The biggest hurdle we face as backyard astronomers is finding objects that we want to see. You may have heard that the Andromeda Galaxy is the brightest galaxy in the night sky, so why is it so difficult to find?
Indeed, Andromeda Galaxy (which is also known as M31, for its inclusion in the Messier catalog) is the brightest galaxy, but it’s also 2 million light-years away and actually quite faint because its light covers a large area. In fact, the famous spiral galaxy is as wide a six full moons!
However, when you know where to look, the best time of year to view it, and the ideal conditions needed to get the best views, it’s actually quite easy to locate.
We’ll cover all of that in the rest of this article. To jump to a specific section, tap on it in the table of contents below.
When is the Best Time to Look For Andromeda?
The constellation of Andromeda is best viewed in fall and winter in the Northern Hemisphere, where it can be seen from dusk until dawn.
In late September and early October, M31 rises in the eastern sky soon after sunset and gains height until it’s overhead around midnight. It doesn’t set again until after sunrise.
The viewing window improves through winter, as the galaxy is high overhead at 8 pm in November, December, and January. By February, we need to be hunting for it earlier in the evening, and, in March, we lose the chance to see it because it sets soon after night falls.
Andromeda can’t be seen in April and May because it’s in the sky at the same time as the Sun, but opportunities to locate it soon return.
If you’re an early-morning astronomer, then late spring and summer offer great conditions for spying Andromeda. Look northeast in the early hours of June, July, and August, when it will be almost overhead at 4 am. Morning views continue to September, and the annual cycle begins to repeat.
To get the details of where to see the galaxy on any night of the year in your location, use a dedicated star chart, or astronomy software such as the free Stellarium or SkySafari 6, which you need to pay for.
Even when Andromeda is high in the sky, we still need good seeing conditions to get the best views.
It is a dim object, so is much harder to see when there is light pollution – including from the Moon. So always make sure that there is no Moon in the sky to ruin your view, and that you’re observing from the darkest sky you have access to.
This dark sky finder map (opens a new tab) is a great resource for seeing how dark your sky is and for finding your closest darker sites.
When you know if tonight’s a good night for viewing Andromeda, it’s time to find it.
Where is the Andromeda Galaxy?
You won’t be surprised to learn that the Andromeda Galaxy is found in the constellation of Andromeda.
The image below (from SkySafari 6) shows where the galaxy is in relation to Andromeda’s ‘legs’ extending from one corner of the Great Square of Pegasus. Note the constellation of Cassiopeia above the Andromeda Galaxy.
Click on the star chart image for a full-screen version.
Now you know where in the sky the galaxy lives, we’re going to show you two methods of finding it.
How to Find the Andromeda Galaxy With a Telescope.
Both routes to finding M31 use a method known as star-hopping. This is where we begin with an easily recognizable object and then use a series of steps, or hops, from there to our object.
In this case, we’ll first begin with the constellation of Cassiopeia, which is a very bright ‘M’ or ‘W’ shape that is always in the sky. Our second route is to use the Great Square of Pegasus and two bright stars in the Andromeda constellation to hop to Andromeda Galaxy.
Finding Andromeda Galaxy From Cassiopeia
Cassiopeia is perhaps the easiest constellation to find in the night sky after the Big Dipper, which makes it perfect to use for hunting our target. For most of us, it’s also a circumpolar constellation because it’s near the north star, which means it’s visible all night and a reliable sight.
The image below can be clicked for a full-screen version. It shows that the ‘V’ shape formed by the stars Navi, Shedar, and Caph point the way towards Andromeda Galaxy.
This route can be made more reliable. Draw an imaginary line (shown in orange) roughly joining the stars Kappa Cas, Shedar, and Zeta Cas, and extend it towards the bright star Pi Andromedae. The galaxy lies 3/4 of the way along this line from Shedar.
In practice, the easiest way to find Andromeda using this route is to point your telescope (or astronomy binoculars) at Shedar and follow the imaginary line south. It will be very clear when you’ve stumbled upon the galaxy.
For the best chance of success, make sure to use low magnification and a wide field of view.
