Re: [ATM] How dark is dark

[Andy Saulietis <iss@pvtnetworks.net>]

Re measuring telescope baffling..

The ONLY thing that counts is the amount of non-imaging stray light 
reaching the focal plane. If you have
a CCD camera plug fit into the scope, point it at a dark sky and take 
exposures with the various types of paint
and baffles. The average of the pixels tells the tale.

When I was designing baffles for the Shuttle Star trackers and other 
optical sensors, we found that
using specular coatings made it *difficult* to predict the actual 
performance and iterate the design to minimize
stray light. We chose to use flat black which made modeling the 
baffle system much simpler, especially
in the days of DOS and DIY programming.

I still use #1604 Krylon  Ultra Flat Black..cheap and it works. A 
dark sky helps also..<g>

Andy Saulietis


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