Right Ascension:

3 hours


-60 degrees

Area in Square Degrees:


Crosses Meridian:

9 PM, December 25

Visible Between Latitudes:

20 and -90 degrees

The constellation Horologium, the clock, is located in the southern hemisphere of the sky. It is visible from latitudes south of 23 degrees from October through December. It is a small constellation with a total area of only 249 square degrees. It ranks 58th in size among the 88 constellations in the night sky. It is bordered by the constellations Eridanus, Hydrus, Reticulum, Dorado and Caelum.

Horologium is not associated with any ancient mythology. It was named by the French astronomer Nicolas Louis de Lacaille in 1752 after his trip to the Cape of Good Hope to study the southern night sky. Lacaille named this constellation to honor Christian Huygens, the inventor of the pendulum clock in 1656-57. It was originally called Horologium Oscillitorium, “the pendulum clock” but was later shortened to Horologium, “the clock.”

The constellation Horologium showing common points of interest
The constellation Horologium showing common
points of interest below © Sea and Sky
Horologium constellation map
Horologium constellation map
© Torsten Bronger CC BY-SA 3.0
Name / Meaning
Object Type
V Mag
1 2 3 4 5 6 7
Alpha Horologii
R Horologii
Beta Horologii
Mu Horologii
Zeta Horologii
Eta Horologii
Iota Horologii
Orange Giant Star
Red Giant Star
Blue Giant Star
Yellow-White Subdwarf Star
Yellow-White Dwarf Star
White Dwarf Star
Yellow Dwarf Star

Horologium contains no bright stars. The brightest star in this constellation is Alpha Horologii with a visual magnitude of 3.85. It is an orange giant star located 314 light years from Earth. With a magnitude of 3.92, R Horologii is the second brightest star. It is a red giant star approximately 100 light years distant. The third brightest star is Beta Horologi with a magnitude of 4.98. It is a blue giant star about 310 light years from our solar system.

There are no Messier objects in this constellation but it does contain a number of deep sky objects, mostly star clusters and galaxies. It is also the home of the Horologium supercluster, which contains over 5,000 galaxy groups with over 300,000 individual galaxies. This giant cluster spans an area of space about 550 million light years across. Some of the most notable of these galaxies include a barred spiral galaxy called NGC 1433 and another barred spiral galaxy called NGC 1433, also known as Miltron's Galaxy. Unfortunately none of these can be see without a large telescope.

Hubble image of barred spiral galaxy NGC 1433 Miltron's Galaxy
Barred spiral galaxy NGC 1433, Miltron's Galaxy
© ESA/Hubble / CC BY 4.0
Hubble image of barred spiral galaxy NGC 1483 in Dorado
Barred spiral galaxy NGC 1483 in Dorado
© ESA/Hubble & NASA / CC BY 3.0