[ATM] Shroud v.s no shroud

[Mel Bartels]

> Hi Mel
> I think most folks would benefit from the hour or so it takes to try it.

Absolutely do the test!  I like to conduct the test sans eyepiece and eye
cupped tightly to the focuser.  A bright light is shined around the scope by
your friendly lab assistant, the light being turned on and off at random.
You should not be able to detect when it is on or off.  

If you can see light, then inspect where the light is being reflected from,
hide or dull that surface, and try again.  All light entering the focal
plane is reflected from a real surface (mirror on purpose, other structures
by accident) or comes directly from the light source.  Important to get away
from the fuzzy thinking (I say this because I have this tendency) to feel
that someone light fuzzes around and can waft in and out, like a breeze
bends around corners.

Baffles are to solve the problem of good air in, bad air out.  I see three
patterns of baffles:

1. light path baffle
2. scope structure baffle
3. external baffle

example of 1: light baffles placed sequentially down a refactor's tube
example of 2: shroud; baffle opposite the diagonal
example of 3: an observatory structure or temporary tarp surrounding a scope

On #3, I think there's lot of room for innovation on lightweight snap open
baffle, say a meter by 2 meters that could be moved around the scope.  This
could also serve to control dew, prevent those car headlights from killing
you (and you subsequently killing the driver), et al.

Mel Bartels