronomers here have a 1m telescope that uses a C8 for a finder,
>and they've done just this, except that when they found the right place
>for the mirror, they flooded it's cell with epoxy resin and stuck it in
>place! I've never seen what this scope can do myself, but it is reputed
>to be very good.
>

Sounds like a great idea, except for a couple of flaws (not that you guys
did it wrong, but anyone who might want to try this had better worry about
these problems.

First, A large amount of epoxy can release a fair amount of heat while
curing. This could possible distort things, then leave them that way forever.

Second, epoxy is something of a thermal insulator (not a great one,
though), adding a lot of epoxy can add a fair amount of thermal mass,
reducing performance while the scope is trying to reach thermal equilibrium.

Third, your screwed if it goes somewhere where you don't want it!

I've recently acquired a used 8" SCT with such a problem. One way I fix it
is that I notice the error is different if I approach final focus from
outside as oppposed to inside. So my technique is to find focus, overshoot
slight to the outside, and back into it. Seems to reliably work. In my
case (a Dynamax 8000 that I picked up for a couple of hundred dollars),
there may not be enough back focus available for a new focusser and a
guider and a focal reducer and a camera.


-- 
|                Dick Pierce                |
|    Loudspeaker and Software Consulting    |
| 17 Sartelle Street   Pepperell, MA  01463 |
|       (508) 433-9183 (Voice and FAX)      |