14" OTAs - weight

Thanks for the piece of info.
I guess this is good and bad,

Good in the sense that the meade mirror is probably more rigid due to been thicker, less chance of warping.

Bad in that due to the extra mass, its cooling down time would be lengthened.

I doubt very much that the celestron mirror warps, and if your in an permanent setup then the cooling down factor of the meade mirror is not really an issue.
I wonder why meade choose such a thick mirror?

I have always been led to believe that the thinner the mirror, the better. Thinner means less mass for expansion, which means less 'warped' images when changed from a warm to cold environment. Obviously, that also means less waiting time for the instrument to adapt to the new environment.

Seanie,

It all depends on how the mirror is supported. In a newtonian, the weight of the mirror is supported by a mirror cell, which is a system of support points underneath the scope.

In at least some SCTs if not all SCTS, there is no support mirror cell - it is the thickness, shape and strength of the glass that holds the mirror in one piece and prevents it from deforming. In this case, the thinner the mirror, the more it will deform.

The only question remains: how thin can you make the mirror before the deformations become a problem?

Regards,

The only question remains: how thin can you make the mirror before the deformations become a problem?

That, of course, will depend on the diameter of your primary. There is no defacto I'd imagine, but factors to take in would include mirror thickness versus diameter versus weight of the glass (and its make up) being used.

And glass is not glass with telescope mirrors - there is plate, suprax, pyrex, BVC (black vitreous ceramic), borofloat, and a couple more.

Another one is fused silica, which I have heard has almost the lowest (co-efficient of thermal) expansion. But most mirrors are made from suprax or pyrex.

S.