[ATM] ATM: Slit equipped and slitless testers-

["David Harbour" <stainless_steel@suddenlink.net>]

Gary, Roman-

Only two thought it worth while to check in. You both voted with me. So, 
here it is for you guys: (not that it matters; anyone who needs math may 
skip this windy dissertation)-

If, when one arranges the knife edge on his or her tester, so that it is 
simultaneously one side of the jaw of the slit (this is easily accomplished 
by merely staggering two razor blades, lengthwise, vertically, by half their 
length, each one) then, even though one has a slit behind which to place his 
or her favorite kind of illumation source, the slit equipped tester also 
operates, automatically, every time the KE is advanced in from the side, 
laterally, as a SLITLESS tester.

That is the conclusion I reached after I tested dozens and dozens, and yet 
dozens, of mirrors, and never missed a flaw, even a tiny one, when my slit 
was pronounced as way too wide. So that is the conclusion I reached. Even 
though  the slit was very wide (.010") it functioned better than my best 
expectations; so I reasoned about it, and that is the answer I came up with. 
The other jaw is useless. I think Ralph Dakin broke ground on this theory 
and practice. To me, it is this way: the first side of the aerial image of 
the slit that the KE encounters, is its own (in reversed image)- it has no 
idea (razor blades cannot think, sometimes do not shave well either, but as 
Ralph found out, can still cut a hand very badly, if not epoxied on the back 
side of a plate with two ports in it) where the other edge is, or how far 
away it is. It could be light years away, for all the effect it has.

But, you both said I am right about the reflections. That is why you see so 
many photographs of astronomers looking (not amateurs) through an eyeiece of 
the Cassegrain focus of a large Cass, without a diagonal, and looking 
through a large refractor, same way- straight through. Zero reflections with 
the refractor; even numbered with the Cassegrain. Thus, one sees the moon, 
for instance, more normally; much closer to "map reading" correct, than when 
one views it as everyone does who has a Schmidt Cass- with a diagonal; in 
that case, it is mirror reversed.

I was out at our way, way, way over-equipped observatory here at Northern 
Oklahoma College (amount of telescopes, 16 ft ash dome, and piers and mounts 
for scopes, above what the law allows- my heliostat, which universities are 
all asking for detailed drawings of, and now- an $80,000.00 planetarium, 
under construction; 50 foot geodesic outside dome; very impressive). They 
have waited, so far, over a week to get the structure bolted down; hope it 
does not become the nose of a great airship, to speak metaphorically, on a 
short flight onto someone's front porch to the north.

While I was out there, I saw that beautiful, gigantic photographic atlas of 
the moon- the one that was "rectified" by projecting the images onto a white 
sphere, and rephotographing them. I forget the exact name of the atlas; but 
I noticed the Kuiper's name is on it; what is interesting is that contrary 
to normal useage, north and east on the pages is "earthlike" (from the 
perspective of someone standing on the moon, breathing vacuum, and trying to 
get a reading on his or her compass). I did not know that this convention 
had been adopted; it is contrary to astronomical useage. As for instance, in 
my classic book by Moore and Wilkins, "The Moon"- a slightly rare book in 
which is a catalogue of about 3,000 named objects, short bio on who they 
were each named after, and often a drawing or photograph, and then 
considerable description- Moore and Wilkins made most of these observations 
with the Meudon 33" refractor.

The book has Wilkins' 300 inch diameter map in it.

Fingers are tired.

R-101 


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