Re: [ATM] Foucault images

[Mike Lockwood <melockwo@uiuc.edu>]

Dale,

Dale Eason wrote:
> I can't seem to match the number of lines with a 133
> screen using my simulator.  However I can get the same
> kink in the middle using 38 waves PV on the Surface.
> http://www.atmlist.net/contrib/atmpob-at-yahoo-dot-com/38waves.jpg
> There may be other combinations but I used 133 LPI
> -.05 inch offset and perfect correction.

Let me double check to make sure it was a 133 LPI grating.  I have 
several, but I thought that was the one I was using.

> What I think is the diffraction from the dirt will be
> aligned with the knife.  Somehow there is evenly
> spaced obstructions in your setup that could be
> creating the lines.  I don't know enough about it but
> could it be the spacing of the CCD showing up?  Maybe
> there is a fine pattern etched into the coating of the
> CCD cover plate.
> 
> I think these tend to vanish as the slit is made
> wider.  You could try that to see if they diminish.
> Then you would know if they are related to diffration.

All right, I will double check the grating frequency tonight, as well 
as try taking some Foucault images with the camera tilted to see if 
the vertical pattern tilts with the camera.

When I get a chance, I will also try limiting the vertical size of the 
slit as John Sherman suggested, to see if that reduces it too.

I will also VERY carefully clean the eyepiece and objective.

Thanks for all the astigmatism estimates so far!

	Mike Lockwood

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