Re: [ATM] convex side

["Donald Good" <donald.good@comcast.net>]

You stated in a previous post that it is an optically true concave mirror.
Here you add that the reflective coating is like a household mirror which is
also called a back surface mirror.  A back surface concave mirror made from
ordinary glass is commonly used as a makeup mirror or shaving mirror, but
they are not optically true.

You don't say where the mirror is from, but if you have an optically true
mirror, it is possible that it is from an optical instrument that uses the
back surface reflective coating as part of the optical design.  If this is
the case, the glass is optical glass acting as a lens and probably has
anti-reflective coating on the front side and the edge thickness would
likely be different from the center thickness.

Don

> -----Original Message-----
> From: atm-bounces@atmlist.net 
> [mailto:atm-bounces@atmlist.net] On Behalf Of Saqib Sajjad
> Sent: Monday, October 17, 2005 9:14 AM
> To: atm@atmlist.net
> Subject: [ATM] convex side
> 
> hello everyone,
> 
> 
> after a week of absence i am back.i am about to start work on 
> my 4" telescope.a small problem in my mirror which was 
> pointed to me by mahmood when we met(a day before the 
> quake).my mirror has convex side coated like a house hold 
> mirror such that i get the image when i look at the concave 
> side.mahmood pointed out that concave side should be 
> coated.so can anyone tell me is this mirror worth making the 
> telescope or is it piece of junk too?
> 
> 
> Saqib
> 
> 
> 
> 	
> 		
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