How to See the Andromeda Galaxy With Your Own Eyes

Almost every star you can see at night belongs to our own galaxy, the Milky Way. The Andromeda Galaxy is the big exception. It is a whole separate galaxy of stars, and on a dark autumn night you can see it without any equipment. Royal Museums Greenwich calls it "probably the most distant object you'll manage to see with the unaided eye."

The catch is that it does not look like the photos. Knowing what to expect, and when and where to look, is most of the battle.

1. The numbers behind the smudge

NASA's Hubble team describes Andromeda, also called Messier 31 or M31, as "the nearest major galaxy to our own." A few figures from NASA's pages:

• Distance: about 2.5 million light-years. The light reaching your eyes left the galaxy about 2.5 million years ago. NASA's Night Sky Network puts it vividly: it left "when our earliest ancestors figured out stone tools."
• Size on the sky: "six times the apparent diameter of the full Moon" from end to end.
• Brightness: NASA's Hubble catalog lists an apparent magnitude of 3.1, and the Night Sky Network describes it as "a 3.4 magnitude patch of haze." Either way, it is bright enough for the unaided eye from a dark site.
• Stars: the Night Sky Network estimates a trillion of them.

Despite that enormous size, you will not see a big spiral with your eyes. NASA's Night Sky Network describes the bright core as the part that stands out, with only a bit of the disk showing even in binoculars.

2. When to look

NASA's Hubble page says M31 "is best observed in November." The Night Sky Network adds that its constellation, Andromeda, "becomes prominent as autumn arrives in the Northern Hemisphere." Autumn and early winter evenings in the Northern Hemisphere are the prime season.

3. Where to look

NASA's Night Sky Network describes Andromeda as a fuzzy, star-like object "located near the border between the constellations of Andromeda and Cassiopeia," and recommends using "the Great Square of Pegasus or the Cassiopeia constellation as guides to find it."

Cassiopeia is the easier starting point for beginners. Royal Museums Greenwich describes it as a zig-zag that looks like a W at some times of year and an M at others. In the Northern Hemisphere it is circumpolar, so it is above the horizon on every clear night. The galaxy sits in the region between Cassiopeia and the large, four-star Great Square of Pegasus.

Because the galaxy is faint and the area has no single bright marker, a star chart or stargazing app is a big help for your first attempt. Royal Museums Greenwich suggests a planisphere or app, with a red filter on the app so the screen does not spoil your night vision.

4. What you will actually see

With the unaided eye, expect a small, faint, fuzzy patch, not a sharp point like a star. The Night Sky Network describes "surprising amounts of detail" from truly dark sites and "hints of it" even from light-polluted areas.

Two techniques help:

Use averted vision. Royal Museums Greenwich recommends looking "a bit to the side" of a faint object while concentrating on it. Their explanation: the eye's cone cells, which handle color and fine detail, cluster in the center of the eye and work best in bright light, while rod cells, which handle low light, are concentrated toward the edges. Looking slightly off to the side puts the faint glow on your rods.

Give it time. The Night Sky Network notes that "persistent stargazers can still spot M31's core from areas of moderate light pollution as long as skies are otherwise clear." NASA's Hubble page agrees that it can be seen "even in areas with moderate light pollution."

5. With binoculars or a small telescope

The Night Sky Network describes the step up:

• Binoculars: "M31's bright core stands out, along with a bit of its wispy, saucer-shaped disc."
• Telescopes: more detail, but they "often can't view the entire galaxy at once" because it is so large. Under good skies you may pick out two of its small companion galaxies, M32 and M110.

Thin clouds, smoke, or haze "will severely hamper observing fainter detail," so a clear, dry night beats a hazy one even at the same site.

6. A little history while you look

Andromeda has been noticed for over a thousand years. NASA notes that the Persian astronomer Abd al-rahman al-Sufi's The Book of Fixed Stars, from the year 964, contains the first known report of it. For centuries it was called the "Andromeda Nebula." According to the Night Sky Network, astronomers argued over its nature in the "Great Debate" of 1920, and a few years later Edwin Hubble, building on Henrietta Leavitt's work with Cepheid variable stars, showed it lies far outside the Milky Way.

7. Your Andromeda checklist

1. Pick a clear autumn or early winter evening.
2. Get away from nearby lights; a moderately dark site can be enough.
3. Find Cassiopeia's W or M shape, then scan the area between it and the Great Square of Pegasus with a chart or app.
4. Look for a faint, fuzzy smudge rather than a star, using averted vision.
5. Bring binoculars to see the bright core and a hint of the disk.

8. Key takeaways

• The Andromeda Galaxy is about 2.5 million light-years away and is likely the most distant object you can see without equipment.
• NASA says it is best observed in November, so autumn and early winter evenings are ideal in the Northern Hemisphere.
• Look near the border of Andromeda and Cassiopeia, using Cassiopeia or the Great Square of Pegasus as guides.
• To the eye it is a faint fuzzy glow, mostly its core; averted vision makes it easier to see.
• Binoculars reveal the bright core and part of the disk, and it can be found even under moderate light pollution.