Finding Andromeda Galaxy from the Constellation of Andromeda
The second star-hopping route begins at a place that is slightly harder to pick out than Cassiopeia but is much closer to the galaxy itself. We’re going to start by identifying the Great Square of Pegasus, which will lead us to the constellation of Andromeda, and on to the galaxy itself.
The Great Square of Pegasus is a famous site in night skies and is highlighted in orange on the image below. Note the location of the constellations of Cassiopeia and Andromeda and Andromeda Galaxy.
When you’ve located the square, the next step is to find the star Alpheratz on the corner nearest the ‘W’ of Cassiopeia. Emerging from Alpheratz are two ‘legs’ of bright stars, these are the constellation of Cassiopeia.
Travel along the bottom one, i.e. furthest from Cassiopeia, until you get to the second bright star named Mirach. In the leg above, there’s a corresponding bright star Mu Andromedae (shown as ‘Mu And’ on the image below).
Follow the line from Mirach to Mu Andromedae. Continue in the same direction for about the same distance you’ve already traveled and you will land at M31.
Full details are shown in the SkySafari 6 image below, which you can click to give a full-screen version.
The galaxy is only 1.3° away from Mu Andromedae, which is close enough that you will be able to see both objects in your viewfinder at the same time. You may even get them both in your eyepiece if you have a wide field of view and low magnification.
What Andromeda Galaxy Looks Like in a Telescope
One of the hardest things about locating the Andromeda Galaxy for the first time is knowing what to expect when you see it.
It sadly won’t be anywhere near as large, bright, and crisp as the image below, and it’s nowhere near as bright as the stars nearby.
It is the most distant object visible to the naked eye, but it only appears as a hazy patch of light in the sky, about as wide as the full moon would be. You won’t be able to see it at all if you live in the city because of light pollution.
Binoculars will reveal more detail; you should be able to see that the core is more ‘solid’ than the outer, and you’ll certainly see more than your eyes alone can reveal.
For a more detailed view, you’ll need to use a telescope. The more light you can gather, the more detail you see, meaning larger scopes designed for deep space viewing give better results. However, any telescope will reveal the mist of stars in M31 if you have a dark sky.
If you can, try and get away from light-polluted areas, which will obscure the edges of Andromeda and leave you only able to see its core. Light pollution includes moonlight, so pick an observing time when the Moon is below the horizon.
Andromeda in a Small Telescope
In any scope of 4″ and upwards, you’ll see an oval-shaped blur that’s long and thin. With averted vision and patience, you’ll notice the oval is thicker and brighter at its center.
The companion galaxy M32 looks like a too-large star nestled just south of the main galaxy. If your scope will tolerate higher magnification, you may see that M32 is also more oval than circular.
The main galaxy may yield tonal changes in its brightness away from its heart. You may also perceive it to be more circular at its heart and flatter, more linear further out.
It’s a push in a smaller scope, but challenge yourself to see dust lanes against the light regions.
Andromeda in a Large Telescope
If you own a large Dobsonian scope, you’ll be blown away by the sight of Andromeda.
Allow your eyes to adapt to the faint light and, if the night is dark enough, averted vision will help you discover the wider reaches of this mesmerizing vista.
Looking through 8″, 10″, or more, you’ll be able to chase the circuit of ghostly arms of stars surrounding the brighter central core.
What is the Andromeda Galaxy?
The Andromeda Galaxy is a member of the Local Group of galaxies, the same group that our own Milky Way galaxy is in.
When we look at this spiral galaxy, we see it almost edge-on, tilted as it is at just 13° to our line of sight. It is believed that M31 mirrors the structure of our galaxy in many ways, making it a useful study for scientists.
We think the galaxy is over 140,000 light-years wide and is over 2.5 million light-years away from Earth. The number of stars in Andromeda is thought to be one trillion! A mind-boggling number, and about three times more than we have in the Milky Way.
Andromeda has four dwarf galaxies nearby. The most famous two companion galaxies are M32 and M110. You can see them both as large, bright ‘stars’ on the image at the top of this page. The smaller one above Andromeda is M32, while M110 is larger and below the main galaxy.
While M31 is the brightest galaxy visible in the northern hemisphere, it can still be hard to find.
With the information in this article and access to a decent star map, you should be able to find Andromeda Galaxy quite easily.