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Re: [ATM] Astigmatism and Ronchi questions

> So here is the deal ..

BIG SNIP OF THE BABLE

> 5.)  Could this just be a sag / mounting issue?

I can answer this part now.  Yes, the effect is brought about by sag of
the glass.  I placed the tube on end looking up.  I then got on a table
and with a stick for support and control I looked down the tube with an 85
line tester. I saw a nice clean transition from inside to outside ROC and
back.  I ran it several times to be sure I was not fooling myself.  I will
see if I can get a photo or two of the thing.

>
> 6.)  Why is the error only seen with finer grids?

I suppose the effect is so small that the 50 line cannot catch it.  The 85
line only shows one of twist.  I have a 130 line grid here, I should see
what it looks like through that.

 David Davis
 Toledo, OR
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