Astrophotography forum > ATM, Optics and DIY Forum

does polishing glass fill pits?

(1/3) > >>

does polishing glass fill pits or does the glass wear down to the bottom of them? I wonder because there are pin hole size pits that might be deep and polish out slowly on my mirror. I did about 10 hours polishing and still have pits. The ruler is 1/64" lines. The pits are 120 microns across.Attached Thumbnails

Jessie Forbes:
Yes it does. Eventually. The quality of the area where pits are filled isn't quite as good and causes problems for UV transmission systems because impurities in the silica deposits from the slurry get captured into the fill. High energy laser mirrors will also fail at these points, so there's a whole tech method devoted to avoiding such problems.

Is your entire surface like this? That's too many pits, you need to return to fine grind to remove them.

Must be 100 pits / square inchat the edge. The middle about 10 pits / square inch.  Left over from rough grinding probably. It sounds bad but the glass looks all polished to the edge.

It's not polished out if there are pits remaining from fine grinding. You need to go back to fine grinding! Estimate the size of the largest pits and start one grit smaller. Trust me I understand that this is disappointing news! You have undoubtedly put a tremendous amount of time and effort into your mirror. Don't waist that investment. Take the time to make it right, even if you put a decent figure on the mirror it will still perform poorly. You'll be disappointed with the performance and have waisted your time and effort.
Just my opinion. I struggled with the same decision! In the end I was fortunate to have listened to the advice given by many of the very experienced mirror makes here and ended up with a mirror far beyond my expectations and certainly much better in quality than anything I could afford to buy!


[0] Message Index

[#] Next page

Go to full version