When to turn on dew heaters

[LaurenceT]

When setting up for an imaging session and giving the refractor time to cool down when should dew heaters be turned on, while the tube is cooling or when imaging session starts?

[The Lazy Astronomer]

I usually plonk my setup outside, with all lens caps on, around 30 - 60 mins before I want to use it; then plug everything in and power up when I go to polar align just before starting. Not had an issue with dew on the optics so far!

[Robny]

I normally let the environment sensor take control of that, but generally they're on about half power from first switching on the gradually increase power through the night

[bosun21]

I give my scopes about an hour to cool down before dark. I then start observing and at the first sign of dew on the tube or mount  I power up the dew heaters at about 50%. I will then increase/decrease the power depending on the severity of the dew formation.

[Moonshed]

I put my scope out about an hour before observing to allow it time to cool down. My Dew Heater is very basic and is either on or off that being the case it goes on as soon as it goes outside. Works for me.