Re: ATM A wee problem with correctors

[Bratislav Curcic <epabcc@epa.ericsson.se>]

Dave wrote :

> corrector plate will be
> undercorrected for my optical system by about 6% 

> I have several courses of action available:

> 1) While the corrector is still sitting on the vacuum pan I can pull more
> vacuum to deflect the plate to the (expected) correct center deflection and
> then (1a) try to polish a new sphere into it, or (1b) go back to 20 micron
> grit and grind the new sphere into it and re-polish the darned thing. 
> ... corrector go about 40 microinches aspherical (about 1 micron).

The speed of polishing for Crown is about 2 microns per hour, using CeO2.
Nothing to worry.

 > (1a) worries me.  How do I know when I have polished back to spherical?

The lap will grab like velcro with asphericity. You may need to go easy
and start by hand initially. Lotsa cold/warm pressing will be
required.  When you get lap to glide over the corrector again you can
be pretty sure that you have decent sphere. Final touches you can do on
the corrector using small star lap (~1"). It will make corrector rough,
but you won't see it on film.

Whatever you do, don't touch the mirrors. All action has to happen on the 
corrector if you want to use that 6 by 6 cm film.

> 3) Use the corrector as-is as a cheese dish.  The figure is no longer that
> important.  The cored 10" f/2.2 primary could make a very interesting candle
> holder.  Imagine the play of light on the ceiling if I got it aluminized.

Now, THAT'S what I call radical idea ...

Bratislav