Finding your way around the sky

Height and direction

Altitude is how high to look; azimuth is which way to face.

Astronomers measure the sky in degrees: 360 in a full circle (opens in a new tab), so a half-turn is 180. Altitude runs from 0° at the horizon to 90° straight overhead; azimuth is the compass direction, measured clockwise from true north: 0° north, 90° east, 180° south, 270° west.

Use true north, not magnetic north. Polaris marks true north (opens in a new tab), the direction of the geographic pole; a compass points to magnetic north, which is a different place.

Sources for this section NASA Science, Skywatching FAQ (2024) (opens in a new tab) · ; Preston Dyches, What is the North Star and How Do You Find It?, NASA Science (2021, updated 2024) (opens in a new tab)

Measure with your hand

At arm's length, a little finger is about 1°, three fingers about 5°, a fist about 10°.

NASA's skywatching FAQ (opens in a new tab) gives the rule: held at arm's length, the width of your little finger covers about a degree, three middle fingers about 5 degrees and a fist about 10.

So “20° up” is two fists above the horizon, and “about 36° (opens in a new tab) south of Sirius”, where Canopus is, is three and a half fists. Hands and arms vary, but the rule holds well enough to find things.

Sources for this section NASA Science, Skywatching FAQ (2024) (opens in a new tab) · ; Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab)

Give your eyes time

Let your eyes adapt for about twenty minutes, and use a red light.

The Night Sky Network (opens in a new tab) advises letting your eyes adjust to the dark for twenty minutes before judging what you can see, and using a red light to read charts without losing your night vision.

Bright lights undo it quickly: avoid them (opens in a new tab), the Network says, if you want to see faint things like the Milky Way.

Sources for this section Kat Troche (Astronomical Society of the Pacific), Check Your Sky Quality with Orion!, NASA Night Sky Network (2023) (opens in a new tab) · ; Kat Troche (Astronomical Society of the Pacific), The Great Rift, NASA Night Sky Network (2025) (opens in a new tab)

Star-hopping

Start from a pattern you know and follow its lines to the next.

In the north, start with the Big Dipper. Its two end stars point to Polaris (opens in a new tab); the curve of its handle arcs to Arcturus (opens in a new tab).

In the winter evening sky, start with Orion's belt. Follow it one way (opens in a new tab) to Sirius; look the other way, west of Orion, for the Hyades and the Pleiades (opens in a new tab).

In the south, the Southern Cross (opens in a new tab) helps find due south, and Alpha and Beta Centauri (opens in a new tab) point to the Cross.

How to see it Begin with one landmark and one hop a night: the Big Dipper, Orion or the Southern Cross, depending on where you are and the time of year (opens in a new tab). The sky finder tells you which are up.

Sources for this section Preston Dyches, What is the North Star and How Do You Find It?, NASA Science (2021, updated 2024) (opens in a new tab) · ; NASA Science, What's Up: September 2021 (opens in a new tab) · ; NASA Science, What's Up: December 2024 (opens in a new tab) · ; Kat Troche (Astronomical Society of the Pacific), Spot the Young Stars of the Hyades and Pleiades, NASA Night Sky Network (2023) (opens in a new tab) · ; Ian Ridpath, Star Tales: Centaurus (opens in a new tab) · ; NASA Space Place, What Are Constellations? (updated 2022) (opens in a new tab)