The Ultimate Guide to Observing Mars

Beyond Earth’s orbit lies the fourth planet from the Sun, Mars—a small, mysterious planet that has intrigued mankind for millennia. With its eerie, fiery reddish appearance in the night sky, Mars often looks as if it is preparing for battle, so it was fittingly named for the Roman god of war.

Unlike Venus and the outer planets, which are covered in clouds, Mars shows surface detail when viewed through a telescope. Nineteenth century astronomers noticed its surface was marked with crisscrossed lines resembling irrigation “canals” and ever-changing seasonal polar ice caps. This caused many to speculate that there could be intelligent life on the planet.

Mars has captured the imaginations of scientists and creative thinkers up and down the centuries. Perhaps the most infamous example was Orson Welles’ 1938 Halloween Eve radio adaptation of H.G. Wells’ novel, War of the Worlds. This dramatic broadcast made headlines and convinced many listeners that Earth was being invaded by Martians!

Since then, numerous space probes and landers have successfully journeyed to the Red Planet, beginning in the mid-1960s. Scientists now have a better understanding of this dry, desolate world filled with extinct volcanoes, canyons, craters, and a thin atmosphere.

While there are no “little green men” on Mars, humanity’s missions there have searched for signs of ancient microbial life. So far, none have been found, but with three spacecraft now en route and soon to be arriving to the Red Planet, including China’s Tianwen-1 Mars Mission, United Arab Emirates’ Hope Mars Mission, and NASA’s Mars 2020 Mission with the Perseverance Rover and the Ingenuity Helicopter, we may be on the brink of some exciting new discoveries in 2021!

For the amateur astronomer, observing Mars through a telescope can be just as exciting as collecting data from the rovers is for professionals. Best of all, you can do it right from your backyard! This guide will help you understand Mars and why it is such a favorable target. We’ll also provide equipment recommendations, methods of capturing your own Mars images, surface features to look out for, observing tips, and more.

Tip #1: Understanding Mars Opposition

Earth and Mars both travel around the Sun in oval-shaped or elliptical orbits; neither planet’s orbit is a perfect circle. As a result, the distance between the two planets varies greatly. Mars Opposition occurs when the Earth catches up to Mars in their respective orbits and is placed in between the Sun and Mars. The Sun and Mars appear on opposite sides of the Earth. So, from our viewpoint, Mars rises in the east as the Sun sets in the west and remains visible all night long. Mars Opposition occurs about every 26 months.

Very close Mars Oppositions occur every 15 to 17 years, when Earth passes between Mars and the Sun around the time of Mars’ perihelion (closest point to the Sun) in orbit. In 2003, Earth and Mars met near their narrowest points in their respective orbits and provided a once-in-a-lifetime viewing experience. At that time, the distance between Earth and Mars was less than 35 million miles—the closest they have been to one another in 60,000 years! Mars grew to an impressive 25” in apparent diameter and was at its brightest magnitude, -2.8! For comparison, during a non-favorable opposition year, Mars can be as far as 62 million miles from Earth.

It is important to note that the date of Mars Opposition and the date of Mars Closest Approach do not fall at the same time and can vary by several days. Due to orbital mechanics, the date of closest approach can take place a few days earlier than opposition when Mars is moving away from the Earth and Sun. When Mars moves towards the Earth and Sun, closest approach can take place a few days after opposition.

The last Mars Opposition took place on October 13, 2020. Since then, Mars’ orbit will continue to recede away from Earth’s orbit as they circle the Sun. Its next scheduled opposition will occur on December 8, 2022. Mars’ size will appear smaller during future oppositions through 2027 before its orbit begins to close in on Earth’s once again for the next cycle.

Tip #2: Use an astronomy app or star chart

How can you find Mars? Well, if you been following Mars since last year’s opposition, you will probably know Mars is still visible in the night sky and is currently between the constellations Aries and Pisces. But for the rest of us, star charts in astronomy-related magazines or websites are helpful visual guides to spot Mars.

The most modern and informative tools today can be found in astronomy apps such as Celestron’s SkyPortal mobile app. This full featured planetarium app is included with the purchase of any Celestron telescope, available from the Apple App Store or Google Play. SkyPortal instantly provides new telescope owners with a wealth of information at their fingertips, including audio and written descriptions about Mars. It also provides its celestial coordinates, a real-time sky map, rise and set times, physical and orbital parameters.

