THE SOUTHERN HEMISPHERE IN JULY
JULY HIGHLIGHTS
Mars is at opposition this month, giving us our best views since August 2003. For July and August the Martian disc will be greater than 20 arcseconds, peaking at 24 minutes on 27 July, when even small telescopes will give good views of its southern polar ice cap and the features associated with plains, valleys and mountains. Its negative declination ensures observers in the Southern Hemisphere see the Red Planet culminate high in the sky, minimising atmospheric
STARS AND CONSTELLATIONS
The constellation of Lyra, the Harp, is low in the northern sky. It consists of four 3rd and 4th magnitude stars arranged in a narrow parallelogram with its brilliant naked-eye alpha star, Vega, a couple of degrees southwest. As well as being the fifth brightest star in the sky (mag. 0.0), Vega is also the closest bright star to the solar apex (9° to the south). This is the position in the sky the Sun is currently heading towards as it continues its 230 million year orbit of the Milky Way.
THE PLANETS
In July all five naked-eye planets are visible in the early evening. Starting in the west-northwest, Mercury has one of its best evening returns, setting just after the end of twilight for most of the month (don’t confuse it with the nearby star, Regulus). Directly above is the beacon of Venus, with brilliant Jupiter due north in Libra. Turning to the east you’ll find Saturn near the lid star of Sagittarius’s Teapot. Finally, luminous Mars, which for a few months is outshining Jupiter, is rising in Capricornus.
DEEP-SKY OBJECT
This month we visit Ophiuchus, the Serpent Bearer. IC 4665 (RA 17h 46.3m, Dec +5° 43’) is a large bright (mag. +4.2) open star cluster comprising around 30 stars ranging from 7th to 9th magnitude. Spanning 1° of sky, its members are well scattered, looking great in binoculars sitting beside Beta Ophiuchi (1° away). This mag +2.8 star helps make up the large ‘Coffin’ asterism. Inside this casket are two globular clusters visible as fuzzy stars in the same binocular field, NGC 6254 or M10, pictured, (RA 16h 57.1m, Dec. -4° 06’) and 3° to its northwest, NGC 6218 (M12). They are of similar brightness with vivid central cores. An interesting difference is that M12’s halo is much more loosely packed than M10’s with stars (mag. +12) well resolved, even close to the core.