Mars, often referred to as the “Red Planet”, stands out in the Solar System with its distinctive red-orange hue. This unique color is the result of iron oxide, commonly known as rust, present in its surface sands and dust. When sunlight reaches Mars, it illuminates the dust particles suspended in the Martian atmosphere, further amplifying the reddish hue. This reddish dust not only colors the planet itself but also gives the sky on Mars’ surface a tawny, pinkish color, particularly at sunrise and sunset.
The naming of Mars has a rich history steeped in mythology. Astronomers named Mars after the Roman god of war due to its blood-like, red appearance. This association with war and aggression made it a fitting symbol for the Roman god Mars, known for his military might and prowess. However, this wasn’t just a Roman idea. The ancient Greeks also associated the planet with conflict, calling it Ares after their own god of war.
Mars is certainly one of the more interesting planets to view through a telescope. Being the only planet in the solar system with actual surface features you can see (Mercury is tiny and rarely easily viewed, and Venus has its obscuring clouds), as well as hosting dust storms and two moons, there is certainly a lot to look at. The allure of Mars, its Earth-like status, and the possibility of hosting life have also attracted stargazers for centuries.
First, let’s go over some of the important things you need to view Mars with your telescope.
Observing Mars Through A Telescope: Viewing Prerequisites
1: Wait for Opposition
Mars only makes a close approach to Earth once every 26 months, and it is at its closest to us approximately around when it appears 180 degrees from the Sun in the sky, known as opposition. For a few months on either side of that date, it is big enough in the sky to easily view surface features. For the rest of the time, Mars appears rather small with a telescope, and it is far more difficult to discern any surface features. Mars and its moons also appear much brighter at opposition. The next opposition will occur in January 2025, with subsequent ones in early 2027 and 2029. Unfortunately, Mars is getting closer to aphelion, and the next “good” (i.e., close to perihelic) opposition won’t be until the late 2030s.
2: Good Atmospheric Seeing
Atmospheric turbulence, or “seeing”, causes Mars and other small sky objects like the planets to appear shimmery or fuzzy in a telescope. This can be caused by a number of factors, including:
- Looking over a surface that soaks up the heat in the daytime and releases it at night, such as pavement, concrete, or roofs
- Being located under the jet stream
- Natural atmospheric disturbances
- Ideally, you should be looking over grass, water, rocks, or sand, not rooftops, chimneys, asphalt, or concrete. Observing near the ocean or over another body of water—if you can avoid sand and salt damage to your telescope—is optimal, as is observing from a hill or mountain top.
The lower Mars or any object is in the sky, the more atmospheric seeing will affect it. For best results, try to observe Mars on a telescope when it is at its highest in the sky.
3. Aperture
The larger your telescope, the more angular resolution it has and the fewer details you can see. Unlike light gathering ability, which scales with the square of the aperture, resolution is linear, so an 8” telescope will have twice the resolution of a 4” telescope.
However, once you get past about 10” or 12” or so, it is rare that you will ever have a night of seeing good enough to utilize the full resolution enabled by your telescope’s aperture, and thus it probably makes more sense to prioritize optical quality over aperture if you are able to afford a large telescope.
In general, assuming good seeing, I recommend using around 30-40x magnification per inch of the aperture when viewing Mars through your telescope. Most of the Martian features are relatively low-contrast and bringing up the magnification too much only smears them and makes them less defined. At the same time, too-low magnification will result in Mars appearing so bright that it’s hard to see anything.
4. Good Optics
A telescope with poor optical quality or defects can make a huge difference in being able to view significant detail on Mars. Anything short of optimal will result in light scatter, smearing of the image, or a complete inability to focus at high power. Thankfully, unless you have bought a really low-quality telescope, this is usually not a problem. A fast achromatic refractor telescope will show severe chromatic aberration, blurring fine detail, and is thus not recommended for viewing Mars.
