In some embodiments, a catadioptric optical system (CDOS) including a centrally obscured reflective telescope is disclosed, which includes: a telescope compartment defining a telescope space therein, a primary reflector including a central opening and a secondary reflector. The reflectors are located in the telescope compartment. The CDOS also includes a mechanism for reducing temperature gradient in the telescope space. The mechanism includes an air duct including a first opening and a second opening; a hollow enclosure including side openings and one or more airflow generation devices. The mechanism is configured for forming an air passageway between the airflow generation device and the inner telescope space via the air duct and hollow enclosure located therebetween, for reducing internal air temperature gradient in the telescope space.