I am living in the northern hemisphere in Greece and in class 4 area (light pollution scale). Is it possible to see the Andromeda galaxy with a naked eye?
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$\begingroup$ Young eye or old eye? By age 60 your magnitude limit goes from ~7 to ~5. $\endgroup$– Wayfaring StrangerCommented Aug 9, 2018 at 15:57
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$\begingroup$ Nice question! Based on it, I've just asked What is “class 4 light pollution” and could I estimate my own area's class visually? If the answer there refers to the scale you are using, you might consider adding that information to your question, since it will be informative to future readers. $\endgroup$– uhohCommented Aug 10, 2018 at 12:11
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Assuming you mean Bortle class 4, then the Andromeda galaxy (M31) should be a fairly easy object with the naked eye. It won’t be particularly impressive, but rather will look like a hazy blob. On the other hand it is more than 2 million light years distant, so it’s impressive to be able to see it at all.
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1$\begingroup$ And some people mistake the Andromeda galaxy for a star, just to give an idea of what kind of "hazy blob" we're talking about. $\endgroup$– called2voyage ♦Commented Aug 8, 2018 at 14:52
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$\begingroup$ The question refers to the level of light pollution "class 4 area (light pollution scale)" and this answer might suggest what scale that might be. Any thoughts if the OP's environment would be good enough? $\endgroup$– uhohCommented Aug 10, 2018 at 12:16
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$\begingroup$ @called2voyage take a look at the image here: gizmodo.com/… Andromeda is pretty big! See also commons.wikimedia.org/wiki/File:Andromeda_constellation_map.svg $\endgroup$– uhohCommented Aug 10, 2018 at 12:19
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1$\begingroup$ @uhoh You can't see that with the naked eye. This article has the original picture before the enhancement. You can only see Andromeda's core. $\endgroup$– called2voyage ♦Commented Aug 10, 2018 at 16:45
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$\begingroup$ I can dream, can't I? ;-) I remember seeing a faint fuzzy patch a zillion years ago back when I lived away from city lights. But I think if someone's vision were bad enough that stars were as large as even the core of Andromeda, they probably couldn't see many stars at all. Hmm... How bright is Andromeda's center, in magnitudes per square arcminute or something similar? $\endgroup$– uhohCommented Aug 10, 2018 at 17:20
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Yes, you can see Andromeda with the naked eye, assuming you have a site with suitable dark skies. Under good seeing conditions, you should be able to see it as a bit of a small hazy area using averted vision even in suburban skies.
Going a bit further out to a site with a good dark sky, you should be able to see it when looking directly at it.
Greece is (approximately) located around 40°N to 36°N in latitude. Andromeda galaxy is at +41° declination (approx).
Using this information, you can see how high it will rise in the sky (in the best scenario) which is important because if it is too low on the horizon, it will be extremely difficult to see. By using the formula (90°-latitude)+declination, we can see that Andromeda Galaxy will get to just over 90° from your horizon, (at the best case, being in the Northern part of Greece)) which means it will be almost directly overhead! Obviously, this is an approximation because the earth does have an axial tilt! Either way, this shows that it will get far clear of the horizon, meaning less atmospheric distortion. Of course, it would be best to do it when it is 90° above the horizon during the night time!
Download one of the many free apps you can get on your phone which will tell you the best times to view it.
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$\begingroup$ The question refers to the level of light pollution "class 4 area (light pollution scale)" and this answer might suggest what scale that might be. Any thoughts if the OP's environment matches your "suitable dark sky"? $\endgroup$– uhohCommented Aug 10, 2018 at 12:14
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1$\begingroup$ @uhoh Yeah, the Bortle scale is the only one that uses 'class' skies. Other scales use limiting naked eye magnitudes too, but unfortunately that can differ from person to person. Peoples views on what scale their night sky is can be subjective. Some people may class their skies as Bortle class 5, yet another person in the same location can say its more like a class 4 to them. Its a difficult thing to define. Hence why I said suburban skies, which is usually around the Bortle class 5. $\endgroup$– MCGCommented Aug 10, 2018 at 12:36