A Guide to Observing Mars

Here’s how you can see the red planet at its very best.

HST-2016-Mars

The Hubble Space Telescope captured this view of Mars on May 12, 2016, as the planet neared opposition. The most prominent dark feature is Sabaeus (the horizontal bar at lower centre), which can be seen in backyard telescopes. Courtesy NASA, ESA, the Hubble Heritage Team (STScI/AURA)

The attraction is this: Mars is the only planet that shows us surface detail. Most of the other planets are covered in clouds, while airless Mercury is too small and blurry to ever reveal much.

The most conspicuous Martian features are the planet’s phase (before and after opposition), its bright polar caps, and dusky shadings on it surface. To enhance the subtle dark markings, once thought to be green fields of vegetation, use an orange filter (Wratten #21) or, for big scopes, a red filter (#25) in your eyepiece. To enhance any blue or white clouds and the polar caps, use a pale blue filter.

Mars series

This sequence of illustrations shows one complete rotation of the planet. (The Martian central longitude is noted below each disc.) North is up.

Any telescope will work for Mars, but the bigger, the better. A 4-inch refractor or a 6-inch reflector are the recommended minimum. Apply high power (175× or more), and wait for a night with steady seeing, when the Martian disc is not blurred by turbulence in our atmosphere. Also, as inconvenient as it might be, plan to observe late at night, when Mars sits high in the south above the worst effects of our atmosphere. And keep in mind that the Martian surface features are much more subtle than typically shown in photographs.

Mars by Andrew Kwon

Andrew Kwon took this detailed image of Mars from his observatory in Mississauga, Ontario, on February 12, 2014, nearly two months before opposition. Although the Martian disc was only 9.9 arc seconds in diameter, his image reveals substantial surface detail, including the shrinking northern polar cap.

This year’s opposition is very good, but an even better one happens in 2018, when Mars will reach 24.3 arc seconds across in July. That’s less than one arc second shy of its record close approach of August 2003, when thousands of observers lined up at telescopes the world over to see the red planet at its best.

Mars Opposition Diagram

The minimum distance in astronomical unites (AU) and maximum disc size in arc seconds (“) are given for each opposition. SkyNews diagram.

For detailed information and charts pertaining to the current Martian apparition, see This Week’s Sky and the May/June issue of SkyNews, pages 33 to 35.

Categories: Moon and Planets
2 comments on “A Guide to Observing Mars
  1. Roger Woloshyn says:

    A very well written article – informative and to the point. I really do appreciate Alan Dyer’s work, especially his reports from Churchill on the northern lights. Keep up the good work. Photography is excellent.

  2. Brian Woolley says:

    I took my first look at Mars 4 weeks ago through my 19mm eyepiece/10 inch Meade. Mars seemed quite small. I’ll use a higher magnification in 3 weeks and see how the view changes. Thanks Alan.

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