HOW SMALL A CRATER CAN WE SEE ON THE MOON?

-Lew Thomas 4-28-01

First we shall apply Dawes Limit, which strictly applies to the resolution of two equally bright points of light. This is

R" = 4.56/D    (1)

where

D = the diameter of the telescope objective in inches

R" = the resolving power in seconds of arc.

The mean distance of the Moon from Earth is 384,500 km. Therefore, the linear dimension of any object on its surface is

R = rq    (2)

where

r = the distance to the Moon = 384,500 km.

q = the angle of the Moon object subtended at the Earth observer in radians

R = the linear dimension of the Moon object in km.

Combining (1) and (2), we have

R = r 4.56p/(3600x180 D)

R = 8.5003/D    (3)

Using this relationship and assuming a perfect telescope, the following table is constructed