When it is nearby, seeing Mars through a telescope is a spectacular sight. When it is at it farthest, the view is much less inspiring.
Although it’s our neighbour 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.
You won’t be surprised to learn that the image of Mars 7x closer to us is spectacular compared to when it is at its most distant.
At is 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 in 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?
2019 is a not a great year for seeing Mars. Although it is visible for a lot of the year, it’s a long distance from us and does not present good viewing. To get more detail, check out our guide to when the planets are visible.
In 2020 the story improves. Mars and Earth slowly move closer together such that, by August, the red planet will be shining at magnitude -1.1 and 14″ wide in your telescope.
Mars’ next closest approach happens on 06th October 2020, when the planet will be less than 39 million miles (63 million km) from us.
On that date, the planet will shine at magnitude -2.2 and will present a disc almost 23 arcseconds across. As you can see in the Sky Safari screen grab below, we’ll find Mars in Pisces.
How to Find Mars In A Telescope
Step 1: Is Mars in the Sky Tonight?
There’s no denying that Mars is much better to view in 2020, but it is visible in 2019. Before you can view it, you need to know if it’s visible.
The picture below, which is a Sky Safari screenshot, shows its path across the sky this year. You can see that it will travel from Gemini in early summer, through Cancer, Leo, Virgo and ending the year in Libra.
In reality, it spends summer too close to the sun for us to see it. However, by October, Mars reappears in the morning sky, rising an hour before the sun in the middle of the month.
The position improves from then onwards, as the red planet rises earlier and earlier as the year draws to a close.
Step 2: Finding Mars Without a Telescope
Even when it is visible, the Martian disc is a dim magnitude +1.6 and a teeny, tiny 4 arcseconds across. This will make it a tough spot.
In November, look east in Virgo an hour before sunrise and, in December, look 20° above the southeast horizon an hour before sunrise.
The brighter red-looking star you see in Libra will be Mars. The best way to confirm you have the planet in your sights is to train your telescope on it.
Step 3: Finding Mars With a Small Telescope
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 dics, albeit a very small one.
Mars is still relatively bright, so don’t be shy to use larger magnifications to see what you can observe on its 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
The top and bottom of the planet both experience 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 patience to wait for moments of good seeing and note the distinct white ice caps against the red of the planet.
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.
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, 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.
Mars is iconic.
Its red body is a sight all astronomers want to see and explore with their telescopes.
Enigmatically, it only reveals itself to us fullf for three or four months every two years.
Because of that, it pays to be ready to observe Mars, so practice seeing it now, even though it’s distant, so you can experience the thrill of seeing it up close in October 2010.