<p>The answer is right there in your screenshots. The 'dimensione' or angular diameter on the sky is 3 degrees for M31, whereas the moon has an angular diameter of only 0.5 degrees. In other words, M31 is about 6 times as wide as the moon.</p>

<p>As wikipedia correctly states, you need a large telescope to see the full extend of M31. With the naked eye of even a small telescope you simply cannot see the spiral arms. </p>

<p>I think this image shows it very neatly:
<a href="http://apod.nasa.gov/apod/ap061228.html">http://apod.nasa.gov/apod/ap061228.html</a></p>

CC BY-SA 3.0
2013-11-27T12:17:27.293Z
2013-11-27T12:17:27.293Z
Michael B.
<p>I am trying to understand something I read on wikipedia about M31.</p>

<p>Wikipedia says that M31 appears more than six times as wide as the full Moon.</p>

<p>But I remember that when I watched it naked eye it seamed a lot smaller, even considering that I was able to see only the central region. For this reason I also used the software Stellarium to check it and setting the same magnification for the two objects (see pictures), the wikipedia information still seems wrong ... or most likely I am wrong!</p>

<p>Where is that I fail? </p>

<p>"At an apparent magnitude of 3.4, the Andromeda Galaxy is one of the brightest Messier objects,[15] making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution. Although <strong>it appears more than six times as wide as the full Moon</strong> when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using binoculars or a small telescope"</p>

<p><img src="https://4coloring.files.wordpress.com/2013/11/m31.jpg" alt="M31"></p>

<p><img src="https://4coloring.files.wordpress.com/2013/11/moon.jpg" alt="Moon"></p>

<amateur-observing>
Apparent size of M31
Mario Stefanutti
# Apparent size of M31

(Asked by: username_0 on 2013-11-27)

I am trying to understand something I read on wikipedia about M31.

Wikipedia says that M31 appears more than six times as wide as the full Moon.

But I remember that when I watched it naked eye it seamed a lot smaller, even considering that I was able to see only the central region. For this reason I also used the software Stellarium to check it and setting the same magnification for the two objects (see pictures), the wikipedia information still seems wrong ... or most likely I am wrong!

Where is that I fail?

"At an apparent magnitude of 3.4, the Andromeda Galaxy is one of the brightest Messier objects,[15] making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution. Although **it appears more than six times as wide as the full Moon** when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using binoculars or a small telescope"

![M31](https://4coloring.files.wordpress.com/2013/11/m31.jpg)

![Moon](https://4coloring.files.wordpress.com/2013/11/moon.jpg)

**Tags:** amateur-observing

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## 1 answers

### Answer by username_1 on 2013-11-27. Score: 11 | Accepted answer

The answer is right there in your screenshots. The 'dimensione' or angular diameter on the sky is 3 degrees for M31, whereas the moon has an angular diameter of only 0.5 degrees. In other words, M31 is about 6 times as wide as the moon.

As wikipedia correctly states, you need a large telescope to see the full extend of M31. With the naked eye of even a small telescope you simply cannot see the spiral arms.

I think this image shows it very neatly:
<http://apod.nasa.gov/apod/ap061228.html>


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