Virtually all astronomers work in the daytime and sleep at night. The exception for some astronomers, is when they go 'observing' at optical or radio telescope observatories when the situation demands that they observe at night. Long ago, night time observing was the rule. Now a days, it seems like the exception, except if you are an optical astronomer, or your observing time was scheduled for night time because of the time of year and the location of the object.