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I cheat Pete by using dew straps to thermostatically heat my 300mm lens just above the ambient temperature before an imaging run starts. Focus once equilibrium is reached, and that way focus is maintained all night no matter what the ambient temperature does.
In Melboune 'summer' ambient on a clear night can be from 25C down to about 5C. In winter it can range from 16C to 1C. I leave the heater on 24/7 as that way my optic never gets condensation on it and it is always ready to roll at a moments notice.
This should work for your FSQ.
Bert
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