Caoimhín's Content

Today we are going to review a couple of the events that are happening at the end of September. We are starting with the equinox on the 23rd, but we’re also going to take a look at the opposition of Neptune on the 25th and the Full Moon on the 26th.

The date of the equinox is the 23rd of September this year, and we’re seeing the peak midday Sun at 1:24 pm, at UTC +1. This means if we were using UTC, it would be 12:24 rather than 13:24, that’s the extra +1. This isn’t the time of the equinox. It’s not the time that the equinox is occurring. If we move back to our sunrise here in Ireland, it is around 7 o’clock in the morning. The Sun is just crossing the horizon at about 7:25, but of course we know this is an illusion. If we got rid of the atmosphere, the Sun would be below the horizon at that time. This also isn’t the moment of the equinox, at really 06:26 UTC, this isn’t when the equinox is occurring.

The equinox is occurring at just about six minutes past midnight on the 23rd. We’re going to move all the way back to 00:06. At a few minutes past midnight we are into the 23rd. This is the moment of the equinox, according to the dates and times that I looked up, this is when the equinox is actually occurring. This is the moment when the Sun transitions across the equator, going from shining more on the north for our summer to more into the south for their summer, and of course the Sun isn’t up for us here. Really, we are at 00:06 UTC +1. We need to move ahead because we are at UTC plus 1, so 1:06 in the morning this is closer to 00:06 UTC. This is really the moment that the equinox is occurring. If we wanted to have the Sun in the middle of the sky for this moment, we would need to be at a location that’s more like UTC+12, so that we’re seeing UTC 00:00 when locally it’s 12:00, or midday.

Now, luckily, I happen to know a place where the time zone is UTC +12, way over in the Kamchatka Peninsula. We are going to go to the Kamchatka Peninsula, to the largest city on the Kamchatka Peninsula, Petropavlovsk-Kamchatsky. That puts us at a local time of UTC +12. However at 12:07, the Sun isn’t at its highest location in the sky. We would need to move forward a little bit, we’re still a little bit off, but this is closer to the actual time of the equinox, when the equinox is actually occurring. Of course, this happens for us here in Ireland, at 00:06 UTC, and that time happens for everyone all over the world, but the local times vary thanks to our local time zones. So seeing the Sun at its peak when the equinox is actually occurring, to see that, you would need to be in the east bordering the Pacific Ocean. That’s one of the reasons why, in a previous piece when we were at the hypothetical Null Island, we weren’t able to see the Sun exactly crossing the equator at this time. Coming back to Ireland puts us at 2:30 in the morning. There’s definitely something strange happening with the time zones. We would probably need to look for UTC +11 to account for the fact that there’s a +0, but I won’t get into those details here. We have other things to look at and one of them is Neptune.

We’re going to move ahead to the 25th because we’re just past midnight on the 25th when Neptune reaches its highest in the sky at local midnight. Our local midnight of course is at 01:00 thanks to our UTC +1 time zone, plus a little bit because we’re at the edge of our time zone. At about 1:24 Neptune is almost right in the due south. Stellarium helps, highlighting Neptune’s position when it isn’t really visible in the sky. While Neptune is at its peak we will take a closer look. Neptune is just next to a star at the moment, so there is a star nearby as we zoom in. We need to zoom in pretty close before we actually see Triton, Neptune’s largest, brightest and easiest to see moon. With Stellarium we can zoom in pretty close and take a look at Neptune’s rings and several of Neptune’s moons, but I do want to give a more realistic view, what you would see through telescope.

We’ll start using a pretty small telescope, a Celestron C8, so 8 inches aperture. We’re using a Plossa lens, 26 millimeters, which won’t help us too much, and we’ve got no Barlow lense. With that, Neptune and the star next to it are just about visible, we’re not seeing Triton at this level of magnification. We can zoom in a lot more, we can go up to much larger telescopes. We need to go through a few to get up to one of the larger apertures, the 16 inch aperture Meade LX200. That is the biggest Stellarium simulates and we’re still not seeing Triton, still just the star next to Neptune. We would need to use extra lenses to give us more magnification, for example a Barlow x3. This lets us just about catch Triton at the edge of Neptune. By using more powerful eyepieces, going down to a 6 millimeter Plossl, that increases our magnification. That makes Neptune and Triton clearly visible, but really nothing else is and it’s still quite fuzzy. We’re looking through a fair bit of atmosphere here because we are higher on the planet, we’re up nearer the north pole. Without any atmosphere we’re still really not getting much extra details. There’s atmosphere all over the planet Earth, but if you’re at the equator, you’ll be seeing Neptune practically at the zenith at midnight when it is at opposition, so you will be looking through less atmosphere in order to look at Neptune.

We’re going to go down to a binoculars, starting with a quite small binoculars, which of course isn’t going to show us very much. We’re going to go up to a much larger binoculars, the largest that Stellarium displays. this is the kind of binoculars that you would need a tripod to look through, they’re so big and heavy that it’s hard to hold them in your hands. That resolves Neptune and just about the star next to it, but with practically no details at all. That is the difficulty with Neptune. It is a very, very distant object, and the same way that the exact moment of the equinox happens at a given time UTC, the exact moment of Neptune’s opposition is the same. We’re getting it at just 7.68 magnitude, so really on the edge of visibility, just past visibility, really, even in a dark sky. We’re not seeing Neptune with the naked eye, certainly not with the Moon so close by. However, from other locations, Neptune may be a little bit closer to you, you may catch it closer to the actual moment of opposition, but with an object that’s so distant, we’re talking about a difference of, you know, maybe a few kilometers out of millions of kilometers, so it’s not a very big difference.

Looking at the Moon, it’s not quite full yet on the 25th, we need to move a couple of days ahead to the 27th. At just past midnight we’re at 99.8%. We’ll move back into the 26th, and we’re up to 100% just as the Moon is rising. The Moon is rising with a little bit of sunlight left in the sky, so this full Moon is going to look great. It’s often known as the Harvest Moon and this Full Moon is very likely to come up with that orangey golden color that we often associate with harvest Moons, even though it doesn’t always occur. By the time the sky gets darker and it’s later, the Moon will get back to that whitish gray that we’re familiar with. From here in Ireland, it will also go below 100%. For locations that are further east, the Moon rising in the east is 100%, if we moved ourselves further east, the Moon would get higher in the sky and, and we’d be seeing it at 100% closer to its peak in the sky. That is technically a better view of the Moon, but that is one of the things with these astronomical events.

Here in Ireland, we’re getting the equinox on the 23rd, we’re seeing the opposition of Neptune on the 25th, and we’re getting the Full Moon on the 26th. Only the Full Moon is actually 100% for us for sure, and it is only 100% as it’s rising, by the time it reaches its peak in the sky, we’ve gone past 100%, down to 99.8%. The equinox actually happens just after midnight, and we get it hours later, whether it’s the sunrise or the midday peak. The opposition of Neptune is just as complicated, perhaps even more so. Where the actual, absolute, perfect, 100% Full Moon peaks at midnight, where the maximum equinox occurs at midday, and the perfect location of Neptune’s opposition, they are going to be visible from certain locations on Earth. The broader event, the Moon at 99.8%, Neptune at almost opposition, the date of the equinox, those are going to happen for the entire world. I do hope you get to see them in real life and I hope that you enjoyed this piece. If you did, please do like it and if you like this kind of content, please subscribe to this website and my YouTube channel. Thank you very much for watching and hopefully I’ll see you back here next time.