Originally Posted by jackdale
And it beats having to climb the mast to change the anchor light.
Not only that, but it makes the anchor light much more likely to be seen at close range. A little light perched 40, 60, 80' up, on the top of a mast, is often easy to miss from other boats moving around in an anchorage (e.g., other boats looking for a place to anchor, and tenders). Additionally, a lantern will often light up the deck a bit, making the boat even more visible at very close range (as well as making it unnecessary to carry a flashlight when moving around on deck in the middle of a moonless night).