Caoimhín's Content

Today, we are going to take a look at the late September sky, but for a change we are going to look at the sky from a lower latitude. I usually speak from the perspective of Ireland, and here in Ireland we’re pretty far north in the northern hemisphere. As we’re pretty high up on the planet, the sky looks different. It’s difficult to see the bottom part of Sagittarius, it’s difficult to see much of Scorpius, we don’t get to see the tail of the Scorpion for example. We’re missing Mars at the moment, even though it is a reasonable distance out from the Sun.

To change this, we’re going to take a look at the sky from a little closer to the equator. We won’t go all the way to the equator just yet, we’ll just come down a little bit, to about 37 degrees north. Immediately, the sky gets a little bit darker even though the time is the same. We’re not seeing as much of the sunset glow thanks to the steeper angle of the sunset. This lets us see Mars, a little higher in the sky. We’ve only come down about 15 degrees from our 52 degrees north in Ireland, and already there is a noticeable difference. We’re still looking at the same sky and we can see many of the same things. Saturn is still rising as the Sun sets, and the summer triangle is still nice and high in the sky. One thing that I definitely notice is that a lot more of Scorpius is visible, we can see the tail of the Scorpion towards the south. We can also see more of Sagittarius. If we push a little bit later, the sky does still darken little further. Sagittarius does have more stars above the horizon, if we get rid of the atmosphere for a second we’ll be able to see some of those other stars, but because of the extinction of the atmosphere they’re not very visible. They are still quite low in the sky, and they are also faint stars. This is all presuming light pollution, they would be more visible in the countryside.

For all of the locations, we’re looking at the sky around the date of the equinox. We’ll be looking at the 22nd and 21st mostly, also the date of the partial solar eclipse that’s visible in New Zealand. I won’t go over that again, I’ve gone over it previously on this website, but that is one of the events that’s happening around this time. As we come up to the morning time, all of the constellation Canis Major is visible, not just Sirius, but the lower half of the dog, which is still washed out or extincted from Ireland. It’s a lot more above the horizon from 37 degrees north. Venus is also visible further from the horizon, and if we come all the way up to sunrise, we should see the Sun rising directly in the east. The technical date of the equinox is the 22nd, at around 6pm UTC. Even if you are closer to the equator, the Sun should be rising pretty much straight out of the east on that date. That means it will set pretty much straight down in the west as well. Of course, we don’t always get to see the Sun as it’s touching the horizon, we often have some mountains or something in the way. However, the Sun will pretty much be setting in due west here on the 22nd. The date of the equinox does vary a little bit due to leap years, so the date varies, but of course that is just on our calendar. On these dates the Moon is very close to being in front of the Sun from anywhere, but the partial solar eclipse is only visible from down in New Zealand, not from here in Ireland.

We’re going to move a little bit more, we’re going to go closer to the equator. We won’t go all the way to the equator just yet, just down to about 19 degrees north. We’re still definitely off of the equator, but we are closer to it, so it’s again going to have a subtle enough effect, but still an effect, on what we see in the sky. Mars is visible in greater darkness at sunset because the Sun is almost going straight under the horizon. It’s not quite going straight down yet, we’re not at the equator, so there is still a little bit of a slant to the ecliptic. Nonetheless, Mars is higher from the horizon and visible when the sky is truly dark. Scorpius and Sagittarius are now both quite high in the sky, they’re farr off the horizon making them much easier to see if you have buildings or trees in the way. We’re far enough south to see the summer triangle practically at the zenith.

We’ll turn around to the north because we are now hitting a place where the Plough or the Big Dipper isn’t up for the entire night. Down here at 19 degrees north, we can see the North Star still above the North Pole and the horizon, but the Plough is completely under the horizon. We still have Cassiopeia up on the other side to help us find the north star, but if you’re looking for the Plough at certain times of the night on certain dates, even in the Northern Hemisphere, if you’re too close to the equator, you won’t be able to see it. The Plough will dip below the horizon, it stops being circumpolar. From this latitude, on other dates the Plough would be visible above or besides the North Star. Turning towards the east at sunrise, it’s almost visible how much straighter up in the sky things are going, especially the planets, even though we’re not quite at the equator just yet. Canis Major now gets quite high before the sunrise, and Venus visible in true darkness for quite a while. It takes a while to before the Sun’s glow is bright enough to wipe out Venus, and before they vanish it looks like Venus and Jupiter are almost going straight up into the sky.

