[raymo]

The larger the scope, the smaller the detail that can be resolved. For instance
an 8" will show a lunar crater half the size that a 4" will. It is linear, so a 12"
will show one a third the size, and a 16" one a quarter the size.
Telescopes gather light according to the square of their diameter, so a 2"
gathers 4, a 4" gathers 16, a 6" gathers 36, and an 8" gathers 64, and so on.
that obviously means that an 8" [64] gathers light 4 times faster than a 4"[16], enabling four times as much data to be gathered in the same exposure time.
raymo