Mirror making: some joy some rage

The mirror I am making for my telescope is almost done. But it is the last mile which is the most trying.

I am in the polishing stages of the mirror and two events happened today:

First the good news. Looks like the focal length of my mirror is much lesser than I had believed until now. It seems to be about 68 to 72 inches, instead of the 85 inches I thought it was.

Which means my scope's length will probably be a whole feet shorter, which is great!

The bad news is, I did a round of polishing yesterday night which has caused scratches to appear on the mirror. There are 3 of them. Not too deep; but gives me jitters. Either my workspace is too dusty, or the polishing agent is contaminated.

I can't take a risk now. So, I will stop using this polishing agent and wait for a new batch to arrive.

More good news. I just built a Focault tester, and my mirror appears to be perfectly spherical!! Woohooo!

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