Oh I can set it to -40º below ambient. But usually I set it to a target of -15ºC (with an ambient temperature of around 10ºC, this winter I might go a bit lower). Not stressing the PEC is gentler on the battery too. You have to be slightly careful when doing cooldown and warmup to avoid condensation and thermal shock (or at least, I think I should be), but I've never had any problems with it.

Also great shot! I feel your pain with the wind, dew and bugs... but it's still an awesome hobby.