M 48 is an open cluster in the constellation Hydra, very
near its border with Monoceros. It is made up mostly of
young, hot blue stars, about 300 million years old. It is
23 light years in diameter, and 1500 light years from earth.
It was noted by Messier in 1771, but he made a mistake in
recording its location, and so it was "lost" from the Messier
list until 1934. In the meantime, it had been found and noted
by Caroline Herschel in 1783, and came to be catalogued as
NGC 2548. Under dark skies, it is visible to the unaided eye.

Image data:
Camera: Canon 350 XT (modified)
Telescope: William Optics 66mm ZS, Baader MPCC
Exposure: ISO 800, 5 minutes x 22