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5-micron Alox Stubborn

Started by brucesdad13, 08/16/2015 09:43PM
Posted 08/16/2015 09:43PM Opening Post
My first mirror is coming along. I'm using an 8" Pyrex blank full thickness and an 8" plate glass tool. Tonight I made it down to 12 micron and finally started with 5 micron. I'm having issues with the two wanting to lock together when I work the air bubbles off the edge. I have found that rapidly moving whatever is on-top and only sliding bubbles off the edge when using a center-over-center motion that I don't feel it begin to seize. Thankfully I've always been able to prevent them from locking together. I'm using a wee bit of soap and that seems to help. Any other suggestions??

~ Charlie Stevenson

8" f/5.7 String Telescope - 1st Scope Build; 2nd Place Stellafane 2016 Optical Award for Newtonians 12.5" and Smaller
10" f/4.5 Newtonian (June 2015) mirror refigured by Optic Wave Labs P-V WaveFront 1/14.24, Strehl Ratio 0.993 (Aug '15)
Criterion RV-6 seems to be circa 1973 (June 2015) [For Sale]
Celestron C8-A XLT (January 2015) [For Sale]
Celestron PowerSeeker 70AZ (Christmas 2014)
Aldrich Astronomical Society member since 2015
http://astro.charleskelleystevenson.com/
Posted 08/17/2015 05:22AM #1
That is a common problem at the finest abrasive. Keep it pretty wet. If the bubbles prefer to stay near the center that would be a depression in the mirror there and it acts just like a big stiff suction cup when it hits center-over-center in the stroke. Quick fix to that is short c/c strokes. When both are good matched spheres, the bubbles have no preference and are real little and evenly distributed (and harmless). You can really tell a lot about the shape of the mirror just on how the bubbles behave. Tom

29-inch Dob in a dome
36-inch upgrade soon
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