[ATM] Amount of Under Correction??

["Peter" <peter@kitgear.com>]

Hi,

I'm working on a 16" f/4.5 2" thick Pyrex mirror (full thickness) and it
currently has a very smooth figure, great edge so I'm getting close.
I was told that fast thick mirrors should be under correction to compensate
for the cool down throughout the night. I'm currently at 85% correction
(just over 1/3 wave front).

I wanted to ask it this is true that I should under correct the mirror and
by how much?

Thanks for your advice.


Peter

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