Update: my dew heater quit at 2am in the middle of the Andromeda shot
I drove out to a dark site near Pawnee National Grassland on Saturday to finally get a clean 3 hour run on M31 with my little 72mm scope, and around 2am the dew heater just died on me. Within 20 minutes the corrector plate was fogged solid and every sub after that came out soft and useless, so I lost maybe 90 minutes of data and packed up freezing and annoyed. Has anyone found a dew heater that survives a full cold night, or should I just start bringing a backup controller and a spare USB battery?