It's summer here in the Southern Hemisphere and I'm learning how the modeling works in my Mach2. Two nights ago the temperature at night was high, around 20ºC and in almost all the frames of that night my stars were elongated, when the night before they were perfect. Then yesterday the temperature was 16ºC and the stars were perfectly round again.
My installation is semi-permanent, without any recent changes. I am using 4 minute unguided narrowband exposures and use a Pegasus Pocket Powerbox Advance to get the temperature.