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Hello,
Normally you just turn a 25mm plossl around and look at the glass close up in a strong light for the 1st few grades. After that a 10mm reversed around for your seeing glass, but that may just be because most ppl have those ep's.
Its about seeing the same size imperfections across the mirror to know that your done with a grit. Also check to see that the center, middle and edge are all progressing together evenly. You should see no variation in the surface finish from edge to center, neither smoother or rougher in any zones.
I'm still on my first mirror and can only say I can see the difference between 750 and 1100 under a 25mm plossl seeing glass(24-16micron) with fairly old eyes.
Steve
Ps. You generally grind at half the grit size, so, the 750/1100 is going from 12-8micron smoothed surface.
Last edited by mura_gadi; 10-08-2021 at 04:53 PM.
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