Caoimhín's Content

Today we are going to have a look ahead to the coming month. We are going to look ahead to June, which is the month of the summer solstice, but we’re not going to talk about the solstice itself too much just yet.

Just before we go all the way forward to June, we’re going to look ahead to the very end of May, which is not too far in the future now. We’re looking ahead to the New Moon, right next to the Sun during the day. At the moment, Mercury is also just next to the Sun during the day, so if you had the right kind of telescope, you’d be able to observe Mercury. By using a special telescope, or if you protect a normal telescope in the right way, Mercury is visible during the day through telescopes if it’s in the right location. It’s important to remember to never point your telescope directly at the Sun, and observing Mercury during the day is risky for this reason. The New Moon isn’t really going to be visible as it’s going to be an incredibly narrow crescent. In the middle of the day on the 26th, we’re seeing a waning crescent, 0.7% illuminated. Now we’re going to move forward to see if we can get the Moon less illuminated than this during the day, but this is already almost as new as the Moon is going to get for us here in Ireland. Following the Moon down to the horizon, it drops down to 0.4% and just before it hits the horizon, 0.3%. By sunset the next day, the Moon is at 0.8% illuminated, and it has crossed over to the other side of the Sun, it is now waxing. If we head back to morning time then that should go down. Just ahead of sunrise, the Moon pops up at just 0.1% illuminated. So we’re seeing the Moon newer on the morning of the 27th than we are at sunset on the 26th, but we’re not really seeing the Moon for either of those dates, because it is such a narrow crescent.

While the Moon is on the other side of the planet, over the Pacific, the Moon will be passing over the Sun. If we could look through the Earth then we could follow the Moon as it crosses from one side of the Sun to the other. This month, we would see that the Moon doesn’t exactly line up with the Sun, it kind of passes over the north of Sun instead. This is because the Moon is following our equator, and we’re a little bit tilted with regard to the Sun, so the Moon doesn’t line up directly with the Sun. This month it’s a pretty big distance, the Moon is pretty far from lining up with the Sun. Of course, we’re up here in Ireland, so we’re seeing things at a little bit of an angle already. Where the Moon appears relative to the Sun will vary depending on your location on Earth. This is why we don’t get solar eclipses every month, because the Moon can be pretty far from lining up with the Sun. It’s not just that it misses it by a little, it can be a good few degrees off in the sky. How far the Moon is from the Sun in the sky, that’s an angle we could measure, but I don’t think I will do it just yet, we’ll save that for another time.

Instead, we are going to continue to push ahead to the next Full Moon, which does bring us into June. We are jumping forward to the 11th to see the Moon at 99.6% as it’s rising. This gets up to 99.7% during the very short night. Usually I simulate what I would call a normal sky, I usually go with around Bortle Class 5 as the level of light pollution. That is roughly what I get in Cork City, not exactly in the city center. I can’t speak to exactly how dark the main street of Cork City is. I haven’t seen the sky from there at midnight certainly in quite a while, but I do know that close to the city center I see a sky close to Bortle Class 5. We can still see 100’s of stars if the sky is clear, we can certainly see Mars at the moment. Looking at the sky for the 11th, we’re still very close to the summer solstice, but we’ve also got the Full Moon, which makes the sky much brighter. The Moon seems to reach its fullest just after midnight on the 11th, so we’re seeing the Full Moon rise before midnight on the 10th. We’re seeing the Moon rise at just 10:20, it skirts over the southern horizon and then it sets just about 4 o’ clock. The Moon is barely in the sky at all, just 6 hours, and even for part of the time we’re seeing the Moon, the sky isn’t that dark. I would be hard pressed to call 10:30 in Junse “nighttime”, there’s still a lot of light from the Sun in the sky, this is certainly twilight.

