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Hi Mark,
In general terms Perth's seeing is usually pretty rubbish in summer, but it's winter that we do get the good occasional night. My suspicion, given the amazingly cold mornings we've been having is that you took your scope from a warm house to 3 degrees outside, and didn't give it the hour it needed to come to equilibirum (by which time it probably would have started to dew up).
One way of telling if the jetstream is about (our main source of poor seeing) is to de-focus and have a look at the turbulence in the out of focus image.
I wasn't up at 3, but earlier in the evening the seeing was fair.
cheers,
Andrew.
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