[ATM] Polishing questions - stop polishing, keep polishing, or go back to fine grinding?

["David Steinhauer" <desteinhauer@verizon.net>]

I have some questions regarding my 6" f/5 mirror.  I have spent 12 hours so far polishing it.  According to all 
the books I have it should have been done several hours ago.  But, according to some tests it still is not.

- It looks as clear as can be to the eye, even when shining a flashlight on it.
- When focusing sunlight or light from a bright flashlight on the top mirror surface with a 1" diameter lens it is 
pretty easy to see scattered light from the spot where the light hits the top surface of the mirror.  The 
brightness of the scattered light is the same at the center and edge of the mirror - I can't see any variation at 
all.  I have noticed no change for at least the last four hours of polishing.
- The other day I bought a $10,  60x illuminated microscope from Radio Shack.  Looking at the mirror 
surface, I can't see anything but an occasional speck of dust.
- However, when I look through the 60x microscope while illuminating the mirror by focusing sunlight on the 
surface with my 1" lens, I see hundreds of bright tiny spots!  I'm pretty certain these are pits.

According to Texereau (Fig. 2-20 on p. 54) having close to 100 tiny pits per square millimeter is a "normal" 
polish.  He also mentions such a thing as has happened to me, where a mirror never really polishes out (p. 
53).  He doesn't explain the root cause, though.

So, did I not spend enough time in fine grinding?  I did 16 wets of 15 micron grit, and 18 wets of 25 micron 
grit.  After each grit I inspected the surface with the 1" lens, although I admit that the magnification probably 
wasn't high enough to really allow an effective inspection for the last couple of grits.

Should I go back to fine grinding, or accept that the pits on the mirror are probably no worse than the amount 
of dust that typically will reside on the mirror surface?  Or is this something that might polish out with a few 
more hours of work?

Thanks in advance.

David Steinhauer
Lynnwood, WA, USA

P.S. If you're interested, here's a few words about my background.  Twenty-one years ago when I was 12 I 
tried to grind a 6" f/8 and eventually gave up (I was trying to rough out the curve with a standard center-over-
center stroke.  Needless to say, it took forever!).  I finally bought Richard Berry's book Build Your Own 
Telescope when the first edition came out, and built the 6" German equatorial, using commercial optics.  
They must have thought I was a bit odd building the pier for the mount in eighth grade shop class.  I took a 
break from astronomy for many years (college, married, had three children - no energy for hobbies with a 
baby in the house), but now I'm back, and enjoying amateur astronomy more than ever.
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