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Is andromeda galaxy really naked eye?


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Relatively easy here (semi-rural), but only on really clear and dark nights.

At a site I visit quite a lot in the Indre region of France (one streetlight in the village, 50 watts and turned out at 23:00), it is easy; M33 can just be seen as well (by my old eyes) with averted vision.

Chris

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I can just about make it out vaguely in a dark site.

Old hands will know this but Ursa Minor is quite a useful constellation for seeing how dark your skies are, or how good your eyes. It has just about every magnitude between 2.0 and 5.0 in its main stars. Anwar is the faintest star at Mag 5.0 in the little square of Ursa Minor. I can see that in dark skies. There's a Mag 5.8 star right next to Yildun, a 4.3 magnitude star closest to Polaris. I cannot see that mag 5.8 star even in the darkest skies. Yet I can make out M31.

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I have decently dark skies here in NI, but not exceptionally so. Around mag +6.

M31 is an easy spot with the naked eye on any night it is up high enough in the sky. It would take a pretty poor night for it not to be easily seen. It's easy enough for example that I can show it to friends and family for the very first time and they too can see it without much effort.

I would say that M31 is about as easy to spot naked eye as the Double Cluster - perhaps a little less apparent. Easier than M35 though.

The absolute limit for my location and eyes is M33 (Triangulum Galaxy). Not because of it's magnitude but because of it's low surface brightness. It is right on the very edge of naked eye visibility here on the best of nights and very difficult to spot. Lot's of averted vision required just to sense it presence with the naked eye. I feel I've been able to see it  on the best nights but not in a way that I could state 100% for sure. In the scope I can see it's spiral structure fairly easy from my skies.

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A "dark" sky is one in which the Milky Way is visible. Anything else is bright. Most people live under bright skies.

M31 is a galaxy much like ours. So if you can see our own galaxy then you can expect to see our neighbour M31. In fact M31 is a bit brighter than the Milky Way, so M31 may be faintly visible even if the Milky Way isn't. If you can see stars down to about mag 5 then you should probably be able to see M31. To see the Milky Way you need a limit more like 5.5 or better.

The double cluster is a bit brighter than M31, and so may be seen with the naked eye even if M31 or the Milky Way aren't visible.

To see M33 you need a naked eye limit close to 7. Most people don't see fainter than about 6, even at an ideal site. Seeing M33 naked eye is a test of sky darkness and personal acuity. Many people claim they can do it, but I wonder how many really have.

Earth's atmosphere emits a constant, faint auroral light at all latitudes, and this natural "light pollution" sets a limit on what we see, even at the darkest site. In space, an average person should be able to see down to about mag 8.5, in which case M33 would be very clearly visible, and maybe M81.

The main reason why M33 is so much harder than M31 is  that it's smaller (because it's further away). If M33 were brought to the same distance as M31 it would be a little bit fainter in the sky, but still an easy object at a dark site. Indeed, the same is true for pretty much all the galaxies we look at through telescopes - they have roughly similar surface brightnesses (within a  certain range) and a telescope brings them "closer", makes them "bigger", until they're sort of like M31.

So if you can't see M31 naked eye you'll struggle to see other galaxies with a telescope. At a light-polluted site only the bright  central core of M31 is visible in a telescope (a smalll, disappointing, featureless blob), and the same is true with other galaxies. Making them "nearer" and "bigger" at a light polluted site tends to show only their cores.

If you want to go scuba diving you need an ocean, not a bathtub. If you want to see galaxies you need a dark site, not a bright one. Some hobbies, you just gotta travel a bit.

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The thing that's special about Andromeda being naked eye is that it's the only galaxy, out of all the gazillions of other galaxies out there, that can in fact be seen naked eye from Earth. The two things that help of course are knowing where to look, and, having a dark observing site. :)

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M13 is also naked eye from a dark site... I was pleasantly surprised on the Isle of Wight with21.4mag skies. Sometimes you need to little box to tell you how good or bad things are... Though it doesn't tell you about transparency... I watched the stars fade away.... Still very dark, but no good for observing. Go to a starparty to see what you are missing!

PEterW

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If you want to go scuba diving you need an ocean, not a bathtub. If you want to see galaxies you need a dark site, not a bright one. Some hobbies, you just gotta travel a bit.

