Re: [ATM] More on my Mak-Cass project

[Andy Saulietis <iss@pvtnetworks.net>]

Re knife edge baffles,

It's a good idea to try to minimize the number of baffle
edges as seen from the image plane..the idea behind baffles is to
make the incoming stray light bounce twice before reaching the
focal plane. The knife edge itself bounces the light once, therefore it's total
area should be as small as possible, and the knife edges as
sharp as possible (try to see the edge of a razor blade for
example). Baffle spacing is a function of the angle of incoming light
and the depth of the baffles. One can estimate the spacing by
viewing the baffle from any point in the image plane..one should be able to
see only the baffle edges and back side of the baffle rings..but not
the cylindrical surfaces holding the baffles. More baffles than
that are superfluous and will actually increase the amount of
scatter because of the added number of edges.

Two and 3 stage baffles are used in space applications to
attenuate scattered light by factors of 10^4 to 10^6, in
this technique a baffle tube is shaded by a larger external baffle,
each stage attenyates by a factor of ~100.


Andy Saulietis
ISS Enterprises
10 Milky Way
Mayhill NM 88339


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