A lot is going on in the sky this month, including a beautifully-paired conjunction of radiant Venus and the crescent Moon low in the western twilight on the 15th, and the Moon hovering just above Jupiter on the 20th in the southwest at dusk. (That date is also “Moon Day”—the anniversary of the first landing on another world by human beings in 1969 by the crew of Apollo 11.) But the big event in July is the close approach of Mars, being nearer to us than it ever will be until 2035!
Approximately every 26 months, Mars comes to “opposition” with the Sun as seen from the Earth—at which time it rises in the east as the Sun sets in the west. Even so, its minimum separation from us varies considerably due to Mars’ very elliptical orbit. This month the “Red Planet” (it’s actually orange) comes to within 36,000,000 miles of us.
For contrast, when it’s on the other side of the Sun from us, that figure is some 250,000,000 miles!
Opposition this month occurs on the night of July 26th-27th, at which time the Moon is also in opposition (as it always is when full) and will stand above Mars itself. The actual closest approach of Mars to the Earth will happen a few nights later on the 30th-31st. But it will still be a spectacular sight from the end of June as it approaches until September as it recedes, appearing a dazzling golden-orange (some may see it as reddish) that will attract attention anytime the sky is clear during that period. To the unaided eye, it will shine with a steady light (as do all of the planets due to their subtle disks) as opposed to the stars (which are essentially pinpoints and twinkle due to atmospheric turbulence).
Binoculars will offer an interesting view. At 7x to 10x it will be obvious the Mars is not star-like. Image-stabilized glasses will make this even more obvious. Higher power ones (including zoom models) at around 15x to 20x will begin to show the planet’s disk itself. But to really enjoy the spectacle, a telescope is necessary! A combination of aperture and magnification will give varying views. Even a 2.4- or 3-inch refractor at 100x will show one of the white polar caps, the orange deserts, the bluish-green dark markings, and perhaps occasional clouds, given good seeing (steady skies). The larger the scope, the more resolution it delivers and the more detail it will show. For many types of viewing (such as star clusters and galaxies) low powers and wide fields of view give the best results—but when it comes to planets, high powers are in order! Push the magnification up as high as atmospheric turbulence will permit (typically 200x or more). Scientifics offers an excellent selection of sizes, types, and prices (including binoculars too). Check online at www.scientificsonline.com under “astronomy,” “telescopes,” and “binoculars.”
— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing. His latest, Celebrating the Universe!, is available from HayHouse.com.