Re: [ATM] Figuring question

["Jerry" <wa4guu@verizon.net>]

Ten zones is too many. Even if it is two 5 zone masks. I don't think you
should mix the readings of two masks as you have. When I break out the
numbers into two 5 zone readings there is a pattern of result that suggests
up and down slopes in the 10 zone readings might not be real but by a
misplacement of the overlay of the two 5 zone readings.

I would suggest as Mike suggested, a 7 zone mask would be enough.
Or use the 5 zone readings as stand alone tests instead of blending them.
You will probably (should) see that the results of the 5 zones will be the
same generally as the 10 zones. Use the Ronchi test to see exactly where
slopes change.

Basically you are overcorrected in the center and under corrected on the
outer 40%. I won't say what I would do because I would test with one mask
and also with Ronchi to decide exactly what I would do. And it would be to
danged complicated anyway.

Jerry

-----Original Message-----
From: lance clarke
 
Thanks Mike,
I really appreciate the advice, especially how to better use figure XP.
Also, just to let you know, I'm not using a 10 zone mask, I'm using 2 
alternating 5-zone masks.  I find that even with 5 zones it can be hard to 
judge the very outside zone due to diffraction.  I think my next upgrade to 
my tester is to rig up a finderscope or something else low power, in order 
to judge the outside zones better.

Thanks again,
Lance

>
>10 zones for a 12.5" mirror is a bit high.  If you really want some testing

>practice and you want to check your skills, try a 7-zone mask.  But, 
>assuming the readings are OK, you should first worry about the outer zones.
>etc.....


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