Quote:
Originally Posted by sunslayr
The original newtonians used a metal mirror I can only imagine that a 20" aluminium mirror would be much lighter than a glass one. If the mirror was large enough it could compensate for any reduction in reflectivity from a poorer surface finish, not to mention aluminium is much faster to grind and shape than glass. The last idea I had was that stuff they sell at bunnings called Rust-Oleum Mirror Effect spray.
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Hi there, sunslayr,
some interesting ideas there!
I am not sure if an Aluminium primary mirror would yield much of a weight advantage over a pyrex mirror, but I think the general principle that you have outlined of trying to find a lower density material from which to make the primary mirror, is worthy of following up and investigating. Every little bit of weight saving is a good thing, in telescope design.
Here's an interesting thread on alternative mirror materials:'
https://www.cloudynights.com/topic/408925-metal-aluminium-primary-mirror-making/'
Here is a table of the comparative density of various solids:::
https://www.engineeringtoolbox.com/d...ds-d_1265.html
( I hope it is more correct than a lot of that suspect info on the web!)