Object note
Andromeda Galaxy
The most distant thing most people will ever see with their own eyes, and almost always a disappointment the first time.
- Designation
- M31
- Distance
- About 2.5 million light years
- Apparent size
- Roughly 3 degrees across
- Best season
- Autumn, northern hemisphere
Why it disappoints
Photographs show a bright, structured spiral. What the eye sees is a faint grey smudge, and the reason is straightforward: the eye is a poor detector for low light compared with a camera, and the galaxy's light is spread over an area several times larger than the full moon.
The core is what is visible, not the spiral arms. Expecting the photograph is the single most common reason people conclude their telescope is faulty.
Finding it
The usual route is from the Great Square of Pegasus, hopping along two stars of the Andromeda constellation. The galaxy sits close to the star Mirach, and is easy to locate with binoculars once the hop is learned.
It is genuinely visible to the unaided eye from a dark site, as a small fuzzy patch. From a suburban garden it usually is not, but binoculars recover it easily.
Two companions
M32 and M110 sit near the main galaxy and are both within reach of a small telescope. M32 in particular is compact and bright, and is often mistaken for the core of M31 by people who have not seen the pair before.
What actually helps
- A dark site. Far more important than aperture for this object.
- Low magnification. The galaxy is large and faint; more power makes it worse.
- Averted vision. Looking slightly to one side of the object genuinely reveals more.
- Patience. Dark adaptation takes twenty minutes or more, and is easily undone by a phone screen.