5: Telescope Collimation & Cooldown
Any good telescope can be exciting for viewing Mars, even with just a few inches of aperture. However, good optics, good collimation, and good conditions are paramount. A good telescope is of no use if the collimation is bad or it hasn’t cooled down.
If you own a Newtonian or Schmidt-Cassegrain, you should check your collimation before every observing session and make sure it is as perfect as you can get it before viewing Mars. If you’re unsure how to collimate or check collimation, read our guide. With refractors and Maksutov-Cassegrains, you shouldn’t have to worry much about collimation. Cooldown affects all telescopes, though refractors suffer from the fewest cooldown issues. Even if the air temperature is only a few degrees lower than indoors, your scope’s objective lens or mirror will warp as a result of the temperature change and suffer from blurry images.
Newtonians can suffer from another thermal issue known as tube currents, where warm air hugs the tube walls for hours on end and distorts light before and after it hits your primary mirror. Tube currents are worsened by having a small tube only slightly larger than the mirror, particularly if it is made of metal, both of which are common on mass-produced Newtonians.
Typically, you should give your scope at least half an hour to cool down before attempting high-power viewing and use cooling fans if possible, particularly on Newtonians. Some Newtonians, such as the Zhumell Z series Dobsonians, come with cooling fans, and some vendors sell them to easily attach to your telescope. You can also make your own using 12-volt DC-powered computer fans and a battery pack, with minimal electronics knowledge or soldering required. Propping an ordinary house fan behind your primary mirror will also work in a pinch. Just remember to turn the fan off before actually doing any viewing!
6. Good Eyepieces
Low-quality eyepieces and Barlow lenses may cause scatter, chromatic aberration, and other defects that can make it hard to view fine details on Mars and more easily hide its moons within the planet’s glare. So try to get yourself some decent eyepieces. They don’t necessarily need to be wide-field, just free of scattering and chromatic aberration.
What Does Mars Look Like Through a Telescope?
Mars, like Venus and Mercury, goes through phases when viewed from Earth. These phases are due to the relative positions of Mars, Earth, and the Sun. When Mars is on the opposite side of Earth from the Sun (at opposition), it appears fully illuminated – this is its “full” phase. As Mars moves away from opposition and closer to conjunction (when Mars is on the same side of the Earth as the Sun), it passes through a gibbous phase (more than half illuminated but not fully illuminated) and then a crescent phase (less than half illuminated). However, Mars’ phases are less dramatic than those of Venus and Mercury because Mars orbits outside Earth’s orbit, so we never see it as a thin crescent.
Besides an occasional slight phase, Mars displays three main types of features through an amateur telescope: Albedo markings, polar caps, and dust storms.
Albedo features on Mars are lighter or darker regions that reflect different amounts of sunlight, due to the varying composition and texture of the Martian surface. These albedo features have been used for centuries to map the planet, even before the age of spacecraft. Large albedo features are visible even through small telescopes, and many have names, often based on the original names given by early observers. Some of the most prominent include Syrtis Major Planum, a dark feature thought to be a relatively low dust region, and Hellas Planitia, which is a large impact basin that often appears bright due to frost or fog. These albedo features, however, are not static – they change over time due to wind-blown dust covering and uncovering the underlying surface. These variations have intrigued Mars observers and added a dynamic aspect to the study of the planet.
Many astronomers in the past thought they saw “canals” on Mars. However, these linear features were usually caused by issues with the telescope – namely internal reflections; these observers would use ludicrous magnification with small apertures to the point that they would end up looking at reflections of magnified blood vessels in their eyes or spurious aberrations from the Earth’s atmosphere and confuse it for detail. There are no canals on Mars, and there never were any.
Some of the Martian albedo features do in fact correspond to topographical features, such as the Aurorae Sinus region, which is, in fact, part of the massive canyon Valles Marineris, Nix Olympica, which corresponds to Olympus Mons, the largest volcano in the solar system -, and, of course, Hellas Planitia, a giant ancient crater. However, most of the larger and thus more easily observed albedo regions are just patches of dark terrain.
