Re: ATM Are We There Yet?

["Dwight K. Elvey" <dwightk.elvey@amd.com>]

>From: "Mark Holm" <mdholm@telerama.com>
>
>
>> and entered the resulting 4431.7856mm in
>> Sixtests as both the Source Distance and the Knife Edge Distance.
>> 
>
>
>
>You seem to have a moving source tester.  So far as I can tell, it isn't possible
>
>to make a slitless one that isn't. 
---snip---

Hi
 I don't know why a slitless can't have a fixed source.
You are assuming that one must always use the same edge
in a slitless. On my machine, I've mounted the source
edge in front ( about an inch ) of the resolving edge.
This was because I didn't like the LED in my cheek.
Before I had tape on it, I'd get a small electric tingle
from sweat on my cheek. When I insulated it, I could
still feel the heat from it. It bothered me so I
mounted a separate edge ( I could have even made this
a fixed source ). One just needs to be able to make
fine adjustments to the angles of the edges. It would
cause problems on a vary fast mirror but I don't expect
to measure anything below a F/4. The distance from the
mirror to half way between the two isn't exact either
but it is closer than the other errors of the system
for long focal lengths. For the most part, it makes
no difference and works just as well. Even if used on
a faster mirror, one could easily make a spread sheet
to do any small corrections.
Dwight