Saturn is the brightest object in the southern sky at nightfall at the moment. It forms a very wide pair with Antares, a bright, red-hued star one magnitude fainter than Saturn. At 11 p.m. local daylight time, Antares stands due south with Saturn a fist and a half (15°) to its east or left.
The bright planets and the moon can be very useful in finding fainter things. Inside a 10° wide circle centered on Saturn a rich assortment of deep sky objects visible to both the naked eye and binoculars beckons. They include a prancing horse of interconnected dark nebulae, a bright open cluster, several nebulae and a stunning star cloud 10,000 light years from Earth. Some regions of the sky are sparse, but not Saturn’s present location in the heart of the Milky Way. Like a trip to the downtown of a big city, no matter where you turn, there’s something that catches your eye here.
Before the bright moon returns and spoils the fun, head out to the countryside and dark skies with a pair of binoculars for a look. Don’t forget the bug spray! A telescope will give even better views but isn’t necessary. You can see everything I’m about to describe with binoculars. Wide-field types are the best, the better to take in the grandeur of the scene.
Serendipitously, Saturn is seated on the back of the Galactic Dark Horse, a large collection of dark nebulae some 10° long by 7° wide that bears a striking resemblance to a prancing horse. Dark nebulae are vast clouds of cold dust and gas spewed by generations of aged stars and supernovae. They’re dark because no star or stars are nearby to illuminate them; instead we see them silhouetted against the more distant stars of the Milky Way, which they block from view.
Dark nebulae may appear like a whole lot of empty, but they’re anything but. Mostly invisible to the eye, denser pockets of material within their inky billows are collapsing under the force of gravity to birth new stars and star clusters. The Orion Nebula used to be wholly dark, but stars born there as recently as 30,000 years ago now cast their light into its dark recesses.
The Dark Horse is faintly visible as a soft-edged dark space around Saturn. Probably the easiest parts to see are the lower leg and rump. Use averted vision, the technique of playing your gaze around an object rather than staring squarely at it. With a dark sky and patience, I was able to see almost the entire horse without optical aid. Binoculars will make a big difference, especially if they’re 40mm (ie. 8×40, 7×50, 10×50) or larger. Avoid high-magnification! The horse is so big, it’s best with a magnification of just 7-10x.
The best time to view these Milky Way gems is in late June from 11 p.m. to 1 a.m.; mid-July from 10 p.m. to 1 a.m. and mid-August from 10-11 p.m. Start at Saturn, and after you’ve explored the Dark Horse, slide east about 1.5 fields of view (the circle view you see when holding the binoculars to your eyes) to the east (left) to find the bright, sparkly open star cluster M23. Drop down a field to the Lagoon Nebula, an obvious knot of haze with several embedded stars, and the much smaller Trifid, a short distance above it. Just east of the Trifid, look for the small star cluster, M21.
If you continue east from the nebulae, you’ll run into the magnificent Small Sagittarius Star Cloud. Measuring about 1½° across, its real diameter is 600 light-years, and it resides within the Sagittarius spiral arm an incredible 10,000 light-years from Earth. Binoculars and telescopes break it up into spangles of faint stars blotted here and there by several small dark nebulae. Further east and north, you’ll spy the loose open cluster, M25 and the fuzzy blobs of the Swan and Eagle Nebulas. Their names come from their shapes, which are best viewed in a modest telescope.
With Saturn’s help we can explore the riches of the southern Milky Way this summer, visiting places thousands of light years from home. Happy trails!