Caoimhín's Content

Today we are going to take a look at the winter night sky very generally. We’ll start just around sunset in early December, but we’ll go through the night and across a few months around midwinter. As we’re going to be taking a general look at the night sky, we’re going to ignore the planets and the Moon.

I’ve already mentioned where various planets and the Moon are going to be this December, 2025, but in other years the planets would be in different positions on the same dates, as would the Moon. The stars however would barely changing position. They would seem to change position a little, if we stick with the same date, but that’s really down to a quirk of our calendar. Every few years, the stars would seem to jump back, and then drift forward again, never really gaining or losing ground overall. The reason the stars change position in this subtle way is to do with leap years and the awkward length of our year. For a given date, things will drift a little bit out of position as our 365 day calendar drifts out of sync with our 365.25 day orbit. Then that drift is fixed again with the leap year, by the addition of the leap day, we get back on track.

Instead of talking about what’s visible from a smaller city like Cork, we’re going to look at a sky that’s slightly worse, more like a large city. It is a little bit of a worse view, but it may be a more realistic and common view. I do want general view of the sky, so we’re moving from Bortle Class 5 down to 8. While we’re at it, we might as well make the Moon a little bit smaller. The Moon of course, looks a little bit bigger to the naked eye than it really is. You can test this by looking at the Moon through a ring made by your fingers at arm’s length, or by looking at it upside down. The light of the Moon around the Moon, it’s halo, also makes it seem a bit bigger. By removing allowances for those effects in Stellarium, it makes the Moon just a little bit smaller, a little bit less obtrusive. The Moon changes position every year, so we can ignore it this time.

Taking a look at the very early evening sky, starting at just 5:30, which is really before a lot of people would start stargazing, there are already bright stars in the sky. The summer triangle, which of course is with us all summer, is still there at sunset even in December and January, but only around sunset and already in the west. We’ve got the Square of Pegasus roughly in the south, with us for most of the night. With the on going glow of sunset and the light pollution, we’re not quite seeing all of the square. If we wait until later, when it’s a little bit darker, the lower southeastern corner star, Algenib, is still a little bit tricky to see with this amount of light pollution. However we can see the other parts of the Square of Pegasus and the way it tails along into Andromeda and out towards Perseus. Cassiopeia is nice and clear, during the wintertime it’ll be pretty close to the zenith, early in the night it’s high up above the North Star, which makes it that little bit easier to see.

Turning around to the north, the Plough is under the North Star, and again, this is something that holds up through various years. If we go through various years, we’ll see the level of darkness changing thanks to the changing phases of the Moon. Also, there’s a little bit of a wiggle in the stars as we go to and from leap years. Other than that, we’re still seeing those same stars in those same positions every single year during this time. Thanks to the night sky starting so early in winter, even going from the sky in December through towards January, the summer triangle is still up at sunset, even if it is further over to the west. The Square of Pegasus will also be a little bit to the southwest in January, but still up at sunset. By then, Orion will be up in the early evening rather than closer to midnight. Due to the nights being so long and dark during winter, there’s plenty of time for things to come up. Coming back even closer to the start of December, if we wait till just a little bit later, Orion comes up. We’ll get all of Orion and the star Sirius into the sky before 11 o’clock, close to just 10:30.

We’re still seeing these same constellations over a lot of winter, but we’ll be able to see them earlier in the evening once we’re through to January. With the sky getting darker as we come through December, seeing most of the same constellations in true darkness is going to be achievable in December and January. Although the January nights are getting shorter, we’re still moving around the Sun and changing what stars are visible in the sky, bringing the morning constellations up quicker. Speaking of the constellations, the constellations are going to stay the same every year, they’ll be in the same places, even if the planets change position. In Stellarium, it’s even easier to see with the pictures themselves displayed that everything is going to stay the same, and has been the same for thousands of years, in terms of the positions of the stars and the constellations. It’s only the planets and the Moon that we really need to worry about.

Even with some light pollution, the more visible constellations, like Pegasus, Andromeda, Orion and Gemini, they’re nice and clear, even without the pictures in the sky, we can still see enough of the bright stars to map out those constellations. Even constellations that are a little fainter, like Auriga towards the east, it has a pentagon shape that is recognizable and Capella, one of it’s corners, is a bright star. Taurus can also be found, even though it’s difficult to see most of the Hyades and it’s tough to see the Pleiades, Aldebaran is still visible. Also, we know that Taurus has to be there because it’s right next to Orion, and Orion is very obvious once it’s up. As you get used to what constellations are near each other in the sky, you cam use them to find each other. For example, there are two reasonably faint stars west of Taurus and about as high at this time. They on their own are the whole visible part of the constellation Aries in these conditions, but you can still find it. This is something that you can tell because it’s next to Taurus. Even though it’s very hard to see the stars in Aries, you can tell where it should be. Even though most of the stars in Pisces are invisible at this level of light pollution, it’s whole part of the sky looks empty, we know that Taurus, Aries and Pisces are all in a row, so we know where the constellation has to be, given the position of the other constellations that are easier to see.

