This blog is mainly about Telescope making, and some things about my politics. At last we finally have a President that can say "Fool me once; shame on you. Fool me twice; shame on me." instead of mixing up with an old Who song.

Thursday, October 16, 2008



I turned the edge of my mirror. I got over anxious and went too long and hard with parabolization. It gouged a hole in the middle and turned the edge. And while I made significant progress towards making the center and other zones pretty close to 1/4 wave P-V, I was never going to be able to fix that turned edge and keep the paraboloid.

So I polished out the edge, center be damned. Now the center is slightly raised, but overall its a sphere. Slow 30 per minute 1/3 W strokes. Six one way six back 4 times in one place. turn the mirror 90 deg CW, turn around the barrel 45 deg, do it again - around the barrel twice that way. Finally, no turned edge... I think.

Here are pictures, let me know.

What appears to be a flat center sloping up at the edge. Click for a bigger image and you can see perhaps there is a darker shadow on the right, but no matching bright ring on the left (KE is positioned on the right)

Here is a ronchigram. It's made from a transparency that I reduced down on a copier at Kinkos. 40 lpi. This is inside focus.

This is further inside focus

This is outside focus.

I'm not seeing the tell tale curls at the ends of the lines indicating a turned edge anymore. I sure hope I got it licked.