Dew on primary and secondary

[D Wright]

I had a problem last night with my 130PDS that I have never had before. Both the primary and secondary mirrors dewed up. I use a foam dew shield but this didn't seem to help much. Does anyone know how to get round this problem. I know you can get secondary dew heaters but what about the primary. Is this a drawback of a short tube reflector?

[Luna-tic]

Dew is humidity and temperature directed. A shield may delay the onset (same as having the tube horizontal rather than vertical), but won't prevent it.  Was the air cooler last night than it has been, or has it been more humid? Weather changes sometimes mean dew when you had none before.

[tooth_dr]

Noticed a very heavy dew when I was out a couple of night ago, the dew heater struggled to keep it off the lens. Literally everything was soaking.  It must be bad to get dew on a primary mirror. 

[D Wright]

It was very cold (-2') but I didn't notice much dew on other things.