What is the DOG WATCH? It is the term for a period of work duty on shipboard, between 1600 and 2000 hours, or in civilian terms, 4pm - 8pm. It is said to derive from Sirius, the dog star, the first star to come in view in the first dog watch. Actually there are two work periods within this watch: one at 1600-1800 hours, and one at 1800 to 2000, but the first is actually when there is still day light, before the stars come out.
An alternative explanation suggests that in these 1/2 watches, the sailors are "dodging the watch", and it was later, then, shortened to dog watch. Perhaps..............
Whatever the explanation, my favorite pun regarding this watch comes from the Master and Commander books, calling this short watch "cur-tailed!"
But back to some more "serious" maritime information: Sirius, the Dog Star, is the brightest star in the nightime sky, and therefore plays an important role in navigation, which until much later was the principle way of keeping on course. Sirius is in the constellation Canis Major, and by the way, the word "sirius" comes from the Greek meaning "scorching", for the star's incredible brightness.
Interestingly enough, for those who follow the Harry Potter series, one of the principle characters, Harry's godfather, in fact, is Sirius Black (shown below), who is an unusal type of wizard, an "Animagus", or one that can shape-shift into an animal! And, what, pray tell, do you think is Sirius' animal of choice?!
We now rely on computer technology to guide us, as far as we can image, even out into space, but some of the tools shown below, were the sailor's only way to travel from "here to there" in the age of sail, including sextant, compass, and the good old telescope!