This is Dudley Observatory’s Skywatch Line for Friday, August 3 through Sunday, August 5, written by Sam Salem.
On Friday, the Sun rises at 5:49am and sets at 8:14pm; Moon sets at 12:20pm and rises at 11:51pm. Last quarter Moon occurs on Saturday at 2:18pm. Once the last quarter Moon is well up, spot the Pleiades to its left and Aldebaran, the brightest star in constellation Taurus, below the Pleiades.
Venus, at magnitude –4.3, loses a little altitude each week. Jupiter, at magnitude –2.1, sets around midnight. Saturn, at magnitude 0.2, reaches transit altitude at roughly 10:15pm. Mars is at its peak brightness and size for the current apparition. This week, the red planet is closer to Earth than it has been in 15 years. Mars glows at magnitude –2.8, twice as bright as Jupiter. The Martian disc spans 24.3 arc seconds. Mars culminates around 12:30am, which is when it’s best placed for telescopic inspection. Recent reports suggest the Martian dust storm may be starting to settle, providing a reason to be optimistic about telescopic observing of Marian details.
The Lagoon Nebula, M8, and its associated star cluster, lies less than 3° to the lower right of Saturn this week. The Lagoon is the brightest emission nebula of the summer skies. In a dark sky it’s obvious to the naked eye as a small Milky Way patch above the spout of the Sagittarius Teapot. The constellation of Sagittarius features the bright heart of the Milky Way and is rich with star clusters and nebulas. The Small Sagittarius Star Cloud, M24, is one of the most eye-catching objects there. Although it’s made up of an uncountable number of stars, M24 isn’t a cluster so much as an isolated patch of the Milky Way, M24 wouldn’t be considered an individual object at all if it wasn’t surrounded by dark nebulas. M24 is a striking sight in binoculars more than by a telescope. High magnification diminishes the Star Cloud’s visual impact. However, scanning M24 with a scope is the best way to explore the network of dark nebulas that frame the faux cluster.
There are plenty of prominent double stars to enjoy this weekend. Albireo is one of the season’s prettiest. The double star is easy to find. Situated in the constellation Cygnus, Albireo marks the foot of the Northern Cross. The Northern Cross is a prominent asterism that consists of the brightest stars in constellation Cygnus, the Swan. The head of the cross is Deneb, the brightest star in Cygnus. The foot star is Albireo. Albireo’s component stars are both reasonably bright, shining at magnitudes 3.4 and 4.7. You’ll have no trouble spotting them in any telescope, even in strong moonlight. The Albireo pair is a wonderful telescopic sight because of their contrasting colors. The bright primary star is a golden yellow, while its companion is a pale, icy blue. Yellow-orange stars tend to be relatively cool compared with bluish-white ones.