What it looks like
Horologium is a mid-sized southern constellation introduced by Lacaille in 1756, drawn as a pendulum clock — the instrument that made precision timekeeping possible and, in turn, precise navigation. Its stars are all faint, but it borders bright Achernar in Eridanus and contains the Horologium Supercluster, one of the largest structures in the nearby universe.
Brightest stars
Horologium has no bright stars; its brightest, Alpha Horologii, sits near magnitude 3.85.
| Star | Magnitude | Distance | Meaning |
|---|---|---|---|
| Alpha Horologii | +3.85 | 117 ly | — |
| Delta Horologii | +4.93 | 179 ly | — |
| Beta Horologii | +4.98 | 310 ly | — |
| Mu Horologii | +5.12 | 150 ly | — |
Mythology and history
Horologium has no ancient mythology. It was created by Lacaille in 1756 and named after the pendulum clock, the tool that made modern astronomy and navigation possible.
The astronomer's clock
Horologium was introduced by Lacaille in 1756 and named 'Horologium Oscillatorium' — the pendulum clock. Pendulum clocks, developed in the 17th century, allowed astronomers to measure the positions of stars with unprecedented precision and to determine longitude at sea, transforming both astronomy and navigation. Like its neighbour Caelum, Horologium belongs to Lacaille's group of scientific constellations, and its quiet stars belie its role in the history of measurement itself.
How to find it
Look just west of brilliant Achernar in Eridanus on late autumn and winter evenings from the southern hemisphere.
- Find Achernar, then look west for Horologium's faint stars.
- No star brighter than magnitude 3.9 — use a chart.
- Best from the southern hemisphere and low northern latitudes.
Key facts
- Abbreviation
- Hor
- Genitive
- Horologii
- Meaning
- The Pendulum Clock
- Brightest star
- Alpha Horologii
- Main stars
- 4
- Area rank
- 58th
- Best visible
- December
- Declination
- -50°
- Meteor showers
- —
- Neighbours
- Eridanus, Caelum, Dorado, Reticulum, Hydrus
Deep-sky objects
Horologium contains the Horologium Supercluster, one of the largest and most massive structures in the nearby universe, spanning about 550 million light-years. The constellation also contains the globular cluster NGC 1261 and the faint spiral galaxy NGC 1512.
Frequently asked questions
What does the constellation Horologium look like?
Horologium is a faint southern constellation named for the pendulum clock, sitting west of brilliant Achernar and containing no star brighter than magnitude 3.9.
What is the brightest star in Horologium?
The brightest star in Horologium is Alpha Horologii, shining at around magnitude 3.85.
When is Horologium best visible?
Horologium is best seen from southern hemisphere during December.
What is the story behind Horologium?
Horologium has no ancient mythology. It was created by Lacaille in 1756 and named after the pendulum clock, the tool that made modern astronomy and navigation possible.
Which constellations are near Horologium?
Horologium borders Eridanus, Caelum, Dorado, Reticulum and Hydrus.
Eridanus
Dorado