As always, backyard astronomy is convenient but getting out to a darker sky away from buildings, trees and light pollution greatly improves your chances for enjoying the night sky. That having been said, let’s take a look at this weeks night sky.
Tonight, Sunday, September 4.
Facing West – Southwest about 30 minutes after Sunset, look for the thin waxing crescent Moon just 9.6% illuminated. The Moon is waxing toward first quarter later this week. Look about 5° below and to the left of the Moon to see if you can spot the bright star Spica. Looking to the right and below the Moon is Venus shining at magnitude -3.9 just about 5.5° above the horizon. You’ll need a clear, low horizon to see it.
Turn your gaze overhead and watch for the 0.0 magnitude star Vega (alpha Lyrae) to appear. Vega is the first star to appear after sunset this time of year and is in the constellation Lyra the Harp. Vega forms one corner of the summer triangle, a conspicuous asterism of three stars. As the night sky grows darker, around 8:30 PM, look for the 5.0 magnitude star Epsilon Lyrae. Depending on your location, you may need binoculars to spot it. Epsilon Lyrae, when viewed through binoculars, you’ll notice that Epsilon is really two 5th-magnitude stars that lie a little more than 3 arc-minutes apart. Each of these two stars is also double, but you need a telescope to split them. This is the famous double-double star in Lyra.
Monday, September 5.
In late August and early September, the constellations Ursa Major (the Great Bear) and Cassiopeia (the Queen) lie on opposite sides of the North Celestial Pole. Both constellations pivot around the North Star called Polaris (alpha Ursae Minoris). A common misconception is that Polaris is the brightest star in the sky. It is not the brightest star in the sky. That designation belongs to Sirius. Polaris is the brightest star in the constellation of Ursa Minor. throughout the course of the night in early September, these two constellations appear equally high as darkness falls. You can find Ursa Major and its prominent asterism, the Big Dipper, about 30° above the northwestern horizon. Cassiopeia’s familiar W-shape appears the same height above the northeastern horizon.
Thursday, September 8.
Tonight look for the nearly First Quarter Moon to appear about 4° above Saturn. The duo appears in the Southwest 20 minutes after Sunset about 20° high. The scene looks best with the naked eye but don’t pass on the opportunity to view the moon and Saturn through binoculars or a telescope. Both are quite magnificent.
Friday, September 9.
First Quarter Moon occurs at 7:49 a.m. EDT. But wait for nightfall. The Moon appears about 55 percent lit and lies almost 10° above Mars. Mars is worth exploring in detail any night this week with a telescope. Mars shows a 10″ (arc-min) diameter, orange-red disk with a few subtle dark markings.
Observing the First Quarter Moon is always a treat with a small telescope. One word of caution, use a Moon filter. The First Quarter Moon is very bright and a moon filter reduces the glare and increases the contrast. Grab a Moon atlas and explore the Moon’s eastern hemisphere. After a low power view, put in a 10mm eyepiece and take a closer look at the area surrounding Mare Nectaris and the mountains (Montes Caucasus) the lie between Mare Imbrium and Mare Serenitatis. This is one of my favorite targets for Lunar star parties. It’s always a crowd-pleaser.