From: "Thomas A. Moulton" 
To: 
Cc: 
Reply-To: "Thomas A. Moulton" 


> What is the preliminary mode of heat transfer in telescopes?  Is there
> a dominant mode or does it change from design to design?.  Tom Krajci
> mentioned radiation in the wire spider thread.  Tube currents suggest
> convection.  Blowing air with a fan through the cell onto the back of
> the primary is convection and conduction.

> I am probably naive, I just don't see radiation being large in a spider
> or secondary setup, I would ( and have ) assumed that for spiders all
> three modes are operating with convection/conduction being dominant.
> As optimizing heat transfer requires identification of the modes, I am
> interested in this before I start constructing my bino scope ( actually
> I have started building already :) ).

Heat is *very* important!

Think of your spider and diagnoal as a match (or Bon Fire) in front of the tube!

I think the problems occur from radiation and some relief can be gotten by
conducting the heat to outside the tube so it is not in the line of
sight...

But The good news is that once the heat is 'gone' it is not an issue... so
the idea with fans is turn them on let things stablize and turn them off or
slow them way down...

Fans also vibrate which is also bad..

Isn't it fun?

tom

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