Algol: how to find it and when to see it
Algol ranks 59th of the 74 bright stars on our list, at magnitude 2.09, in the constellation Perseus.
You can see it from anywhere north of 49° S, and it's highest in the evening sky in December.
Algol at a glance
Where Algol is in the sky
Algol sits 41.0° north of the celestial equator, the line in the sky directly above Earth's equator, so it's in the northern half of the sky. Its right ascension is 3 h 8 min.
Right ascension works like longitude on the sky. It's counted in hours, and about one hour of it turns past you each hour of the night.
When and where to see Algol
From the northern hemisphere
From 40° N, the latitude of New York, Madrid and Beijing, Algol rises in the north-east, climbs to 89° above the horizon in the north and sets in the north-west.
It's in the evening sky from September to April, and it's highest in the evening around December 23, in winter.
From the southern hemisphere
From 34° S, the latitude of Sydney, Cape Town and Buenos Aires, Algol rises in the north-east, climbs to 15° above the horizon in the north and sets in the north-west.
It's in the evening sky from December to January, and it's highest in the evening around December 23, in summer.
How high Algol climbs from each latitude
The evening is about 9 pm local time, or 10 pm in summer time, and later when the sky is still too bright. A star counts as in the evening sky when it's at least 10° above the horizon.
| Latitude | Visibility | Highest point | Evening sky |
|---|---|---|---|
| 60° N | Never sets | 71° in the south | All year |
| 50° N | Never sets | 81° in the south | Aug to Apr |
| 40° N | Rises and sets | 89° in the north | Sep to Apr |
| 30° N | Rises and sets | 79° in the north | Sep to Mar |
| 20° N | Rises and sets | 69° in the north | Oct to Mar |
| Equator | Rises and sets | 49° in the north | Oct to Feb |
| 20° S | Rises and sets | 29° in the north | Nov to Feb |
| 34° S | Rises and sets | 15° in the north | Dec to Jan |
| 45° S | Rises and sets | 4° in the north | None |
What the name Algol means
Algol comes from the Arabic raʾs al-ghūl, the head of the demon. It marks the head of Medusa that Perseus holds.
Keep the sky of a night that matters
Our star maps show the stars above any place, at the minute you choose, with the constellation lines drawn in. If Algol was above the horizon that night, it's on your map, and we print it on museum-grade paper.
Questions about Algol
Algol is in Perseus. It sits 41.0° north of the celestial equator, at a right ascension of 3 h 8 min.
Algol is highest in the evening sky around December 23. That's winter in the northern hemisphere and summer in the southern hemisphere.
Yes, from anywhere north of 49° S. From 34° S, it climbs to 15° above the horizon in the north.
Algol has a magnitude of 2.09, which ranks it 59th of the 74 bright stars on our list. Sirius looks about 26 times brighter.
Algol comes from the Arabic raʾs al-ghūl, the head of the demon. It marks the head of Medusa that Perseus holds.