In photographing the moon, when low on the horizon, how long a shutter speed can be used before the motion of the moon becomes evident. Also I am uncertain abou t exposure; I believe one should calculate the value as if exposing for the sun but I am a bit uncertain. Has anyone had any experience using graduated neutral density filters for moonscapes? I will be shooting over the ocean just at, and a bit after, moonrise.

Thanks for the help.

DAB