Staying up all night long and looking at the sky for the entire night can be a bit of a big ask. However, taking a look at the morning sky during the winter, even getting up early enough to see the sky while it’s still dark, is that little bit easier. We can ignore Mercury and Jupiter, which are there in 2025, but the planets keep changing position. We can depend on Leo nice and high in the sky, with that kind of almost trapezoidal shape. Now that we’ve come around to morning time, it’s the Plough that’s up nice and high and Cassiopeia is down low on the other side. They’ve almost swapped places, with that rotation of pretty much halfway around, from one side of the sky to the other reflecting our rotation, because it’s been almost 12 hours, half of the 24 hour rotation that we go through. Also up in the morning is Arcturus here, the brightest star in Boötes, and you can almost see it’s kind of kite-like shape even in a city sky. As I’ve mentioned in many videos, especially at this time of year, we can follow the Plough’s arced handle to Arcturus and then spike on to Spica and find Virgo early in the morning. Spica is still low in the morning, but bright enough to be seen. With Virgo and Leo on one side and Gemini still visible more to the west, this is another time when if you know the order of the constellations you know that we’re missing one. We’re missing Cancer the Crab, which isn’t visible at this level of light pollution, but it has to be there between Leo and Gemini.

If you are going stargazing, it is well worth heading out to the countryside. In winter time particularly it could be colder, especially if you get a nice clear sky. Going from a Bortle Class 8 sky down to Bortle Class 1, immediately there are around ten times more stars visible in the sky. With so much visible in the sky, some constellations can even be trickier to spot. Looking again at the December sunset, the summer triangle is bright enough to stand out against to surrounding stars. As the Sun is going down, those will still be the first stars to come out. In the countryside, starting your stargazing earlier can be even more useful because you’re going to see more earlier in the night. This also limits you to the brightest stars, which makes some of the shapes of the constellations more obvious. The summer triangle of course, but the Square of Pegasus is fully visible at just 5:30, in a way that it never is at any time from a Bortle Class 8 sky. Following the Square of Pegasus through Andromeda, the sort of fin-shape of Perseus is very obvious. Continuing east the pentagon of Auriga with the bright star Capella is also clear.

Moving even an hour or so later, the sky darkens quickly and all the fainter background stars fill in the sky. The summer triangle’s corners are still nice and bright, not too hard to see, whereas shapes like Perseus, they are getting a little bit trickier to see. Parts of Andromeda, even the Square of Pegasus, there are some other bright stars around them that can make things confusing. Taurus is certainly visible even early in the evening once we’re in the countryside. If we were back in the city, the combination of light pollution, the light from the Sun and how low the Hyades are in the sky makes them much more difficult to see. Aldebaran is visible, but we can’t see the whole Hyades. Out in the countryside, it’s a very thing, we can see the whole of the Hyades pretty much immediately, as soon as it starts to get dark, just about 5:40. There’s still a glow of sunlight in the sky, but it’s already dark enough to see those things.

If we move ahead towards midnight, the sky will get a little bit darker and Orion comes up nice and high in the sky. The bright star Sirius is always going to be visible, and even Procyon higher up in Canis Minor is distinctly bright, enough to be seen with light pollution. However, seeing the stars associated with Canis Major besides Sirius can be harder. Although there’s not much extra stars associated with Canis Minor, it is all visible. Even the stars that are associated with Cancer, are visible. With Cancer the Crab in particular, it doesn’t have a very distinct shape. With some of these other constellations, like Gemini and Leo on either side, they have a recognisable shape, even if they didn’t have bright stars. We don’t get quite so much of an obvious shape from Cancer the Crab. Looking back westward to Aries, the few stars that make up Aries are nice and bright, but surrounded by similarly bright stars. You can also just about see the kind of V-shape that makes up the base of the constellation Pisces, but it’s still very faint. Those stars can still be difficult to pick out even with a perfect level of darkness.

Pushing all the way forward to morning time, we’ll get a better view of Virgo and Boötes. With Boötes up reasonably high it’s easier to see the kite-like shape stretching northeast from Arcturus. Just east is Corona Borealis, which is a lot more obvious in a dark sky. Its curved shape can be tricky to spot if there’s a lot of light pollution but once we’re into a darker sky it becomes obvious. A little further east again is the trapezoid shape of Hercules. The body of Hercules is fairly easy to see, but the arms and legs of Hercules, along with the heads of the snake and everything that stretches out around Hercules, those parts can still be a little bit tough to see, even with a very low level of light pollution. Below Virgo is the kind of diamond-y shape of Corvus the Crow, which is much easier to see once we’re in the countryside. It is quite low in the sky, which doesn’t help, but it is just past Spica. If you follow the arc to Arcturus and spike on to Spica, then Corvus is just out the other side, and it’s a fairly easy to spot but lesser known constellation.

Despite the fact that Spica is very obvious, the actual shape of Virgo is very abstract, so it can still be pretty difficult to spot. Once you have some familiarity with the zodiacal constellations that wrap around the sky in this regular pattern, they can help you remember what constellations are supposed to be next to them. Hopefully, this will give you an idea as well as to the different kind of difficulties you’ll face in the city, where the bright stars are obvious but the only ones visible, and the opposite in the countryside, where there’s so many stars that some of them might blend together and get more difficult to see.

I hope you get to see the winter time skym I hope you get to do some stargazing over the course of the winter. I hope you get to see the sky with a good level of darkness in particular. If you enjoyed this piece, please do like it and if you like this kind of content then please subscribe to this website and my YouTube channel. Thank you very much for reading and hopefully I’ll see you back here next time.