1 / film speed at f8 1/2 - f11. If the camera will do multiple exposure on the same frame, consider putting a giant moon with the cat, and them put some other recognizeable landmark in the same frame. Check out the pink moon shot at my poor little web site. Done many many years ago and alas no pretty lady to distract and I still managed to have the moon smash into the mountains. Still it works and I get requests for it all the time.