Re: ATM ? post

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

Todd,

you don't tell whether the KE problem occurred in a "Foucault-like" situation. I haven't 
tried but here's what I would expect from a cylindric "knife-edge":
Light from one side A would be intercepted a little nearer the mirror, the other side B a 
little farther (and closer to the zonal COC). This would balance at the true distance, 
but the A side aperture would have a little more brightness gradient across the zone than 
side B, and they would be a little harder to compare than with a more normal KE. Using a 
cylinder of just a few millimeters dia. would not likely affect the readings much, but on 
the other hand I can't think of a problem it would solve (other than the nose-cutting 
effect).

The main requirement is that the "knife" edge is straight without being jagged, and that 
the same edge intercepts the light from both sides - it does not have to be "sharp" at 
all.

Nils Olof