Re: [ATM] How should I finish polishing this 8" F/6?

[Mike Lockwood <melockwo@uiuc.edu>]

David,

davidtrumble@comcast.net wrote:
> I'm hoping to get some advice on how to finish polishing this.
> Please take a look at:
> www.atmlist.net/contrib/davidtrumble-at-comcast-dot-net/06-06-22%20Dave/
> Some details: 8" F/6, 100 lpi Max Levy Ronchi grating.
> I've been trying slow, short MOT, COC strokes

Are you polished out?  Even the outer zone?  Check polish over the 
entire mirror's surface carefully.

How long do the channels in your lap take to close when you are doing 
normal polishing?

If you are NOT done polishing (<8 hrs. work) then I encourage you to 
work TOT, normal strokes until you are polished out.

If you ARE polished out (and have verified this with a laser, strong 
light/loupe, or by another accepted method).....

At first glance, this looks like a classic oblate sphere, assuming the 
knife edge comes in from the left (the photo may be reversed).  The 
oblate is often accompanied by a turned edge.

Here's my page on fixing oblate spheres:
http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/oblate/oblate.html

The ronchi image indicates that your rolled edge is more severe than 
most I have seen, and it will take a while to eliminate.

I think I would recommend working TOT to fix this, as I describe on my 
page.  You will want to press the lap every 15-30 mins.  It's going to 
take a while to fix this, since the roll is significant.

Mike Lockwood
http://bi-staff.beckman.uiuc.edu/~melockwo/index.html

_______________________________________________
ATM mailing list http://www.atmlist.net/