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4G: Saturn

In this section you will learn where to find the planet Saturn in the night sky over the coming months and the best things to look for when you see it.

Saturn

If any view through your telescope is guaranteed to make you want to see more, it’s your first sight of Saturn and it’s other-worldly rings.

For that reason, even though it is the furthest planet from us that this course covers, I would not be surprised to discover that it’s the first one you try and see with your telescope!

The picture below shows the beauty of the planet in October 2017. Sadly she doesn’t look quite this awesome through a backyard telescope, but she is beautiful nevertheless.

Saturn from SkySafari 5

Image Courtesy of SkySafari Pro – www.SkySafariAstronomy.com.

Finding Saturn is easy to do, if you look at the right time – see the calendar below – and even a small telescope will show off her rings. A larger telescope will even show you the biggest division between the rings, which you can see on the picture above between the whiter and grayer bands, called the Cassini division.

As Earth and Saturn move closer together and further apart over the course of our respective orbits, the apparent size of Saturn in the night sky moves between 14 arcminutes at its smallest, to 20 arcminutes at its biggest (excluding the rings). This sees its brightness fluctuate from magnitude +1.5 at its dimmest to -0.2 at its brightest.

Before we delve into what we can see when looking at Saturn, let’s first focus on when and where we can see it over the coming months.

Where to Find Saturn in the Night Sky

Remember, like all the planets, you will always find Saturn on or near the ecliptic, so refer back to the guide to the ecliptic section for information on where to find it. Saturn spends the whole of 2019 in Sagittarius.

Saturn becomes visible for observation in the second part of January and visually improves to opposition in July. Before opposition, Saturn is a morning object and afterwards it’s an evening object. The planet is visible all year except the first three week or so of January.

2019

January: The ringed planet begins the year too close to the sun for us to observe it and only comes back to some tricky dawn observing in the third week of the month.

At the end of the month it shines at magnitude +0.6 and has a disc of 15 arcseconds diameter. By the end of the month, seeing Saturn’s rings will be a much easier task as it rises 90 minutes before the sun. Although it is still low to the horizon, try and find it in the southeast sky.

February: Saturn rises at 5am mid-month and reaches 10° above the southeast horizon an hour before sunrise. See it skirt close to Venus on the 18th of the month. Shining at magnitude +0.6 and with a disc of 15″ the rings will make for a lovely sight even though seeing is not fantastic just yet.

March: As time moves on we get a longer opportunity to observe Saturn higher in the sky. It rises about 4:30am in the middle of the month and is 15° above the southeast horizon by 6am.

April: The ringed planet rises another hour earlier this month and although transit happens in daylight, we can see the +0.5 magnitude disc 25° over the south-southeast horizon at 5am. The disc is beginning to grow as opposition moves closer, this month it’s 17″ across.

May: As dawn breaks, Saturn is transiting some 30° over the southern horizon and shining at magnitude +0.4. The planet is now rising between midnight and 1am.

June: Rising at 10pm, Saturn reaches its highest point above the southern horizon at 3am. It’s grown again as we’ve moved closer to 18 arcseconds and, as a result, it continues to brighten. At the middle of June, Saturn shines at magnitude +0.2.

July: Opposition – the closest point to earth – is reached on the 9th of July. On that day, it will transit almost 30° above the southern horizon at 1:30am. At the same time it will be fractionally brighter at magnitude +0.1 but the disc will still appear 18 arcseconds across (compare that with Jupiter’s at 46″ on its closest approach to earth).

August: From here until the end of the year, Saturn is an evening object. In the middle of the month we can see the planet transit at the socially acceptable time of 11pm with almost exactly the same size and brightness of last month’s peak. Just make sure to look when the moon is not around to spoil the view.

September: Saturn sets around 1am but offers lovely viewing before then. At 10pm in the middle of the month, it’s 25° above the south-southwest horizon. Shining slightly dimmer now at +0.4 but the disc is not appreciably smaller at 17″.

October: This month is the last chance to see Saturn transit in some darkness, i.e. reach its highest point in the sky over the southern horizon. By month’s end, transit will be in daylight but the planet will not set until after 10pm.

November: Setting by 8:30pm this month, we have a much-limited observing window. At 7pm, the planet is just 15° above the southwest horizon, has shrunk to 15″ and dimmed to magnitude +0.6.

December: This will be the last chance to see Saturn for a while. At mid-month the ringed planet sets less than 2 hours after the sun and, by month’s – and year’s – end, Saturn will be lost in the glare of the sun.

What to Look for When Viewing Saturn

The first and most obvious attraction for an astronomer are Saturn’s rings. I’ll take a look at them first, but there are other sights to enjoy too, so keep reading to discover more.

Saturn’s Rings

The most simple observing act for astronomers looking at Saturn is to see her rings.

They are unmistakable and mark the planet out as the most unusual body in the solar system.

Saturn and Her Rings

Even the smallest scope required for this course will show you the clear space between the rings and the planet itself. What this looks like depends on when you are seeing it.

As Saturn and our own planet make their way around the sun, the amount of the rings’ surface we can see varies. Look on this page to for a pictorial example of what I mean. It shows how the rings changed their orientation towards us between 1996 and 2000.

The change in our viewing angle of Saturn’s rings varies over a fifteen year cycle.