This is so funny yet so so true.

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I can pick out M31 on a decent night without a problem.  Using Ursa Minor as a guide I've estimated NELM to be easily in excess of 5.5 on such occasions.  I've not managed to pick out M33 from home though I can't say that I've really tried that often, but the double cluster in Perseus is also usually fairly obvious on good nights too.

James

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Hi Pluto' thanks for the useful reminder of how fortunate I am (and no doubt many others) are to live under darker skies than yourself. Where I live amongst the Pennine hills there is plenty of weather (and some pollution) that often makes stargazing a pretty fruitless occupation BUT when it is clear, like last night, it is good.

Last night/early this morning intent on catching sight of the Perseids, I couldn't resist a look around with my just my 6.5 x32s and M31 and the Double Cluster were so easy and good to see. Putting the binos down to look for meteors I kept drifting back to M31 and knowing exactly where it was it I tried to convince myself I could see some fuzziness there with the naked eye but I wouldn't swear to it. Slightly better seeing would have made it more certain.

If you can ride to somewhere darker, your 20x60s, which give great contrasty views, will  show you much more.

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Some have claimed to see M81 / 82 naked eye - but I find that claim hard to swallow. Not just because they are much fainter but also much smaller.

I've seen M13 (Hercules Globular) clearly with the naked eye before... not from home however - rather from 4,000ft up in the mountains of Gran Canaria. But it was clearly visible with direct vision from there.

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I didnt mean posters on this site could have been exaggerating. It was mentioned in books I often read on astronomy. I dont think I realise just how bright my sky is. What I need to do is find a remote campsite and take my binos (I only ride a motorcycle). Low mag works best for nebula and galaxies anyway.

If you can't see the bottom star in Orion's sword you seriously have my sympathy :-(

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Definitely naked eye from my garden under okay skies (can just about see the Milky Way). I usually have to use averted vision. I reckon I could see it with direct vision under decent dark skies on hols in Dorset, where the Milky Way was stunning :laugh:  I also like catchiing the Beehive, M44, naked eye. I saw it naked eye before I realised it was the Beehive.

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My naked eye eyesight is poor but there isn't the slightest doubt about the elongated streak which M31 presents from our site. Not the slightest hint of a doubt about that. If I point it out to beginners with a laser many say, 'Yes, got it.' 

To put my unaided distance vision into context, my wife sees deer, foxes and boar in the fields which I can only see in bins. Sad!!!

Olly

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  • 3 years later...

Thread resurrection I know! However, I found this useful thread as a search answer to naked eye observation of M31.

I was searching for this as a result of scanning the skies on Monday evening (one of the few clear patches I’ve had recently) in my LP south-West London garden. Near full  moon was up.

Using my night vision monoculars with 685 filter at 1x, so naked eye equivalent. I wasn’t looking for anything in particular but just bumped into m31 looking huge - very significant extension either side. I was stunned how much it stood out in direct vision. NV is best on nebulae but it definitely gives you a great boost for galaxies as well. I do recall now on another evening a month or so ago also getting m110 with the night vision and my 3x lens.

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In my experience M31 is naked eye (averted vision) even from fairly light polluted skies. 25+ years ago I live at Staines, Mx (now Bortle 6 - I don't know what it was, as no Bortle scale back then) and later at Frimley, Surrey (Bortle 5 - SQM~19) and had no difficulty finding it with AV at both locations in a moonless sky. BTW M13 and the double cluster were also fairly easy targets for me at both locations. I now live in South Norfolk (Bortle 4/3 - SQM range 20.8-21.5 depending on seeing) and all 3 are easy in direct vision and on nights of excellent seeing I have also glimpsed M33 with AV, making that the furthest naked eye object that I have seen, beating M31 by a few hundred lys. Binocular and telescope views of M31 (and of course everything else) are a vastly improved experience from Norfolk than anything I experienced from ~50 years living in Surrey.

Dark skies rule....:thumbright:

Cheers, Geof

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With a dark sky and good eye sight it is possible to seeAndromeda.
Apparentlysome lucky people can see at least one of the satellite of Jupiter!

Unfortunately I don't have either, living in the S.F. Bay Area with plenty of light pollution and AMD, although I have no problem using averted vision..

A dark sky is primordial, with a very transparent sky.

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