In Stellarium, the Sun will list when twilight is when the Sun is selected. As the Sun sets the sky starts darkening, but we still see a little bit of sunset glow. The sky will continue to darken, but even at its darkest point, there’s still quite a bit of light in the sky and that is because we are so close to the summer solstice. Not only is the Moon only going to be visible for what seems like a very short amount of time, it’s going to be a very, very short night, if you can call it night at all. Technically it is twilight. The Sun in Stellarium lists various times along with the normal characteristics that Stellarium shows for stars. There is a time for morning twilight and evening twilight, a length for daytime and the times when the Sun rises and sets. This lets us see that the Sun is setting at just before 10 o’clock, this is the time that we’re getting for sunset. With the Sun just set, evening twilight is going to continue for quite a while. However, the sky remains bright after the time listed. We get some level of darkness around the time that the Moon rises, what would be considered nighttime by most people, but there are certain levels of brightness that are considered types of twilight. Civil twilight, nautical twilight and astronomical twilight are all different levels of brightness, and we do not get past astronomical twilight here in Ireland in midsummer. Twilight is as dark as the sky gets, and then the Sun starts to come up again. We’re seeing that sunlight certainly by 4 o’clock, and moring twilight is listed at 4:30. So we’re seeing the sunlight there at 4 o’clock even though it’s not Stellarium indicates morning twilight at 4:30.

It is likely that this is only accounting for civil twilight, the first level, but I can double check by moving into winter. We can compare to the winter solstice to see how twilight behaves then. Night time still isn’t being listed, but we can see that daytime lasts 7 hours 46 minutes. We can see that the Sun’s rising at just a little after 8:30 and our twilight is listed at just about 8 o’clock. Moving even earlier, there is definitely still some twilight, even though morning twilight is listed at 8. That is enough of an investigation for me to say that Stellarium is listing at presumably civil twilight, which is the kind of first rank of twilight before the street lights come on, and it’s ignoring nautical twilight and astronomical twilight. Nautical twilight is when you can pretty much see what you’re doing on a ship, on the deck of a ship. Moving even darker is astronomical twilight, when there is enough light in the sky that it would interfere with astronomical observations. True darkness does come in winter just a little later.

Moving from midwinter back to midsummer, we can see the daytime length increasing. It increases and reaches a peak where the day length is given at 16 hours and 43 minutes for midsummer. An almost 17 hour day is much longer than the 12 hour day we’d expect, and that 17 hour day is buttressed by hours of twilight. We can see there if we’re getting our sunrise at just a bit after 5 and our morning twilight is beginning at just a bit after 4, that’s already almost an hour of what I am saying is civil twilight. Nautical and then astronomical twilight are a whole other chunk of time. As such, the sky just isn’t going to get that dark. Unfortunately we are not going to get true night, for a little bit of time. Night time disappears from the Irish sky in May, and doesn’t return until nearly August. We certainly don’t get any nighttime for all of the month of June, we’re not going to get real nighttime. We’ll barely get astronomical twilight, slightly further north in Ireland astronomical twilight isn’t even reached for a could of days around the solstice.

Just before we entirely finish up, let’s come back to this month just to get the Virgo cluster of galaxies in a reasonable position in the sky at a reasonable time when it’s reasonably dark. I know that we’re looking out here, we’ll just grab any galaxy, it doesn’t really matter which one. We’ve got Denebola in the Tail of Leo and just to the east is Vindemiatrix in Virgo. Between these is a bunch of galaxies, and even just zooming in a little I’m already seeing fuzzy shapes. I want to go with one that’s easy to see for now. Going with one that looks nice, the Lost Galaxy of Copeland, is in the right area. It looks nice, which is of course a big consideration if you’re trying to look for something in the sky. Starting with gigantic binoculars, we can definitely see those galaxies, but with gigantic binoculars you’d expect to see them. Going down to a more reasonable binoculars, and the galaxies definitely look like smudges rather than distinct galaxies, but also definitely not stars. That’s just at a Bortle class 5, if we go to a Bartle class 3, they definitely look like galaxies to me. We could probably pull it off with even a smaller binoculars, even with the smallest binoculars that Stellarium will simulate, there are definitely galaxies visible. There was a commenter on a previous YouTube video who asked a question, what would those galaxies look like if you just had a binoculars in a Bortle class 3 or 4. I can now say that they will look at least like smudges, honestly you can kind of see the arms of the Lost Galaxy of Copeland. They are worthwhile targets, at least those ones, and Markarian’s chain. I mentioned Markarian’s Chain recently, and they actually look pretty good. So binoculars in a Bortle Class 3 or 4 looking at these galaxies, absolutely you can see something of interest.

I hope that you enjoyed this piece, if you did, please do like it. If you enjoy this kind of content, you can subscribe to this website and my YouTube channel. Most importantly, thank you very much for watching, hopefully I’ll see you back here next time.