What are those circle shapes? | Hacker News

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		miningold on Nov 23, 2014 \| parent \| context \| favorite \| on: Schlieren Optics – See small changes in the index ... What are those circle shapes?

amritamaz on Nov 23, 2014 [–]

I think they are aberrations in the mirror's glass. People used to use Schlieren optics-esque techniques to test glass for defects.

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