ATM Non-reflective paints and materials

["Anderson, Jay" <andeja@mail.va.gov>]

I recently opened an old refractor to find some baffles but many brass
and even polished (maybe chrome) parts inside.  In fact the inside of
the focuser tube was highly polished and chrome-like.  Since the scope
never had really good contrast I thought about painting all inner
surfaces a flat black.  When I did this the difference in contrast was
incredible--deep space was never so black!  I have run into some info
that may be of interest to all you ATMers who want to build better
scopes or improve your current scope:

The percent of reflected light from a material varies with the
wavelength and also the angle the light hits the material.  It seems to
me that the higher the wavelength the more light is reflected and more
light is reflected at more glancing angles.  Materials vary widely in
their
ability to absorb stray light within your telescope.  At 600nm
wavelengths black felt reflects 2%
of the light hitting it and black velvet (from a dress shop) reflects
0.25% (source: john.houldsworth@controls.eurotherm.com).  Though not as
good as velvet, flat black paints
can be used to reduce stray light.  I have heard a few paints mentioned
as being good.  Krylon Ultra-Flat Black and Nextel Flat black velvet
(now sold by the Ilinoise Institute of Technology's Research Institute
as MH2200, phone (312) 567-4432 o2 4326).

I found out that NASA uses a flat black paint called Aeroglaze Z306 to
absorb stray light within their optical systems, CCD and cameras and
used inside the Hubble telescope.  Hey, if it is good enough for NASA...
it is good enought for me.  I will try to find out more on this paint
and how to get it shortly.