Re: ATM Help, Please: Losing Ground

[Bill Marriott <btk@pacbell.net>]

Doug B wrote:
> 
> 1/4D W strokes are supposed to produce a sphere, right?
> I switched to this after 5 hours of brute force 1/3 ToT CoC polishing, which
> had produced a reasonable sphere, with a TDE. 

Doug:

My .02

In general, I recommend dealing with the two issues separately.

1st - TDE  If minimal, I would use MOT, with a 1/3rd stroke, (remember
to divide between front and back). If the TDE is a major  problem, we
have had good success with TOT with a 1/3rd stroke, shortening to 1/4 as
it reduces, and then flipping over to MOT at the end. If you  do TOT for
too long, it can knock the edge back down. If your lap is in good shape,
and you rotate everything properly, it will go away. We have had great
success at the Chabot telescope workshop with these methods.

Once the TDE is gone, then deal with getting your mirror spherical, with
combination of 1/3 center over center MOT, with some parabolizing W
strokes to reduce the oblateness.

Good luck

Bill
--
Bill Marriott
http://www.starlightoptical.com
telescope/optical stuff