idea for dew heater

[Arthur Alchin]

I have made a dew heater and DC voltage controller for my LXD75 8"SN which, when tried at lostock in a week or two will work well but another idea has come to mind and i am enquiring as to whether or not have thought this out

Is there any credibility in making a "tube heater" ie. a short length of tube (diameter about 75 -100mm depending on the size of the opening on rear of scope) with a heating element (either resistors or nichrome wire) of about 10-15 watts (variable of course) and directing this warm air into the scope through the opening behind the primary mirror (newtonian type scope here) using a 12v computer case fan?? power use by the fan is minimal, output is gentle, noise in minimal.

Any thoughts on the subject

[Starkler]

Whats desirable is to have the optics as close to ambient temperature as possible without dew forming. You certainly dont want to be pumping heat inside newtonian or sct tubes!

[montewilson]

This makes sense except for the turbidity it would introduce into the air in the scope. Basically you would have terrible seeing all the time even when the skies are perfect.

It would be a bit like saying the patient died but the operation was a success.

But don't be put off, lateral thinking is what Am-Ast is all about.

Low heat applied to the directly to metal of the scope is the best way.