Re: [ATM] my ongoing war story (polishing and figuring)

["Vladimir Galogaza" <vladimir.galogaza@zg.htnet.hr>]

Rodney,
To my question:
 >Which feature of Ronchi image you found was telling about mild
astigmatism?

 the answer was:
>The unusual curves near the ends of the bands (top and bottom),

Basically they tell most about edge condition (TDE).
But you mentioned:

>I have seen on the web of ronchi images where experienced
>persons have determined the existence of astigmatism.

"experienced" you said.  If you saw those minute details that you must also
be
equally experienced and in other parts of your post you said you are not.
I think that there is no way to follow blindly the path of some experience
people advices
without being able to justify them when you apply them.
 But you can do that only if you are experienced and all this is simple case
of catch 22.

Therefore instead of using Ronchi, you will climb the learning curve more
effectively
by using Foucault test. It will give you more insight on what are
consequences
of particular actions (if used often) and since it is quantitative, how far
you came.

There is almost no difference in construction of Ronchi and Foucault tester,
so if you
are already doing Ronchi you can switch to Foucault and use one of several
free data
reduction computer programs. Another advantage will be that you can present
to list
some mirror figures for discussion which will tell more than verbal
description.

>But, I was concerned enough to stop and go back to sphere.

No need for this unless you know that such a step is more economical than
improving the figure you have. And again, you will know it better by having
Foucault data on hand.

Regards
Vladimir.




-- 
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.375 / Virus Database: 267.15.9/261 - Release Date: 15.2.2006

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