How to See Mars Through a Telescope

When it is nearby, seeing Mars through a telescope is a spectacular sight. When it is at its farthest, the view is much less inspiring.

Although it’s our neighbor in space, the distance between Mars and Earth fluctuates massively over a two year period. At their closest, they can be just 35,000,000 miles (56 million km) apart. When they are on opposite sides of their respective orbits, Mars can be 250,000,000 miles (401 million km) apart.

Valles Marineris on Mars
Mars showing Valles Marineris (click for full size)

You won’t be surprised to learn that the view you’ll get of Mars in your telescope when it’s 7x closer to us is spectacular compared to when it is at its most distant.

At its closest, the disc can be 25 arcseconds in diameter, at its furthest, it can be just 3.5″ across, smaller than Uranus in your telescope. This has a significant impact on the planet’s apparent magnitude too, which can be as dim as +2.0, or as bright as -3.0.

Suffice to say, you need to pick your moment to look at Mars. Sometimes it is a tiny, uninspiring red dot. At others, it is a large disc, rich in features to be discovered.

Read on to find out when you should be looking for the red planet, and what to look for when you’ve found it.

When Is Mars Visible?

2020 was a great year for seeing Mars. In October of last year, it came as close to Earth as it has for more than eight years. We saw the Martian disc reach 22 arcseconds wide, and it shone at magnitude -2.6.

Unfortunately, this means that 2021 is a fallow year for Mars. There is no opposition to be enjoyed and the planet spends the first half of the year getting smaller and fainter as it moves closer to the Sun.

This means its surface features and its moons, Phobos and Deimos, are practically impossible to see without a large telescope.

The story gets no better as 2021 progresses: Mars gets too close to the Sun to be seen from around July. It reaches conjunction on 08 October, when it will be directly behind the Sun from our perspective, and does not appear in dark skies again until the very last days of the year.

How to Find Mars In A Telescope

It might not be at its best this year, but the earlier you look, the larger and brighter the Martian disc will appear.

Here’s our guide to getting the best of Mars in 2021.

Step 1: Is Mars in the Sky Tonight?

As mentioned above, Mars is best viewed in the evenings in the first half of 2021, and the earlier in the year you look, the better it will appear.

The screengrab below from SkySafari 6 shows the path of Mars against the background stars this year. Remember, there is no Sun shown on this image and, in reality, Mars will be too close to our star to be viewed from late-July until late-December.

Click here to see our complete month-by-month guide to seeing Mars in 2021.

The path of Mars against background stars from Jan to July 2021
The path of Mars to July 2021 (click for full-screen)

When Mars re-emerges from behind the Sun in December 2021, we’ll find it in the constellation of Ophiuchus an hour before sunrise. Its disc will be tiny – about the same as that of Uranus – and it’ll be shining at magnitude 1.5.

Step 2: Finding Mars Without a Telescope

In the earliest weeks of the year, Mars is still relatively bright and easy to spot in the evening sky. As shown in the diagram above, you can find it in Pisces in January, then Aries, Taurus, and Gemini as the months progress.

In January see it best around 8pm. From March until we lose it July, Mars is best viewed as soon as it gets dark after sunset.

As the ‘Red Planet’ name for Mars suggests, what makes this planet easy to pick out against the stars is it shines with an obvious red hue. It will also be brighter than almost all of the stars nearby.

Step 3: Finding Mars With a Small Telescope

Make sure that your telescope is ready to go, i.e. you have aligned the finderscope. If you don’t have a telescope yet, these are our top picks for telescopes to see Mars.

Aim your finderscope at the red ‘star’ you picked out above and take a look through a wide field of view eyepiece.

While actual stars will remain as pinpricks of bright light, Mars will appear as a distinct disc, albeit a shrinking one as 2021 ages.

Mars is still relatively bright, so don’t be shy to use larger magnifications to see what you can observe on its surface. However, keep in mind that this year is not great for seeing details of the Martian surface.

Targets To Look For When Observing Mars With a Small Telescope

To prepare for observing Martian detail, it may well help you to have a number 56 bright green eyepiece filter, this will enhance surface contrast and show details you might otherwise miss.

When Mars is large and presenting good viewing, these are the features you should try to observe.

Target 1: How to See Polar Ice Caps on Mars

Even though Mars has almost no atmosphere, the top and bottom of the planet both experience the growth of polar ice caps during the respective northern and southern winters. We can see these using a small telescope, especially when Mars is closer.

The southern cap tends to be most obvious when Mars is at opposition (closest to us). Have the patience to wait for moments of good seeing and note the distinct white ice caps against the red of the planet.

Mars showing south polar ice cap
Hubble picture of Mars, showing south polar ice cap

Target 2: Martian Surface Features

The Martian surface has Valles Marineris, a valley deeper and longer than the Grand Canyon, and the tallest volcano in the solar system – Olympus Mons.

Discover more about Mars: What is Mars Made Of, And Why Is It Red?

A smaller backyard scope will not see these features directly, but we can see the different seas (mares) as darker areas in the landscape.

Use a Martian map, like this one, as your guide to see what you can discover. Begin by targeting large areas, like Mare Acidalium.

Target 3: Dust Storms

By their nature, Martian dust storms are unpredictable.

They tend to be massive and can be picked up in a telescope when the planet is nearby. Sometimes, on average every five years, the whole planet becomes enshrouded in sand.

Our advice is to keep up with discussions on Cloudy Nights’ solar system observing forum. This is where conversations about Martian dust storms will be had as soon as they happen.

Got a Larger Telescope? See Our Guide to Major Surface Features on Mars

Summary

Mars is iconic.

Its red body is a sight all astronomers want to see and explore with their telescopes.

Enigmatically, it only reveals itself fully to us for three or four months every two years. And, sadly, 2021 is not one of them.

However, it pays to be ready to observe Mars when it is back to its magnificent best, so practice seeing it now, even though it’s distant. This will be the perfect preparation for the thrill of seeing it up close, when it next reaches opposition in December 2022.