i have a few to put up
... just looking through them now.
It was difficult to tell the precise temp, because my strip gauges were underneath and i forgot to add some outside... but nick gave me one with 5 degree increments and it was around 25, with no sun... and the scope didn't shift. So current thinking is that it's the heat that it gets up to under sunlight which makes it go up in temperature much higher and shift.
Could be cryrogenic cooling systems are the way forward
However, the first day started at 5pm and finished at 9.30, and although there was light, with the low cloud it was getting dark on some targets... i heard a few struggled with that, but the march was superb in the dark, even on 60x it had superb definition... it was only when i heard that people had a problem that i realised there was one!