Tip #3: The best equipment for viewing Mars

Telescopes: Any small telescope with an aperture of 60mm to 90mm will be able to reveal some surface markings on Mars about a month or so before, during, and after an opposition, although the image scale will be small and the resolution somewhat limited. Telescopes such as Schmidt-Cassegrain and Maksutov-Cassegrain telescopes (seven inches and up), are our best picks for planetary observing due to their increased light gathering ability, longer focal lengths, and ability to accommodate higher magnifications (150x or more) on a night with steady seeing.

Resolution is a function of aperture, so consider using a larger telescope to observe prominent features on the Martian surface. The larger the telescope’s mirror or lens, the more light it will collect, but the heavier the telescope will be. You should carefully consider how much weight you can comfortably handle and your budget.

Color filters are a great way to enhance subtle features on the Martian surface and in its atmosphere for a more enjoyable observing experience. Filters can individually thread onto the end of eyepiece barrels or be stacked together to enjoy the benefits multiple filters at once. (Please note that when you stack filters, light is diminished. Doing so is only advisable with telescopes with at least 8” of aperture.) Here are the most popular color filters for enhancing details on Mars:

  • #80A Blue Filter - Enhances atmospheric clouds.
  • #58 Green Filter - Excellent for increased contrast of Martian polar caps, low clouds and yellowish dust storms.
  • #56 Light Green Filter - Increases contrast of Martian polar caps, low clouds and yellowish dust storms.
  • #25 Red Filter - Ideal for observing the polar ice caps and features on the Martian surface. Sharpens the boundaries of yellow dust clouds.
  • #21 Orange Filter - Reduces light from the blue and green areas that darken the maria, oases and canal markings, while lightening the orange-hued desert regions. It also sharpens the boundaries of yellow dust clouds.
  • #12 Yellow Filter - Reduces light from the blue and green areas that darken the maria, oases and canal markings, while lightening the orange-hued desert regions. It also sharpens the boundaries of yellow dust clouds.
  • #21 Orange - Increases contrast between light and dark features and penetrates hazes and most clouds.

Color filters are available in the following Celestron products:

A Variable Polarizing Filter - 1.25” #94107 can be adjusted to reduce light transmission and is beneficial for reducing glare.

Cameras and Phone Adapters: Smartphones’ built-in cameras are getting better and better. You can hold your phone up directly to the telescope’s eyepiece to take advantage of the telescope’s image scale with higher magnification to capture plentiful detail, but only when Mars is in a favorable position. You have the option of using the smartphone’s digital zoom feature to increase the size of the planet to your liking.  It can be tricky to properly center your target, but by using a smartphone adapter like the Basic Phone Adapter #81035 or the NexYZ 3-Axis Universal Smartphone Adapter #81055, centering Mars will be quick and easy.

DSLR cameras are another popular tool you can use to capture Mars. You will need a T-Adapter (there are different models available for your telescope), and a camera-specific T-Ring (i.e., Canon, Nikon, etc.). The T-Ring attaches to your camera’s bayonet, and the T-Adapter threads onto the T-Ring. Depending on the T-Adapter you are using, it will either slide into the eyepiece drawtube, or screw directly onto the telescope’s rear cell.

Planetary imaging cameras are also a great way to capture high-resolution images with tremendous detail. The camera takes the place of your telescope’s eyepiece and connects through a USB cable to your computer or laptop. Software analyzes each frame of the live video capture and throws away the images that are blurry due to poor atmospheric turbulence. It then stacks and perfectly aligns the clearest video frames to create a bright, detailed, colorful image.  Celestron’s planetary imaging cameras include:

Tip #4: What to look for while observing Mars

Mars often reveals subtle changes from opposition to opposition, but every so often, a significant change does occur. In 2018, there was a massive Martian dust storm that engulfed the planet and limited the amount of detail that was visible. This time, the surface is much clearer. For the best views, you will need a larger aperture telescope and a lot of patience to find just the right time when the air settles and details pop into view. So, what prominent Martian features should we look for in the couple of months leading up and after an opposition?

Phases: Although Mars does not exhibit the full range of phases as seen from Earth, it does appear almost always in a gibbous phase, leading up to a full phase at opposition.

Polar Ice Caps
: Like the polar ice caps on Earth, Mars also has ice caps at its poles that grow or wane with the season. They are much smaller and thinner than the Earth’s ice caps and made from frozen carbon dioxide (dry ice) as well as water ice, which lies beneath.

