Observing Mars during NAW

You can see Mars in the sky for yourself very easily in 2020, even from city skies. It’s due south in the evening, and you can read a full article about finding it here. But with the naked eye, and even through binoculars, Mars appears just as a slightly reddish bright dot of light. To see any details, you’ll need a telescope.

It doesn’t have to be a giant or expensive telescope, as long as it will magnify 100 times or more. This rules out most spotting scopes, as used for birdwatching, for example, but any telescope designed for astronomy, other than some starter models, should do the trick.

If you have such a telescope, but have never been able to get the hang of it, read this article which will solve most of the problems that people have. It is particularly important to get the finder of your telescope aligned properly, and to know which eyepiece to use when finding the planet. As soon as you are up and running, you should be able to see Mars clearly and make out its tiny red disc. 

Probably you won’t be able to make out any real details to start with. Even when close, Mars is still quite tiny. You need to magnify it about 100 times to make it appear large enough to see details on the planet.

With astronomical telescopes, you change magnification by using different eyepieces. It is the eyepiece with the lowest figure on it that gives the highest magnification.  Many telescopes are supplied with a Barlow lens, which has the effect of increasing (usually doubling) the magnification of any eyepiece they are used with. But the Barlows supplied with budget telescopes (which can include those costing well over £150) are often of very poor quality and you may find that you are better off without them, and just trying to make out the details on a less magnified image.

The other thing that can affect your view is what is called the ‘seeing’. This doesn’t mean how clear the sky is – in fact, often the reverse, as it refers to the steadiness of the atmosphere. Still, slightly hazy conditions often occur when the atmosphere is steady, while those sparklingly clear nights, with bright stars twinkling like mad, usually give planetary images that shimmer and jump around, as if viewed through a fast-moving stream.

You may even find that it’s hard to focus on Mars, and instead of a nice circular disc it is constantly in motion, maybe even splitting into two or three Mars images. Under these circumstances it’s usually better to give up for the night, and try again on another night.

What should you be able to see? 

With a good steady view of the planet, even with a small telescope of about 70 to 100 mm aperture, you should see the disc with sharp edges. Details may not be obvious to start with, but take your time and look for more subtle dark areas than the photographs show – these are processed to make the markings more visible. 

Here are simulated views of Mars as shown through different sizes of telescope. The size shown is the telescope’s aperture – that is, the diameter of its main lens or mirror. The magnification varies in each case.

Mars as seen through different telescope sizes

Because Mars turns on its axis in almost exactly the same time as Earth, each night we see very nearly the same side of Mars as at the same time the previous night. On one side of Mars the markings are fairly bland, with one half of the disc darker than the other half. On the other side, there is more variation in the markings. So you will get a slightly different view by waiting for a couple of hours, or observing earlier in a few nights’ time. 

People in different time zones from the UK will be observing different sides of the planet as well. So with a worldwide network of observers, all aspects of the planet are covered.

From the graphic below you can see how the view you will get changes over the course of a night, or over the course of National Astronomy Week. During the evening, the orientation of the planet also varies as it changes position in the sky. These views are shown with south at the top, as shown by most astronomical telescopes. If you are using a telescope with a star diagonal, bear in mind that you will get a mirror-image view as well.

How Mars rotates
How Mars rotates during NAW as seen from the UK. View shown for 250 mm telescope with south at the top

Other features

The tilt of Mars's axis means that it undergoes seasons just as Earth does, and also that the hemisphere that is pointed towards us changes from one close approach to the next. Currently the south polar cap is on the hemisphere facing the Sun, so it is quite small, although it never fully disappears. So with a small telescope it might be difficult to make out. You might see what appears to be a large white area, but this is more likely to be cloud on Mars. These are quite common, and can appear particularly on the morning side of Mars. Although the atmosphere of Mars is thin, it still has clouds of water ice crystals, just as we get on Earth.

From the images above you can see that the features are rotating from right to left in an inverted view, with south at the top, so the morning side is on the right. This side is also very slightly in shadow, as Mars is now past opposition and we are seeing it a little to one side, although we never see Mars showing strong phases like the Moon or Venus.

Another possibility is that you might see no dark markings at all, or some appear indistinct. This occurs from time to time particularly around the time of a close opposition, when solar heating of the surface is strongest and the dust is whipped up. On some occasions, the whole planet may be enveloped in a dust storm, as happened in 2018.

So don't be discouraged if your first close-up views of Mars don't show much. Keep at it, and you may be rewarded with your own sightings of our neighbour world.

Names on Mars

The various dark markings have fanciful Latin names, following the tradition of naming the features on the Moon. Here is a map showing the main features. Use it to identify the features shown in the views higher up this page.

Map of Mars made by Martin Lewis from observations carried out using an 8¾-inch telescope from St Albans, UK. South is at the top.

Last Updated: 2020-10-04 20:39:40