Constellation, King
Cepheus
King Cepheus of Ethiopia, husband of Cassiopeia and father of Andromeda. One of its stars, Delta Cephei, gave its name to the Cepheids, stars that astronomers use to measure distances in space.
From New York, Cepheus never sets: it circles the pole and is highest at 9:19 PM on October 13, 2026, 62° above the horizon in the N.
In the 3D sky
The sky over New York turned towards Cepheus. Drag to look around.
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Evening visibility over the year
Height of the constellation’s centre above the horizon at 10 pm local time on the 15th of each month, from New York. Above about 30° it is well placed.
Name and history
Cepheus was the king of Ethiopia in the Greek myth of Perseus and Andromeda. His wife Cassiopeia angered the sea nymphs with her boasting, and Poseidon sent the sea monster Cetus to ravage the coast. The Oracle of Ammon told the king to chain his daughter Andromeda to a rock as a sacrifice. Perseus arrived in time to rescue her. The whole royal family is in the sky together, with Cepheus beside his queen and his feet almost at the north pole. Ptolemy described him wearing the tall headdress of a Persian king.
Its brightest star, Alderamin, takes its name from an Arabic word for the forearm, wrongly applied to this star by medieval European astronomers. In 1784 the young English amateur astronomer John Goodricke found that Delta Cephei brightens and fades on a regular cycle. Stars like it, the Cepheid variables, later became a key tool for measuring distances in space. Mu Cephei is known as the Garnet Star, after William Herschel described its deep garnet colour in 1783.
Sources: Ian Ridpath, Star Tales: Cepheus
Brightest stars
| Star | Designation | Magnitude | Distance |
|---|---|---|---|
| Alderamin | α Cep | 2.45 | 49 light-years |
| Errai | γ Cep | 3.21 | 46 light-years |
| Alfirk | β Cep | 3.23 | 685 light-years |
| ζ Cep | ζ Cep | 3.39 | 836 light-years |
| η Cep | η Cep | 3.41 | 47 light-years |
| ι Cep | ι Cep | 3.50 | 115 light-years |
| δ Cep | δ Cep | 4.07 | 865 light-years |
| ε Cep | ε Cep | 4.18 | 85 light-years |
| θ Cep | θ Cep | 4.21 | 137 light-years |
| Garnet Star | μ Cep | 4.23 | unknown |
Facts
| Area | about 588 square degrees (27 of 88) |
|---|---|
| IAU abbreviation | Cep |
| Sky | Northern sky |
| Origin | Listed in Ptolemy’s Almagest, about AD 150, from older Greek tradition |
| Stars brighter than magnitude 5 | 22 |
| Centre (J2000) | 21.9 h, 69° |
Deep-sky objects
Galaxies, clusters and nebulae brighter than magnitude 9, from the OpenNGC catalogue. Most need binoculars or a telescope and a dark sky.
| Object | Type | Magnitude |
|---|---|---|
| NGC7160 | Open cluster | 6.1 |
| NGC7023 · Iris Nebula | Nebula | 7.2 |
| NGC7380 | Cluster with nebula | 7.2 |
| NGC7234 | Open cluster | 7.7 |
| NGC6939 | Open cluster | 7.8 |
| NGC7510 | Open cluster | 7.9 |
| NGC0188 | Open cluster | 8.1 |
| NGC7261 | Open cluster | 8.4 |
Boundaries: International Astronomical Union, via Astronomy Engine. Areas are computed from the boundaries by sampling (within about one percent). Names and lines: Stellarium. Stars: HYG Database. Deep-sky objects: OpenNGC. Calculated with Astronomy Engine, an open-source library verified against the US Naval Observatory and NASA JPL. Data sources
How to use this page
Choose your place and a night at the top. The answer and the 3D view show where the constellation is, when it is highest and whether it rises at all from where you are. The chart shows its stars and lines, and the tables list its brightest stars and the deep-sky objects inside it.
Frequently asked questions
When is a constellation best seen?
When it is highest in a dark sky, which the page gives for the night you pick. Each constellation is best placed in a particular season, because the stars rise about four minutes earlier every night.
Why can I not see a constellation from my place?
Constellations far south of the celestial equator never rise from northern places, and those far north never rise from southern ones. The page says when this is the case.
What are the constellation boundaries?
The International Astronomical Union divides the sky into 88 areas with official boundaries. The stick figures are only a drawing aid, the boundaries say which constellation a point in the sky belongs to.
Related guides
- How to learn the constellationsStart with one bright pattern you cannot miss, use it as a signpost to its neighbours, and come back a month later: the sky will have turned, and you will know a little more of it.
- Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
- Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
- Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.