RE: ATM 16" "sling"?

[Krajci Tom J Maj 27 OSS/IN <Tom.Krajci@cannon.af.mil>]

> From: "designsdavis" <designsdavis@home.com>
 
>    Ken,,,,,,,   You have caused me to ask another question.
>                     What is a "sling" ?

In some styles of mirror support (especially larger amateur scopes) a sling
is used to support the mirror's weight along its edge, when the scope is
pointed close to the horizon.  (This is the kind of mirror cell where the
mirror can slide about on teflon pads that support the mirror's back..also
mirror restraining clips are used to keep the mirror from falling out of the
cell it it's tipped forward.)

*IF* you feel you need a sling (or similar edge support scheme)...make it of
a material that does not change length with changes in humidity...steel
banding, bicycle chain, etc. will work fine.

However, I (and many others) don't feel a sling is needed.  Design and build
a good support system (how thick will your mirror be?  My sixteen inch
mirror is 1.5 inches thick and is on a six point support), and then RTV
silicone glue your mirror to the cell support pads.  No sling, no retaining
clips needed, collimation is held very well at all elevations.

I recommend you download PLOP and tinker with various support schemes for
mirror cell designs...we'll help you if PLOP seems to be a large mouthful.

Good luck!
Tom Krajci