Mars’ polar caps are pretty self-explanatory – frozen deposits of water and carbon dioxide ice at the poles. Because Mars has an axial tilt very much like Earth, you will usually only easily see one at any one time, with the other at least partially if not fully shrouded in darkness on the non-observable side of Mars. The polar caps are undoubtedly the easiest Martian feature to observe with a telescope, and almost any telescope will show them with at least 50x magnification or so around the opposition.
Lastly, there are dust storms. Martian dust storms can vary widely, from small orange-yellow patches to global storms that all-but-obscure even the most prominent albedo features and the ice caps. They usually happen during Mars’ northern hemispheric summer, which also corresponds to when Mars is closest to the Sun, thanks to its rather elliptical orbit. The extra heat stimulates Mars’ wind, and the low gravity and atmospheric pressure easily result in planet-wide dust coverage.
Conjunctions & Occultations of Mars
In astronomy, a conjunction occurs when two astronomical objects have the same right ascension or the same ecliptic longitude, usually as observed from Earth. When it comes to Mars, a conjunction happens when it aligns with another planet or the Sun as seen from Earth. The most notable of these is perhaps the Mars-Sun superior conjunction, which happens approximately once every 26 months. During this period, Mars is nearly opposite the Sun in our sky, making it difficult to observe because it rises and sets with the Sun. Conversely, an opposition (the opposite of a conjunction) is a prime time to observe and study Mars, as the planet is fully illuminated by the Sun and is visible throughout the night. Conjunctions between Mars and other planets are less regular but can provide a beautiful spectacle for stargazers, with two or more planets appearing close together in the sky.
For instance, on January 27, 2024, Mars will form a fairly close conjunction with Mercury, albeit very low in the pre-dawn sky, offering a rare spectacle for observers. This event will be followed by another conjunction on the morning of February 22nd, when Venus and Mars appear about ¾ to 1 degree apart – or a bit further than the diameter of the Moon or Sun in the sky – easily visible in the same view at medium power in a telescope or with handheld binoculars.
The next conjunction between Mars and another planet is on April 28, 2024, when Neptune and Mars will appear close to each other in the night sky. However, the most exciting conjunction of the year will occur on August 14, 2024. Mars and Jupiter will appear as close together as 18 arc minutes, which is slightly less than the diameter of the full Moon in the sky. Both planets will be visible after midnight, rising a few hours before the Sun.
Occultations occur when one celestial body passes in front of another, hiding the latter from view. Occasionally, the Moon occults Mars as seen from Earth, which happens at least once or twice in most years. However, most viewers will just see a close conjunction between the Moon and Mars, – still spectacular.
Observing the Moons of Mars with a Telescope
Both Phobos and Deimos are rather dim and really require at least an 8” telescope to see. Phobos orbits extremely close to Mars—so close, in fact, that it is only really observable when Mars is very close to opposition. Most of the time, it is too close to Mars in the sky and appears too dim to spot. Even with Mars favorably positioned, you’ll need to wait for Phobos to be at an optimal elongation from the planet, which, thankfully, occurs at least twice a night thanks to Phobos’ 7 hour, 40-minute orbital period. Even then, you’ll need to put a strip of tape or a similar occulting bar-like device across the center of your eyepiece’s field lens to block out Mars itself to shield Phobos from its glare at least partially.
Deimos is much easier. An 8” or larger scope with a good eyepiece can reveal the tiny asteroid, and observers with telescopes as small as 6” in aperture have spotted it. As with Phobos, an occulting bar is ideal for attempting to spot Deimos, and you must do it within a month or so around opposition, when the moons appear brightest and most distant from Mars.
