seeing at its basic level is two things
1. is your mirror at ambient?
2. is the atmosphere nice and still
1. 1 to 2 hours should see the mirror the same temp as your ambient, BUT, the ambient temp normally keeps dropping................but being in brisbane your overnight lows are not a long way from you day time highs.
Here in tassie, we might have 20 degrees during the day and 0 at night........20 degrees for a piece of glass to lose is difficult, hence I help it along by cooling
2.
http://weather.unisys.com/gfs/6panel...panel_aus.html and
http://www.wunderground.com/auto/vir...JetStream.html are two sites i always look at. what are the predictions for no movement in the air. Tuesday is looking goiod for tassie.....basically (as we already know) brisbane is still crap for seeing at the moment
get a feel for the twinkle of stars, if there is no twinkle, then it should be a good night
dp