What is the largest and smallest constellation?
Stretching from the northern hemisphere, where it borders Cancer, Hydra winds down to the southern sky, where it meets Centaurus. It includes many bright stars, but its total area covers over 1,300 square degrees.
It is best seen from the southern hemisphere, but is also visible in the north from January through May.
The smallest constellation is Crux, the Southern Cross. A small group of four bright stars that forms a Latin cross in the southern sky, Crux is visible from latitudes south of 25 degrees north and completely invisible in latitudes above 35 degrees north (in the United States, roughly north of Texas).
Originally it was part of the constellation Centaur, but became its own constellation during the 16th century when it was used as a valuable navigation tool by explorers. Its area is calculated at about 68 square degrees.
Here are some links to more sources of constellation information:
—The Fact Monster