[ATM] TDE, Ronchi, Knife edge

[bobmay at nethere.com (Bob May)]

Sounds like you are gradually taking down the TDE by the expedient of
digging deeper into the glass at all points.  In other words,  your ROC is
staying the same but you are removing glass to get rid of the TDE.
The knife edge in the slitless testers is normally the same edge for cutting
the light source as well as the returned image.  You don't need to have the
two parts of the edge the same (the slit tester works this way with the
fixed light sourece) but the angle has to be 0deg. in rotation between the
two edges or you will see apparent astigmatism in the image of the mirror
with the shadows sweeping down or up as you block the light returning.
Hope that this is what you were talking about.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
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