Re: [ATM] Ronchi test accuracy

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I don't claim ANY numerical accuracy whatsoever  for the Ronchi test. What I *DO* claim is that the Ronchi test is a  very fast and convenient method that you can use to check the overall  figure. If if looks bad under Ronchi, then there is no need to do any  zonal Couder-Foucault measurements or any other numerical/quantitative  test whatsoever. A quick Ronchiscan can tell you what parts of the  mirror need to be worked on, in a jiffy (not really 1/60th of a second,  maybe it will take you 5 to 10 seconds). Now, if your mirror looks good  under ROnchi, then it's time to begin running numbers with a couder  mask (or whatever). And I find running the numbers can take nearly an  hour if you do it right, repeatedly, and on 2 or more diameters.
  
  Ronchigrams save a *tremendous* amount of time, in my opinion.
  Guy

Mike Lockwood <melockwo@uiuc.edu> wrote:  Guy,

Guy Brandenburg wrote:
> Another problem with Texereau - he completely neglects the Ronchi
> test.  So do the LeCleires.

And so do I!  ;)   (This may be unfortunate for me!)

> I think it's important to supplement any given book with newer
> stuff from the web. One web resource I haven't seen mentioned yet
> is Peter John Smith's comparative ronchi testing pages. Also
> RonWin.

Seriously now, has anyone ever attached a figure to the accuracy
limits of these tests, that is, any type of new or old Ronchi test?

Maybe Mel can chime in here.

It's routine for me to confidently take Foucault testing to 1/10th 
wave wavefront error (confirmed by later star testing).

How far can Ronchi (by itself) go?

 Mike Lockwood





Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
_______________________________________________
ATM mailing list http://www.atmlist.net/