Caoimhín's Content

Today, for this issue or installment, I decided to take a look at the sky from a couple of different locations and compare the kind of view that you can get. This is something that I regularly do as the sky does look from different places. Often, my focus is on comparing dark skies to light polluted city skies, or the timing of events like eclipses or conjunctions. This time however, it really is about what stars you can and can’t see. Of course, if you go from the South Pole to the North Pole, you’ll get a very different view, but that’s not the easiest thing to do. If you are limited to following roads, how far you can go will be limited, and how limited you’ll be will depend a lot on where you are, so that is our focus today.

Starting with the most familiar example to me, we begin with roughly what can be seen from Cork City in the South of Ireland. To keep the view consistent, the atmosphere has been removed, so we don’t have to worry about varying levels of light pollution. Looking at close to a midnight sky, Scorpius and Sagittarius are among the most recognizable constellations, right on the horizon in the South. These constellations are so low here at this time of the year, parts of the constellation aren’t above the horizon at all. The tail of Scorpius is dipping down under the horizon here, along with parts of Sagittarius. The Summer Triangle is reasonably high in the sky, as it should be given the time of year. It’s about halfway up the sky, or at least roughly the center of it is. It’s definitely not at the zenith, though the very top of the triangle looks like it will cross the zenith a bit after midnight. Along with some of the middle of the Milky Way low to the South, those are some of the most prominent things that we get to see from here in the South of Ireland. If you were to travel all the way to the north of Ireland, the view would change very slightly. Going to the North of the Island of Ireland doesn’t necessarily require travelling from the Republic of Ireland to Northern Ireland, so international boundaries don’t necessarily need to be crossed. Donegal reaches right up to the north of the island and is in the Republic, but in order to use an easy to find location, I do shift the view into Northern Ireland, specifically Armagh Observatory. Armagh Observatory does have a public exhibit, making a good place to visit in real life as well as a good location for our comparative purposes here. Taking a look at our map coordinates, we’ve moved by a whole 2 degrees of latitude, we were at 52 degrees North now we’re at 54 degrees North, and that is only enough for a rather slight difference. Antares, the brightest star in Scorpius, is definitely closer to the horizon there, but it still hasn’t sunk under the horizon. We lose a little of the Scorpion, but even in the South we only see the top and front part of Scorpion. We’re not able to see the tail in either location, we’d need to move further South to bring that into view. The summer triangle is still visible and still in a similar position, about halfway up the sky. Again, it is a big constellation, and given its location far from the reference point of the horizon, it can be tough to tell that it has moved when the difference is so small. The difference is measurable, but an easier shift to measure is visible looking North. Turning to the North, the Plough will of course be visible, as will the North Star. The North Star is practically right above the North Pole, or 90 degrees North. If you measure the angle from the horizon to the North Star, it will give you your latitude here on Earth. By moving 2 degrees higher on the planet, the North Star will be about 2 degrees higher in the sky, but this is usually a difference that you would need to measure, it’s tough to see with just the naked eye.

That little of a difference is the most you can do in Ireland. Without getting on a boat to mainland Europe, or north to the Arctic, this is the most that I can change my sky. That is of course mostly due to Ireland being an island, but international borders can also be an impediment to travel, forcing this kind of limit on many countries. Larger countries will then offer a greater chance to change your view of the sky without leaving them. Going with the United States of America as an example, it is a bit wider in longitude than it is tall in latitude, as is Russia over here, but they are still taller than Ireland. To stick with one country, I have limited the change to the contiguous United States. Heading from Florida to Alaska will give you an incredible change in the sky, especially if you head to an area that is free of light pollution. Limiting ourselves to land travel within one country, we’ll head up towards the Great Lakes. The border with Canada gets a little wiggly and at times complicated here, but it is a bigger target to aim for than the top of Maine. From this new location, we can see clear differences with our view from Ireland as well. There’s a lot more of the tail of Scorpius visible and we’re seeing under Sagittarius. More of the galactic core or nucleus is visible. Even the most northern part of the United States, other than Alaska, is still further South than the South of Ireland such as Cork City. This also means that in the morning you would see the planets a little bit easier, particularly Jupiter which at the moment is still quite close to the sunrise. We’ll stick with a midnight view for our comparison here. If you were to be in the North of the United States with this as your sky, you could hypothetically hop in a car and drive all the way down to the South. I know it’s not quite that easy, driving such a long distance itself is pretty taxing, and it would require having a car and being able to drive, but there is public transport. Technically, it is possible to go from the Great Lakes Region all the way to the Louisiana by water, but in practice I’m sure it’s far from the easiest option. From a more southerly portion of the United States, the sky will be noticeably different from the North. Looking south, Sagittarius and Scorpius are considerably above the horizon, almost halfway up the sky. We’re seeing the whole tail of the Scorpion perfectly, comfortably above the horizon. With the lines of the constellation visible, you can see that there are whole constellations visible that would be out of view from the northern United States. Pretty much the whole core or nucleus of the galaxy is visible above the southern horizon. Just under the horizon it would start tailing away into the other arm of the Galaxy. It should be clear the the difference between these locations is significantly more than the biggest difference you could get while staying within Ireland.

