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