"LOONEY 11 RULE:
The “looney 11 rule” states that for astronomical photos of the Moon’s surface, set aperture to f/11 and shutter speed to the (reciprocal of the) ISO film speed (or ISO setting).”
With ISO 100, one sets the aperture to f/11 and the shutter speed to 1/100 or 1/125 second.
With ISO 200, aperture at f/11, set shutter speed to 1/200 or 1/250.
With ISO 400, aperture at f/11, set shutter speed to 1/400 or 1/500."