The United States isn’t the only place that offers such dramatic change in the sky, other locations with also give you a good opportunity to do stuff like this. Heading further south, aiming at Chile lets us start a bit south of the equator. Given the map that I use for picking a location, there is a good chance that I actually ended up in Southern Peru, rather than Northern Chile. In the video I blame the quality of the map, but if I was a bit better at geography it would probably be less of an issue. Chile is a good example due to its length, reaching from about halfway up the continent of South America all the way to the bottom, Chile affords the chance of drastically changing latitude, and thus your view of the sky. Given that this is in the Southern Hemisphere, it will already be a very different view of the sky. With a location close to the equator, we can see the whole core of the Milky Way with arms stretching either side, the whole way across the sky. Trying to keep the view as similar as possible, we’ll face roughly South, with one arm of the galaxy crossing the horizon almost in the South. One of the main things we get to see are the Large and Small Magellanic Clouds. As I’ve mentioned previously, these objects may be renamed in the near future. We have Sagittarius and Scorpius really high in the sky now. We can also see the Southern Crown, a small curve of stars, not quite a ring but more like a C shape. Seeing constellations with names featuring the descriptor Southern is a good hint that you are looking at the Southern Hemispheres sky. It’s proper name is Corona Australis, meaning the Southern Crown, compared with Corona Borealis, the Northern Crown, which we see in the Northern Hemisphere. I’ll give a reminder here that that constellation, the Northern one, is where we expect to see a supernova in the very near future. I have a whole piece and video about it further back in the archives. One of the best things about this view is the galactic core, with the heart of the Milky Way dominating the sky, rather than either of the arms. You need a lack of light pollution to achieve this view, but that is easier to achieve in places like Chile, simply because of the mountains and the forests. This can help with light pollution, given that this pollution is caused by human light sources. The more buildings around, especially large collections of buildings like cities, creates the worst light pollution. In rough terrain, especially high up in the mountains, it’s tough to build large things that create a lot of light. It’s particularly difficult to build a large city high up in the mountains, it’s easier to do those things lower down on slopes, partly to make it easier to trade and access goods. In regions where you do have a lot of mountains, there are several benefit when it comes to astronomy, especially naked eye astronomy. Not only will they give you a good view of the sky because there shouldn’t be too many buildings around, but they’re also quite high, you might get a slightly clearer view of the sky especially if you’re above some of the clouds. The mountains can act almost like shields, blocking light from neighbouring cities, so even if you are down in valley surrounded by mountains, you might still see benefits in the form of less light pollution ruining your view. However, this is meant to be about differences in latitude, so we’ll drop all the way down to the bottom, down to Tiera del Fuego. Moving down to the very bottom of the South American continent gives us a whole different view again. Further from the equator, we’re after losing the more northern constellations, and the ones left look upside down now. We can still see the Milky Way, with the core still being pretty high in the sky. Looking at the midnight sky, we’re seeing the core of the Milky Way practically in the North, rather than the South, as we’ve crossed to the other hemisphere more completely. Scorpius and Sagittarius are now upside-down as well compared to what we’re used to, but they are still both completely visible. We’re now seeing mostly the other arm of the Milky Way, the one which would be fully below the horizon from the Northern locations we’ve visited. The Large and Small Magellanic Clouds are now a lot higher in the sky, making them even easier to see. Almost all of the the summer triangle is out of view as well, we’re only seeing Altair. Deneb and Vega are way under the horizon from this view, at least at this time of the year. The difference seems even more extreme than the difference in the United States, but of course this is also an unfamiliar sky given that it is in the other hemisphere.

Given that I’ve shifted the view so far over the course of the video, I’m sure you can see that if you travel between different countries, if you’re willing to cross international borders, then of course you can get even more extreme differences in what’s visible in the sky. The further you travel in latitude, especially if you cross the equator, the greater the difference in what you get to see. Without travelling between countries, a tall country is what is required, Brazil would also be a good example of a tall country that affords a big change in sky from North to South. The key is changing latitude in particular, as changes in longitude won’t change what you see, but mostly when you see it. This can be useful for catching conjunctions or eclipses, but for the stars themselves, not much will change. A good example appears to be Russia, which is significantly broad in longitude, rather than tall in latitude. As mentioned, still significantly taller than Ireland, and due to quirks of the Mercator projection, it can be hard to directly compare to the United State. Regardless, if we are looking at longitude, it certainly provides a large potential change. Starting in Western Russia, just over the border from various European countries, we will continue to look South at midnight. At about 54 degrees North, the sky is similar to Ireland, practically identical to the Northern Ireland location we’ve used. The Milky Way is visible, with its core crossing the horizon, Sagittarius and Scorpius are reasonably low to the horizon, hiding the Scorpions tail just as it is hidden from Ireland. If we then travel the whole breadth of the country, one thing that changes is the time zone. Moving back into night time brings the Milky Way up again, and it’s basically the exact same, because we haven’t changed our latitude we’ve only changed our longitude. To do this, I shifted to the Kamchatka Peninsula, as the very Eastern most portion of Russia, up by the Bering Strait, is substantially further North than the position we started with. Even changing the longitude as much as you can within one country, the sky doesn’t change half as much as it would with the same change in latitude. If you can change your latitude significantly with comparable ease, especially if you can just hop on a train or a bus without even changing country, then I encourage you to give it a shot.

Of course, if you are in a smaller country like me, or find yourself unable to travel, then I hope you now have some idea how much the sky can change and what it might look like. If you enjoyed this description then you might like some of my other write ups and videos, and you can catch the next one by subscribing to this website or my YouTube channel. However you find your way back, I hope you come back here again next time,