At the end of 2017 we see the top of the rings as clearly as we ever can from Earth. This is because they are tilted at the maximum angle of 27° towards us.

Slowly that angle decreases and we see the rings more edge on. On 23rd March 2025 Saturn’s rings will be exactly edge on to us. When that happens, we will not be able to see them through a scope because they are so thin – as little as just a few hundred yards wide.

In fact, for most of 2024/25, there will be little to see of the rings at all. However, after 2025, we’ll be able to see the underside of the rings and the angle will increase towards its maximum tilt of 27° in 2033. After that, the whole process reverses again.

Don’t worry for now, even by the end of 2019 the rings are at an angle of 24°, so we have pretty spectacular views for a few years to come.

(If you have the inclination, this link will take you to a ‘Saturn’s rings ephemera calculator’. Enter any date you want into it, up to 2599, and see the tilt angle of the rings for that date.)

Divisions and Shadows in the Rings

I mentioned the Cassini Division at the top of this page. This is the famous black space or gap between the two biggest rings of Saturn, Ring A (furthest from the planet) and Ring B, see the picture below.

This is ‘seeable’ in the smallest telescope required for this course, under a dark sky and especially now, as the rings are so well placed. Don’t be afraid at to increase your magnification to glimpse the Cassini Division, which you do by moving to smaller eyepieces (e.g. a 9mm instead of a 12mm).

Averted vision will increase your chance of seeing the division, but nothing makes more of a difference than a dark sky and steady seeing. There are many great opportunities for the seeing detail in Saturn over the coming months, patience and persistence (as always with astronomy) are your friends.

The Encke Division is an even smaller gap in the rings, as shown below between rings B and C. This is a hard challenge even for those with 8″ apertures or bigger, so is outside the scope of this course, but certainly worth a try if you can get access to a bigger scope, like from your local astronomy club.

Rings A, B and C, and the Divisions Between Them

Ring Shadows

You can also try to see shadows cast by the planet on the rings, or those cast by the rings on the planet, depending on where the sun is.

At the right time of year – when Saturn is in the south or west at sunset (see the calendar, above, for details) you can see the shadow of the planet falling across the rings. To spot the shadows, use averted vision and don’t stare directly at the planet in your eyepiece. What other details do you notice in your peripheral vision? Do you see any colors?

If you are not yet at the limit of your telescope’s magnification, try one more step up by using your next smallest eyepiece, or a combine a Barlow Lens with your largest eyepiece. Does that reveal more to you, or is it a step too far and you had more enjoyment with lower magnification?

Experimentation and persistence will pay off.

Titan, and the Other Moons of Saturn

There’s a good reason for singling out Titan in the title of this section: it is the biggest of Saturn’s moons by quite some margin. Not only is it bigger than our own moon, but it’s also larger than Mercury and Pluto!

At over 5,000km across, it is more than 3x the size of the next largest moons of Saturn, which are called Rhea and Iapetus.

Because it’s larger, it is also brighter and the easiest target for your telescope.

Titan shines between magnitudes 8.2 and 9.0. Your eyes, at best under dark skies, can see to magnitude 6, so Saturn itself is bright. However, Titan is beyond the reach of our eyes alone and needs your telescope to reveal it.

You’ll be pleased to learn that Titan is easy to see. It is the orange/brown ‘star’ near to the planet itself. It orbits the planet every 15 days and, depending on when you look, can be found a good way out from Saturn itself.

I use SkySafari to find out where Titan is at any given time (see video below), but you can use this free resource from Sky & Telescope Magazine to do the same thing.

Video Courtesy of SkySafari Pro – www.SkySafariAstronomy.com.

It is possible to see Rhea and other large moons of Saturn through a small telescope, but they are more of a challenge. Please read this detailed article I wrote on Love the Night Sky for more detailed information.

Saturn’s Surface Features

The final thing you should try to observe on Saturn is her faint surface bands.

They are much less pronounced than Jupiter’s but they can be seen with careful observation under a dark sky. However, even when all conditions are excellent (i.e. rarely) you shouldn’t be disheartened if you find it impossible to see them. This challenge is right at the limit of what’s possible for a small telescope.

You will need to push your scope up to 200x magnification, which requires good seeing, at least a 4″ aperture and dark skies.

If you want to give this a go, plan your attempt when Saturn is as close to the zenith as possible. Use the calendar above to see when this happens in the coming months. You have an even better chance of seeing Saturn’s bands if you look when it is closest to us, which happens every 54 weeks at its opposition. Opposition dates for the next few years are as follows:

2019 July 09

2020 July 20

Don’t be too concerned about missing the exact date as Saturn stays relatively close to us for many weeks either side of them.

If you are able to push your telescope towards 200x magnification, you will see different colored (gray) bands on the planet’s surface. They may not be distinct, and it will be practically impossible to identify individual bands, but you will know you’ve already progressed a long way in your seeing skills if you can see any gradients in the shading of Saturn’s surface.

Summary

Saturn, for me, is the most enchanting of all the planets because of her floating rings. The rings themselves present a great seeing challenge and spotting Titan is a must for anyone spending time with Saturn in their eyepiece.

Saturn brings this course’s planet guides to a close.

It’s time now to leave the solar system behind and move on to your biggest challenge so far: Deep Space Objects.