Re: ATM potato chip mirror

[Bill Marriott <btk@pacbell.net>]

ToobWiz@aol.com wrote:
> 
> Frank,
> 
> It seems that all my Ronchi tests turn into ying-yang figures and then flip
> while going through ROC. I've thought that was appropriate !!!
> 
> All I've concerned myself with is the images inside and out. The mirrors seem
> to work OK :-)
> 
> If you get responses saying different, I guess I'm in trouble.
> 
> Cheers/Carron

Hi folks;

When over at the Chabot telescope making workshop, when I ask Paul
Zurakowski (the director) to really give the eagle eye to one of my
mirrors, if the Ronchi fringes do flip going through ROC, then Paul
calls it saddle astigmatism. If it is minor, he doesn't even mention it
to our regular clientel. Now, as to what level we are talking
about,we're not sure, will it be detected visually, probably not,
startesting? maybe so, but with 30 plus years testing mirrors, if Paul
calls one of my mirrors astic, then I have to go with his opinion, and I
have found that if everything is done right, the yan/ying thing does not
show.

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