Re: ATM 8" mirror questions - weight, good sources, mirror cells?

["John A. Volk" <103037.3107@compuserve.com>]

<1) How much is a "standard" 8-inch mirror going to weigh? I am trying to
calculate balance points, etc and am having problems because all weight
info in the AstroSystems book are for 12.5" and up scopes. > 

- 5.5 lbs. for an 8" f/7  with standard thickness (1/6th the diameter, 1.33")

The general formula is as follows:

D = mirror diameter
rho = density of material (.0838 lb/in**3 for Pyrex)
T = thickness of mirror
Pi = 3.14159....
S = sagitta or depth of mirror
f = f# of mirror

first  S = D/(16 x f)

Weight = density x (volume of flat mirror blank - volume of material removed*)

* assumes sperical surface - weight removed to parabolize sphere is negligible


Weight = rho x ((Pi x D**2/4 x T) - (Pi x S/2 x (D**2/4 + S**2)))


John A. Volk