Re: [ATM] reworking 12 inch

["Rod Brackenridge" <rjbr@gawab.com>]

Hi Paul,

Sorry to hear about the accident with your mirror - sounds
awful!

>From what uou are saying about the lack of progress figuring I
am wondering about the following:

Is the lap glazed?  Mine became that way and was very
inefficient.  Microfaceting fixed the problem.

Is the lap too hard?

What kind of stroke are you using and what is the focal length
of your mirror?  I have never mastered full sized laps on fast
mirrors.  I prefer sub diameter laps. If you have the Krieg and
Berry Book, there is a good section in the back on using sub
diameter laps for parabolising.

For me, contact should feel smooth rather than resistant.

Hope that helps,

Rod.



Paul Foreman writes:

> last summer my secondary fell off and smashed on my primary, gouged and scratched it.
> I've been figuring it for about 10 hours (of figuring-not counting pressing,testing etc.) and I'm getting very little parabolization effect
> I've rechannelled the lap 3 times just in the parabolization  mode.
> I'ts been several years since I first  made this mirror and  I don't remember.
> I know the archives say to push with just enough pressure to move the glass.
> But I sometimes, just like when polishing it moves easily and sometimes takes lots of effort to move it.
> Do I want to parabolize it when its very difficult to push the mirror or should it slide fairly easily
> Thanks
> Paul
> _______________________________________________
> ATM mailing list http://www.atmlist.net/

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