Theoretically you should not be able to create sharp photos of the stars using long exposures from the deck of a moving ship. But I decided I had nothing to lose by trying. At the worst I would end up with throwaway slides.
So I set up a tripod, camera, and 15mm lens and went to work. I was using slide film so I could not check my results as I went along, so I experimented with the exposures.
The 15mm semi-fisheye lens has a lot of depth of field so I manually set the focus at infinity and left it there. This lens also creates some field curvature which is why the horizon and railing of the ship are curved.
I made exposure notes for the group of photos, but not for each individual frame. I set the aperture at f/2.8 and used shutter speeds of 8 sec, 15 sec, 30 sec, 1 minute, and 2 minutes. It is my best guess that this particular photo is a 1 minute exposure.
This photo worked as well as it did because the water was so smooth and the ship held such a steady course that the stars “burned in” on the film for most of this long exposure. And then the ship turned to the right during the last part of the exposure, so each star created a little streak.
So if you are on the deck of a ship and want to try some night sky photography, you have nothing to lose by trying. I suggest a wide angle lens and a wide aperture. Thanks to digital photography you can use a higher ISO and shorter shutter speeds. Start with an ISO of 800 or 1600. Experiment with shutter speeds between 4 and 30 seconds. If the stars move too much, raise the ISO and shorten the shutter speed.
For those of you who are curious about the night sky and what you are looking at, I labeled the North Star (Polaris) and several constellations.
Photo data: Canon Elan IIe, 15mm lens, f/4, about 1 minute. Kodak Elite Chrome 200 slide film at 640 (push 2).