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Old 30-01-2010, 08:17 PM
Bern
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Bern is offline
 
Join Date: Jan 2010
Location: Sydney
Posts: 6
ATM-optics query

Hello everyone, this is my first post, and I am impressed by the amount of information and knowledge available here. Do people still hand grind their own mirrors, or is this a dying art? My late father made several telescopes in the 1960s and '70s, mainly Newtonians and a casegrain. The primary mirrors varied in size from 4.5 inches to 8 inches. In the final stages of polishing he would assess the accuracy of the optics and focal length using various methods, such as straight-edge and grid tests, I think. He used different hand-polishing manoeuvres to correct optical deficiencies. I recall him referring to turned-down edges and turned-up edges among other things. He never had much time for commercially made or machine-ground mirrors because he felt they weren't up to standard or were just too expensive because of the enormous amount of labour required to make them. So how does the optical quality of current commercially made mirrors compare with hand-made ones? I would imagine mirror manufacturing technology has improved vastly since my father's time, but is a good hand-grind-polish job still regarded as superior to a commercial job? If not, how do you independently assess optical flaws in a commercial mirror before purchasing it? Also is there much optical variation within identical telescope models? Thanks for taking the time to read the post.

Bern
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