Due to us being around the equinox at the moment, we’re pretty much at the time where the Sun is shining straight at the equator for both sides of the planet, we’re moving out of summer or winter on both sides of the planet. That means when we’re at the equator, the ecliptic should be pretty much rising straight overhead. We’re going to go a little south of the equator, but not by too much, just about 7 degrees south. Now the planets seem to be leaning a little to the north as they rise and set. We are after going south of the equator now, so of course we would expect there to be a little tilt to “other” direction. Where exactly we see the ecliptic in the sky does vary due to the tilt of the Earth, so where exactly we’re going to see it will change with the time of the year. Even though we are at the equinox, it doesn’t look like the planets are rising directly out of the east or directly out of the west, it still looks like there’s a little bit of a tilt going on. Of course, the planets don’t directly line up with the ecliptic either, there is a little bit of variation in the planets and how close they are to the ecliptic. Mars is now definitely significantly above the horizon as the Sun sets. It’s the same distance from the Sun, but at a steeper angle to the horizon. We can see that Sagittarius and Scorpius are significantly above the horizon and the Summer Triangle is practically in the northern sky.

The North Star is just under the horizon, so as we often do to take a look at things, we’ll get rid of the ground here. This lets us see the Plough pointing up to the North Star, so we can tell roughly where the north star is. However, even with the ground taken away, atmospheric extinction at the horizon is enough to block out the stars, so we’ll get rid of the atmosphere as well. That reveals the North Star pretty much dead on the horizon. It’s a little under the horizon because we are a little further south than the equator. While we’re the equator, we are going to move out into the countryside, because so much more of the core of the Milky Way is going to be visible. We can tell because we have more of those constellations showing us where the core of the Milky Way is, Sagittarius and Scorpius. We will get rid of all of the light pollution, and the galaxy comes into view. We can see a lot more of the core of the Milky Way, but we don’t see as much of the outer arms because we’re nice and close to the equator. Just after sunset the Milky Way is almost going straight up in the sky, but the Sun will be blocking it out while it is truly vertical. Once the sky darkens, we’re seeing the whole core of the Milky Way, we can see the core starting to tail away on the side we don’t see from here in the north.

That view will increase as we keep moving south of the equator, which we are going to do. We’re going to go further down, down to around 17 degrees south. We’re going to start seeing a little bit more of the glow of the Sun at sunset because the tilt is coming back just in the other direction. We’re still seeing Mars very clearly and also getting seen much more clearly we’ve got that glow of the Milky Way. We can see the whole core for sure with the Milky Way tailing away on either side. The Summer Triangle is now very much part of the northern sky. If we pull back to a very wide field of view, we can see Mars and Saturn on opposite sides of the sky. We can see them while we’re looking north. Now, the planets are kind of curving northward, that’s because they’re following the ecliptic and we’re now down in the southern hemisphere looking at the ecliptic from the other side. Saturn is almost at the zenith once we reach the middle of the night. If you are down at 17 degrees south, Saturn is going to look particularly good around its opposition because it’s going to be right in the middle of the sky, so you’ll be viewing it through the least amount of atmospheres. Neptune is right there as well, coming to opposition on the 23rd. Coming up to morning time, we’re seeing a lot of that outer edge of the Milky Way now, as the core portion has set. Jupiter and Venus are both kind of curving off towards the north, the same way from up here in the north, we see them curving towards the south, and that’s because of our perspective on the ecliptic.

We’ve been looking at the September sky for quite a while because there are so many interesting things in it, but I hope you enjoyed this different view. Maybe you’re always reading about a different perspective when you read these pieces, because you’re not at 52 degrees north, maybe you got to read about the sky a little bit closer to how it’s going to look for you in this piece. Whether you did or didn’t, I hope that you enjoyed it. If you did enjoy it, then please do like it. If you like this kind of content, then please do subscribe to this website and my Youtube channel. Thank you very much for reading and hopefully I’ll see you back here next time.