Land Formations:  Unusual dark surface formations on the Martian surface were named after seas or lakes. These maria appeared to change shape over time, but it was later learned these markings did not actually change but were periodically covered in dust and sand. Look for these large ancient volcanic “seas” such as Syrtis Major, Mare Tyrrhenum, and Mare Cimmerium. There are also smooth areas that were once thought of as continents. Look for Hellas Planitia impact basin, and Arabia Terra. Both appear to be covered in Martian dust. Olympus Mons, the largest volcano in the Solar System and roughly the size of Arizona, is 374 miles in diameter and 11 miles high. Although you are unlikely to be able to see it in a telescope, you might be able to spot the high-altitude clouds covering its location named Nix Olympica. One of the largest canyons in the solar system is Valles Marineris. It is so large that it dwarfs our own Grand Canyon! This Martian canyon is one of the largest canyons in the Solar System and can be seen through a telescope as a dark scar across the planet’s surface.

Dust Storms:
Martian global dust storms are unpredictable, but they appear to occur about twice every decade. The 2018 Martian dust storm prior to the opposition that year quickly engulfed the entire planet and limited the surface views from ground. This year appears to be free from any major dust storms, but they will likely return someday.

Observing Challenge #1: Although they are very tiny, you may be able to spot the two orbiting moons of Mars, Phobos and Deimos, if you’re up for a good observing challenge. While their close proximity to the overwhelmingly bright planet may make them a challenge to pick out from the glare, it can be done. You will need access to a large telescope 11” in aperture or greater, excellent viewing conditions, a lot of patience, and a lot of luck.

Observing Challenge #2: As Mars continues to grow smaller by the day through most of 2021, observe early as it will become harder to make out any surface detail. Let’s see just how far away Mars needs to be before we lose sight of any surface detail. Now who’s up for the observing challenge?

Tip #5: Helpful Observing Hints

Mars Visibility:  Although Mars does not reach opposition in 2021, it will still be visible for most of the year before eventually becoming like an inconspicuous second magnitude star before being lost in the Sun’s glare around late August. Mars will reappear again low in the east-southeastern morning sky from about November 24 and be visible through the end of the calendar year and into 2022. Other notable observing highlights: Mars will be close to a thin waxing crescent moon in the west-northwestern sky on the evening of May 15, 2021. On the evening of July 13, 2021, Mars will be in conjunction with a much brighter Venus, and on the evening of July 30, 2021, Mars will be seen just above the bright star Regulus in the constellation Leo, so mark your calendars!

Steady seeing conditions are critical when observing Mars: Avoid nights of bad seeing when the atmosphere is turbulent when Mars appears like a boiling reddish blob in the telescope. Start with low magnification and work your way up if the views remain steady. During the Mars Opposition of 2003, some of the clearest and most detailed views of Mars took place in the early morning hours while the atmosphere was calm and steady.

Cool your telescope down: Make sure you bring your telescope outside about an hour or so before you plan to observe to cool it to ambient temperature. It is important for the telescope to reach thermal equilibrium with the outside air temperature to avoid distorted views. Telescopes with large mirrors and lenses may take longer to properly cool down for the best views.

Collimate, collimate, collimate: If you own a Newtonian or Schmidt-Cassegrain telescope, make sure your telescope’s optics are collimated. It can make a difference when it comes to discerning fine planetary detail. If the optics are slightly out of alignment, you may be cheating yourself out of seeing the best and sharpest views. Make it a habit to check collimation and adjust as needed once your telescope is cooled down. Most refractor telescopes generally cannot be collimated.

Observe often: Mars rotates on its axis once every 24 hours and 37 minutes—slightly longer than one day on Earth. Because of this, if you observe the planet through your telescope at the same time for several weeks, you will be able to observe different surface areas. Extend your observing times accordingly, especially during the months leading to and after an opposition.

 We hope this guide helped you get better acquainted with Mars. While you are observing our nearest neighboring planet, you may imagine a day in the future when human beings finally step foot on its surface. Do not forget to reflect that there are intelligent rovers already on Mars (both alive and dead) that originated from Earth, plus several orbiters circling the Red Planet, and three more spacecraft that are arriving soon! Perhaps these new missions will unlock more of Mars’ secrets and answer the age-old question, “Is Mars really hiding something?”

To learn more fun Mars facts, please click here.

To browse Celestron telescopes and accessories that will make your Mars viewing experience more enjoyable, please click here.

Have a great time exploring Mars! Clear skies! 

Other articles you might be interested in: Ultimate Guide to Observing the Universe