Wait for scope to cool... Then heat it up again with dew heater. Say what?

[kirkster501]

Does doing this promote currents of hot air in the tube?

Managed to get away without active dew control for two months but on my last observing run - a full eight nights ago because of s*** weather, my session was written off after one hour. So need to get soem active control.

Researching this...

Thanks, Steve

[Bizibilder]

Cooling from ambient (indoors?) at maybe 20° (or more) C above outside is quite a temperature differential and will take a scope quite a while to achieve. Dew bands, on the other hand, may only have to raise the temperature of your scopes lens/corrector plate (usually the worst case) by maybe 2-3 degrees to get them above the dew point and thus prevent dew formation. It will take far less time for equilibrium to be achieved.

[LukeSkywatcher]

Kind of ironic that we leave scopes out to cool and then warm the optics up again.

Its the done thing and works.

I dont use heated dew rings etc....................just a simple dew shield made from a camping mat.