Cooling fan essential.

Hello,
You think that a cooling fan is essential in a Maksutov-Cassegrain of 5.5" or 6" ?

Thanks,
Paulo

Largely depends on your location, a 6” MC is small enough to function without cooling fan if your observing location experiences temperature drops in the range of 20 to 25º F during day and night. In high and dry locations where temp variations can reach 40º F you will need some form of active cooling to keep up with the ambient during rapid temperature drops that begins right after the sunset.

Vahe

Depends on where you live, and, to some extent, the scope. Down here on the Sunny (and hot and humid) Gulf Coast, my ETX125 is fine without one.