The Skywatcher quality control on these is "1/4 wave". See my last blog post for some pretty fine detail in M81 that I caught with mine on a cold but very stable night. I've only looked through an 18" Hubble at low-medium power; not much of a test. Good luck with your project.
Last edited by Ivan Maly; January 12th, 2018 at 01:10 AM.
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