Telescope Color Filters for Observing Mars
Some observers recommend using various telescope filters to bring up the contrast, or a neutral-density filter to bring down Mars’ brightness. Most are largely useless, either due to poor optical quality or a negligible contrast boost. However, we highly recommend the Baader Neodymium Moon and Skyglow filter for observing Mars from a telescope. It tones down some glare and any residual chromatic aberration from your eyepiece and enhances the vivid red and orange tones of the planet. A #21 orange filter is also used by some observers, though make sure to get a good one from a known brand so it doesn’t mess up the view.
Mars Facts
Mars has a mass of about 6.39 x 1023 kilograms, which is only around 10.7% of Earth’s mass. Despite its smaller size and mass, Mars has a similar land area to Earth when we consider that Earth’s surface is 70% covered by water.
Mars is a terrestrial planet, which means its composition is primarily silicate minerals and metals. Its surface is rich in iron, which gives the planet its distinctive reddish color due to iron oxide, or rust. The Martian crust is primarily composed of basalt, similar to Venus, and beneath the crust lie a mantle and a core. The core is not powering an active magnetic dynamo like Earth’s, and thus Mars lacks a protective magnetic field.
Mars is known to have the tallest volcano (Olympus Mons) and the deepest, longest canyon in the Solar System (Valles Marineris). These features suggest that there were active plate tectonics on Mars in the past, but it seems that Mars is a geologically inactive world now.
Mars is the second smallest planet in our solar system, with a diameter of approximately 6,779 kilometers. This is roughly half the size of the Earth. Mars is less dense than Earth, which means that despite its size, it has only about 38% of Earth’s gravity. Specifically, the acceleration due to gravity on the surface of Mars is about 3.71 m/s². You could jump nearly three times as high on Mars as you could on Earth.
Mars orbits the sun at a greater distance than Earth, taking about 687 Earth days, or nearly 1.88 Earth years, to complete one Martian year. This prolonged orbital period contributes to the planet’s seasonal changes, which are twice as long as those on Earth. However, the eccentricity of Mars’ orbit leads to significant temperature variations, making Martian seasons considerably more complex than Earth’s. Mars is the second smallest planet in the solar system, with Mercury being the smallest. Despite being over half the diameter of Earth, Mars’ surface area is equivalent to the combined dry land area of Earth, making it an intriguing focus for scientists interested in extraterrestrial geological formations and the potential for past life.
Mars follows an elliptical path as it orbits the Sun, which means its distance from the Sun can vary dramatically. As a result, Mars experiences seasons much like those on Earth, although they are nearly twice as long due to the planet’s longer orbital period. However, the eccentricity of Mars’ orbit contributes to significant differences in the length of Martian seasons. When Mars is closest to the Sun (perihelion), the southern hemisphere experiences summer, which is notably warmer but shorter than the northern hemisphere’s summer that occurs when Mars is farthest from the Sun (aphelion).
This elliptical orbit also has implications for Mars’ distance from Earth and the quality of observing opportunities, particularly during oppositions when Mars and the Sun are on directly opposite sides of Earth. When Mars reaches opposition near its perihelion, the event is known as a “perihelic opposition,” offering observers the best view of the Red Planet. The last such event happened in 2018, and the next will be in 2035. In contrast, when Mars reaches opposition near aphelion, the event is known as an “aphelic opposition,” during which Mars appears smaller and less bright. This variability in viewing conditions underscores the importance of taking full advantage of favorable oppositions.
The surface temperature of Mars varies significantly due to its elliptical orbit and thin atmosphere. It can be as cold as -87 degrees Celsius in the winter at the poles, while during the summer and at the equator, the temperature can reach up to -5 degrees Celsius. These extreme temperatures make the Martian environment harsh and challenging for potential human exploration.
Like Earth, Mars also rotates on its axis, completing one rotation every 24.6 Earth hours. This period is often referred to as a “sol” to distinguish it from an Earth day. Mars’ similar day length results in a comparable pattern of day and night to Earth’s. However, due to the difference in orbital speeds, it takes about three weeks for observers on Earth to view the entire Martian surface as the planet rotates.
