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Last updateSat, 11 Jan 2014 11am

Astronomy

Mars and Saturn are easy to spot in the evening sky throughout July; Saturn, with its rings, is a real showpiece for telescopic viewing. Mars will form a close, eye-catching pair with the star Spica for several evenings around July 13.

In the brightening dawn for much of month, brilliant Venus has a companion, Mercury, not far to its lower left.

Especially attractive gatherings of the moon, planets and stars occur on July 5 and 7 at dusk, and on July 22 and 24 at dawn. Dark moonless nights offer excellent views of the Milky Way, best July 1 and 2 after moonset; and in the latter half of month.

July 2014 at dusk: The four brightest starlike objects visible at dusk (excluding Jupiter, barely above the west-northwest horizon at the start of month) are: Arcturus and Vega (both near magnitude 0.0); Mars (0.0 to +0.4); and Saturn (+0.4 to +0.5).

July’s evening planets: Using binoculars, can you spot Jupiter very low in the bright twilight in the west-northwest at the start of month, before it departs? Reddish Mars, in the southwest, passes 1.3 degrees north of blue-white Spica on July 13 in the tightest and last of their three pairings this year. It will be fascinating to follow this colorful pair for several evenings, separated by no more than 5 degrees from July 3-22. Saturn is in the south to south-southwest, 23 degrees to the upper left of the close Mars-Spica pair on July 13.

Saturn’s rings are tipped 21 degrees from edge-on during July (the minimum for this year). This temporary decrease on the way toward 27 degrees maximum in 2017 is caused by our Earth-platform revolving around the sun, affecting our view.

In late July and early August, when Saturn is close to 90 degrees from the sun, telescopes show the best “3-D” appearance of the planet and rings, because we can then best observe the planet’s shadow cast upon the rings. Look for a “gap” where the shadowed portion of the rings goes behind the planet’s northeast limb.

Stars: Regulus, heart of Leo, sinks nearly to the west-northwest horizon at month’s end. Golden Arcturus is high in the south to west-southwest; Spica, the spike of grain in Virgo’s hand, is in the southwest, near Mars; Antares, heart of Scorpius, reaches its high point low in the south. The Summer Triangle of Vega-Altair-Deneb ascends in the east, as befits its name. It’s up all night this month. Find it plotted on both our charts, for dusk and dawn.

Follow the waxing moon in the evening sky as it passes near these planets and bright stars: Regulus on July 1; Mars and Spica on July 5 (a spectacular trio!); Saturn on July 7 (close); and Antares on July 8 and 9.

For evening-planet-watchers this summer: Mars goes from west to east of Spica this month. On July 1, Mars is just more than 5 degrees northwest of Spica. On July 5, the moon, just past first-quarter phase and a little more than half illuminated, will pass between Mars and Spica while they’re within 4 degrees. In a colorful patriotic pairing on July 13, the red planet will pass just 1.3 degrees north of the blue-white star. Mars continues east, ending 14 degrees east of Spica on July 31.

July 2014 at dawn: The five brightest objects are Venus, Mercury (after it brightens past magnitude 0 at midmonth), Vega, Capella and Rigel (after it appears late in the month).

The bright planets can both be found in the east-northeast: Venus, shining nearly at magnitude -4, dominates the morning sky. Mercury is easy to find, especially when it’s within 7 degrees to the lower left of Venus July 12-20.

Stars: The Summer Triangle of Vega-Altair-Deneb, visible all night through July, is high in the western sky at dawn and descends as the month progresses. Fomalhaut, mouth of the southern fish, swims westward low in the south. Aldebaran, eye of Taurus, is just 4 degrees to the south of Venus on July 1 and ascends the eastern sky all month as Venus remains low. Far to the upper left, the “Mother Goat” star Capella ascends in the northeast. Late in month, Betelgeuse and Rigel, shoulder and foot of Orion, emerge above the eastern horizon. (Look midway between them at an earlier stage of twilight for a vertical line of three stars—Orion’s belt!) Farther north, find Pollux (with Castor 4.5 degrees above). Pollux is just more than six degrees north (upper left) of Mercury on July 28 and 29.

The waning crescent moon in the morning sky passes near Aldebaran on July 22 (close), Venus on July 24 and Mercury on July 25 (low in twilight).

Many beautiful sights await you this summer, in both morning and evening skies. Mark Monday, Aug. 18, on your calendar. Be sure to look about an hour before sunrise that morning to catch the spectacular close pairing of the two brightest planets, Venus and Jupiter. The Abrams Planetarium Sky Calendar will provide illustrations of these and other gatherings; find out how to subscribe at www.pa.msu.edu/abrams/skycalendar.

Check the website of the Astronomical Society of the Desert, www.astrorx.org, for dates, maps and directions to our “star parties,” where everyone is welcome to look through our telescopes at the moon, planets and “deep sky objects.” Year-round monthly sessions begin at dusk at Sawmill Trailhead; dates this summer are July 26, Aug. 23, and Sept. 20, as sky conditions permit.

Seize opportunities this summer to enjoy the beauty of the sky!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller, who provided the twilight charts, did graduate work in planetarium science and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.