Thanks for the advices guys. So what after you open the observatory for observing? Do you still keep the AC system running? In my place if we don’t do that the temperature and humidity is too high. But if we do it my concern is it will have impact to telescope performance as there will be some turbulence within the observatory. I asked a few friends in big observatories and it seems they all shut the AC system down during observing.
Most would, but not all. The AAT air conditioning system was designed to operate with the dome open without any deleterious effects, but this is probably unusual. If you can use an air conditioner to maintain a pool of cooler air below the telescope without impacting on the incoming beam, then yes it is worthwhile as it will reduce risk of warm plumes rising into the beam. But it has to be designed and engineered to achieve that, otherwise you risk mixing warm and cooled air within the dome and in the beam, which will destroy the seeing.
Edited by Oberon, 15 September 2021 - 09:50 AM.