We cruised Alaska in 2008 and had a very good time. Actually, we took two cruises, back to back, visiting essentially the same ports and areas. This proved to be convenient because the weather was quite variable and a couple of the major points of interest would have been lost if we had not had two visits. Out of 14 days, I got one good set of sunset images.
Be aware that you will, most often, be at sea during sunset and sunrise, Check
http://photoephemeris.com/ for a program that will show you sunrise, sunset, moonrise, moonset times and azimuth. Sunset times will be around 10PM, sunrise around 2AM.