Re: [ATM] TDE on a 6f6 mirror

[Mike Lockwood <melockwo@uiuc.edu>]

Anthony,

Anthony Anconetani wrote:
> Mike,
> You mentioned astigmatism. Looking at the picture zone2_crop.JPG is
> lumpyness causing the astigmatism? Or do you see a bigger problem?

I think it was air currents.  The lumpiness makes it hard to detect 
smaller amounts of pure astigmatism with Foucault.  I don't see it 
now, but that does not prove that the mirror is a figure of revolution.

The problems I see are surface roughness and an outer ZONE that is 
rolled (as well as the edge).  Your knife is still shading it on the 
right side even though you got it mostly out of the way (but not quite 
all the way), so that roll seems to be fairly severe.

> What's the difference between a "rolled edge" and a "turn down edge"?

They're the same.

Earlier I said "rolled outer zone", not "rolled edge", and to me that 
means the outer ZONE focuses too long.

A ZONE has significant width, more than 1/16", while the edge of the 
mirror is literally the edge, and is very, very narrow, let's say 
1/32" wide or less.  It is the condition of the edge that forms or 
does not form the diffraction ring around the mirror.

> Lastly, yeah blue LEDs... Too Cool...  I got that idea from some guy
> up in Illinois. 8-) Actually, I saw them in DigiKey and couldn't
> resist.

About this time someone will ask if the blue LED provides more 
accurate test results because the wavelength is shorter, and of course 
the answer is no because the accuracy depends on the geometric 
placement of the knife edge.

	Mike Lockwood


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