Re: [ATM] newbie question

[Mark Holm <mdholm@telerama.com>]

There are previous discussions in the archive, but since we don't use 
standardized phrases to refer to things, searching isn't always productive.

Aluminum metal as a mirror substrate has a number of problems, and some 
of it's supposed advantages turn out not to be.  A couple of examples 
follow.

1. The ability to put mechanical features on the back or side of an 
aluminum mirror is illusory.  Sure you can put them there, but the load 
distribution won't be anywhere near good enough for any but the smallest 
mirrors.

2. Which would you rather do when the aluminum surface gets cloudy after 
a few years of exposure to the atmosphere?
	a. Repolish and refigure the aluminum mirror.
	b. Wash off the old aluminum from a glass mirror with a bit of
	chemical, leaving a still polished and figured glass surface
	ready for recoating?


-- 
Mark Holm
mdholm@telerama.com

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