Observing Mars with a Telescope

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This article was written by Stefan DuBois,
volunteer for The Mars Society

It is licensed under Creative Commons BY-SA 3.0 and may be freely shared, but must include this attribution.
Photograph of Mars taken by the Hubble Space Telescope in 2016. Click to enlarge and view the visible features which have been labeled.
Mars as it appears through a small telescope at 150x magnification.

Mars constitutes the only planet in the solar system with surface features easily distinguishable from Earth—of the inner planets, Mercury’s small size and proximity to the sun make viewing exceptionally difficult, while Venus’ surface hides behind a thick layer of clouds.[1] As such, Martian surface features have long captured the imagination of astronomers, even helping lead to the longstanding popular belief of its inhabitation by extraterrestrial civilization. In 1877, Italian astronomer Giovanni Schiaparelli began mapping areas on Mars, including long, dark lines he named “channels”, or “canali."[2] Mistranslations of this word to English “canals” along with his own observations encouraged American Percival Lowell to theorize that these dark lines were the work of intelligent beings attempting to irrigate their dying planet.[3] Although these lines were soon after revealed to be an optical illusion resulting from the mind’s attempts to connect dark areas at the extent of its vision,[4] even amateur astronomers can make out a variety of other surface features with the aid of a telescope.

When can Mars be seen?

Chart depicting the progression of Mars through the zodiac constellations at three-month intervals over a period of 10 years. Gaps in the sequence indicate when Mars is too close to the Sun to be seen.
Diagram illustrating the relative positions of Earth and Mars at opposition and conjunction. The two planets reach opposition roughly once every 26 months.

Timing plays an essential role in viewing Mars from Earth. The differing orbits between the two planets mean that Mars enters opposition—that is, the point where it and Earth are on the same side of the Sun and therefore at their closest approach—once every 26 months.[1][5] For the majority of the year, Mars appears fairly small in the sky, although not so small that it is invisible to the naked eye. During a window of several months before and after opposition, however, it appears brighter and large enough to make out surface features with the help of a telescope.[1]

  1. ↑ 1.0 1.1 1.2 Landers, Z. (2019, June 15). Viewing Mars With Your Telescope—Extensive Guide. Retrieved September 15, 2019, from Telescopic Watch website: https://telescopicwatch.com/viewing-mars-with-telescope/
  2. ↑ Canright, S. (2009, April 13). NASA - The “Canali” and the First Martians [Learning Materials]. Retrieved September 15, 2019, from NASA website: https://www.nasa.gov/audience/forstudents/postsecondary/features/F_Canali_and_First_Martians.html
  3. ↑ Milner, R. (2011, October 6). Tracing the Canals of Mars: An Astronomer’s Obsession. Retrieved September 15, 2019, from Space.com website: https://www.space.com/13197-mars-canals-water-history-lowell.html
  4. ↑ Evans, J. E., & Maunder, E. W. (1903). Experiments as to the actuality of the" Canals" observed on Mars. Monthly Notices of the Royal Astronomical Society, 63, 488-499.
  5. ↑ Sparrow, G. (2013). Constellations: A Field Guide to the Night Sky (First). Quercus.
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