[Robh (Rob)]

Mark. This is what I've noticed.
Let's say you were looking at the planet Jupiter through your reflector.
As your mirror is cooling down, the convection currents will result in a flaring effect around the disk. The planet looks fuzzy and "hot".
Once the mirror is acclimatised, air turbulence will have the effect of pulsing the planet in and out of focus, clear one second then fuzzy the next. I think moving wave fronts or eddies caused by the jet streams 10kms high are the probable cause. Anyone else with ideas?

Regards, Rob