View Single Post
  #18  
Old 27-04-2009, 08:23 AM
Omaroo's Avatar
Omaroo (Chris Malikoff)
Let there be night...

Omaroo is offline
 
Join Date: Aug 2006
Location: Hobart, TAS
Posts: 7,639
Alright Monte - gloves off! LOL!!

The only reason that I can see to heat the glass itself would be to raise the temperature of the air right at the glass/air interface - such that it's dewpoint is raised. Dew condenses out of air, not glass. Therefore - heating the tube with the intent of heating the glass, in turn, services this requirement because you are radiating heat from the glass into the adjacent air - as does heating the air at the bottom of the dew shield anyway like I do. Same thing - only one is possibly slightly more efficient that the other in terms of the volume of air that we are heating. A dew shield provides an air trap, of sorts, in order to keep some of the previously warmer air (from the earlier part of evening) close to the glass so that it doesn't approach the dewpoint as quickly as air further up near the open end of the dewshield, which is at ambient temp and probably falling. The differential need only be a couple of degrees. I wouldn't mind engaging in a conversation with a qualified thermodynamicist to see what the crux of the matter really is. I'll get back...

At the end of the day - I guess I'd rather heat air than potentially alter/deform the refractive qualities of a finely ground and collimated fluorite objective by heating it directly. Hmm... the debate rages on... LOL!

Last edited by Omaroo; 27-04-2009 at 08:49 AM.
Reply With Quote