Take the chance in September to get outside and gaze at planets. Saturn and Neptune are in full opposition this month. That term may not be familiar to everyone, but this makes them much easier for the hobbyist astronomer to see.
When a planet is in opposition, it means that the Earth is directly between the sun and the planet, meaning the planet will remain visible in the night sky for the maximum amount of time that it can. When planets aren’t in opposition, part of their daily cycle occurs during daylight hours, limiting the amount of time you can see them at night.
The Seeliger Effect, also called the opposition effect, also comes into play here. Essentially, something will appear brighter when illuminated from behind the viewer. In this case, the sun is behind the Earth and is illuminating Saturn. The Seeliger Effect not only makes Saturn brighter but also brightens its iconic rings, making it easier to see them when viewed through a telescope.
Saturn will enter opposition on Sept. 7-8. Neptune is next on the evening of Sept. 20-21. On those dates, each planet will be in the sky all night from sunrise to sunset, giving astronomers plenty of time to find and view them. In the case of Saturn, it’ll also appear bigger and brighter than normal.
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When is the best time to look at Saturn and Neptune?
For Saturn, the evening of Sept. 7 and the morning of Sept. 8 will be your best bet. Saturn will rise at around 8:10 p.m. local time in the eastern sky and begin its trek across the sky. It’ll set at approximately 6:50 a.m. the following day, just before sunrise in the western sky. By Sept. 20, Saturn will rise around 7:20 p.m. local time and set around 6 a.m. local time on Sept. 21. While opposition is technically taking place on Sept. 7, you’ll have plenty of time throughout September to see Saturn for most of the night.
Neptune is much the same way. On the evening of Sept. 20, Neptune will rise out of the eastern sky at around 7:40 p.m. local time and set at around 7 a.m. the following day. Opposition is on that day, but as with Saturn, you’ll have a few weeks to observe it, as it’ll still be visible in the sky for most of the night.
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Will I need a telescope to see Saturn and Neptune?
If you want to see the cool stuff, yes, you’ll want a telescope or very high-powered binoculars. Technically, Saturn will be visible to the naked eye. It’ll look like a bright star in the sky. However, you can see Saturn for large portions of the year as a star in the sky, and if you plan on watching it this way during opposition, you’re seeing only half of the good stuff.
Thanks to the aforementioned Seeliger Effect, the rings of Saturn will be brighter and easier to see than they are during the rest of the year. A telescope will help skygazers catch a glimpse of its famous rings.
In the case of Neptune, you’ll definitely need a telescope or at least high-powered binoculars to see it. It’s simply too far away to spot with the naked eye without some sort of assistance. While it’s in opposition, you’ll have all night to find it.
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How do I find Saturn and Neptune?
The two planets won’t be too far apart from each other in the night sky. Saturn will spend most of the month hanging out with the Aquarius constellation. It rises in the eastern sky, flies overhead over the course of the evening and sets in the western sky just before sunrise.
Neptune will take a similar trek, rising from the eastern sky, going overhead as the night goes on, and setting in the west right before sunrise. It’ll be hanging out in the Pisces constellation, which is right next door to Aquarius. So you won’t need to look all over the sky to find both of them. Once you find one, the other isn’t too far away.
If you need help locating them, Stellarium and Time and Date have web-based tools that let you surf the night sky from your general location, which can help give you an idea of where to look. Star Walk 2 is available on iOS and Android if you prefer to use your phone to find them.
When will Saturn and Neptune be in opposition again?
For Neptune, the answer is easy. It’ll be in opposition again next year, approximately 48 hours later than it was this year. Neptune’s orbit takes 165 Earth years, so it moves only a little bit in the time it takes us to get around the sun. Thanks to this, Neptune goes into opposition once every 367 days on average. It’ll continue to happen in the autumn for the next few decades. Neptune will eventually be in opposition on Christmas Eve in the year 2066.
It’s not too different for Saturn, except it moves further along the calendar than Neptune does every year. In 2025, Saturn will be in opposition on Sept. 21 while 2026 will see it happen on Oct. 4. That means next year, Neptune and Saturn will be in opposition within two days of each other. After that, they’ll get farther and farther apart and won’t be in the same month again until 2060.
While you’re searching up at the sky, take a look to see if the T Coronae Borealis has popped yet, putting a new, temporary star in the sky. Also, if you’re up early, you should be able to see Mercury and Saturn in the sky without a telescope at the same time.
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