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Originally Posted by Dennis
Hi
I found this link http://tinyurl.com/bzbv7 in a discussion in the C9.25 Yahoo Groups. It points to a flocking thread on sci.astro.amateur in which luminaries such as Roland Christen (Astro-Physics) made comments. Well worth a read (if the link still works!).
Cheers
Dennis
PS - to whet your appetite, here is an excerpt from that thread which spawned some quite interesting discussions.
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"Flocking doesn't change the sharpness of the optics, does not eliminate
any optical aberrations, does not smooth out rough surface finish, does not
reduce the central obstruction, etc. These are the primary things that affect
planetary contrast. Flocking does affect the ability to see faint deep sky
objects in light polluted skies, but again does not help any in really dark
skies. Planets are so bright with respect to the background sky, that it makes
virtually no difference if baffles are there or not. The light from the planet
is blocked from coming directly into the eyepiece by the secondary mirror, and any light that does come in on the side from the background sky does not have enough brightness to register with respect to the planet itself."
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All those points are correct, but they left out the most important one! (well for high res imaging, is there anything else?
) Flocking isolates the air from your tube so that "supercooling" of the metal tube under the night sky won't cause waterfalls of cold air to start running down inside your scope and across the mirror.
It also (slightly) reduces the ability of the air inside the tube to lose heat as it's no longer in direct contact with the metal, but for people with open ended tubes this isn't a problem anyway.
I'm very happy with the results on my tube, I bought adhesive black felt from one of the craft stores, but in hindsight the mitre10/bunnings idea sounds like the better one. Felt does shed a little when you first put it in the tube, but that stops after w hile when all the loose fibres have come out.
Bird