Re: [Re: ATM Polishing/Figuring questions]

[Doug B <dougbr@usa.net>]

w2vy@xanthus.net wrote:
> Doug,
> 
> Don't confuse a TDE for an UPE (UnPolished Edge)
> 
> Look very closely at the edge, it might not be done yet...
> 
> Maybe you need to Polish More and worry less...
> 
> I am sure others will correct me if I am wrong...
> 
> Tom Moulton
> w2vy@xanthus.net

Tom, 

Thanks for the response. 

I'm pretty sure this is not a case of the edge receiving less polish, I did
TOT for the 1st 5 hours of polishing, I could actually feel that the lap was
doing work on the edge, at some points the edge would start digging ito the
lap and i would have to re-press. There is no difference in the reflection of
a laser beam between the edge and center, and no visible pits or haze through
a 10x loupe. the laser beam reflection is much dimmer on the mirror than on
any of my binocular or camera lenses. also, switching to MOT did reduce the
width of the TDE by about 1/2, while at the same time deepening the center.
However, there is a narrow part of the edge that is not receiving much
polishing action with MOT and it looks just about as wide as the TDE that i
see in the Ronchi test. 
I'm wondering if parabolizing might bring the outer zone of the mirror down
enough to get rid of the TDE. 

> >My 8" looked pretty much polished out after ~ 5 hours, so I checked the
figure
> >with a quick look through my (not yet completed) ronchi tester. Looked
> >spherical, with a bad TDE. I've been working TOT, 1/3 COC stroke for the 5
> >hours of polishing, so i figured the TDE must have come from the edge
getting
> >too much polishing action. I switched to MOT 1/4 COC stroke for another 2
> >hours of much gentler polishing. TDE now looks better (narrower) but i no
> >longer have a sphere. it looks like i'm making the center deeper, bands
curve
> >inward inside CoC and outward outside CoC. should i continue MOT until i'm
> >back to a sphere, or should I go back to TOT to bring the the edge down to
> >meet the curve of the center. or should i finish building my Foucault
tester
> >and attempt to parabolize from this point and hope the edge comes down
enough
> >in the process to get rid of the TDE? 
> >
> >____________________________________________________________________
> >Get free email and a permanent address at http://www.netaddress.com/?N=1


____________________________________________________________________
Get free email and a permanent address at http://www.netaddress.com/?N=1