Frequently Ask Questions (FAQ)
Air-spaced flocked tube liner
(last updated June 14, 2006)
1) I'm confused. I've heard that the tube wall should not be an insulator?
I'm confused. I've heard that the tube wall should not be an insulator?
It is a little confusing, since catadioptric telescopes (e.g., SCT, Maksutov-Cassegrain, Maksutov-Newtonian) will benefit from a tube wall that has a high thermal conductivity. Their closed-tube design traps the heat, and conduction of heat through the tube wall is the main path for heat to escape.
The open-tube (or even truss design) Newtonian does not have this problem, and the majority of the heat escapes out the open end of the tube. In most cases, the tube itself plays an insignificant thermodynamic role. However, an exception is a metal tube, which suffers from the "cold wall" problem. This is easily solved by insulating the inside wall.