Outside temp colder than cooled camera!

[Icesheet]

I was imaging last night and set the cooler on my camera to -10deg as usual. However, towards the end of my session I noticed the camera thermometer was showing -13deg. Sure enough it was colder than -10 last night. 
 

I was planning on shooting darks today but should I shoot them at -10 or at -13? Anyone had this issue before?

[vlaiv]

It might be that some subs were taken at -10C, some at -11 and some at -13C

I would personally inspect fits headers to see what actual temperatures are there and then shoot set of darks for each of them, but as a first step - I would use regular -10C master dark to see how bad result will be (it might turn out quite fine).

If your camera is CCD - you don't have to worry about that - you take set of bias subs and use dark optimization/scaling. That should provide you with good dark calibration. You can just use your regular -10C darks that you would otherwise use.

[Icesheet]

Thanks. I’ll look to see how much variation there is on temp on the FITS headers then. I need to shoot some new master darks so I might as well shoot them for -10 and see how it goes as you say. I’ll need to remember that next time I’m out.