The Moon visits Mercury at dawn and Venus at dusk.
Three planets adorn the evening sky, but you have to look early—and fast—to sight Venus, the brightest one. Although it’s climbing a bit higher each week, the –3.9 magnitude evening “star” is still very low in the west-southwest shortly after sunset. Planets number two and three are much easier. Saturn shines at magnitude 0.5 and is positioned roughly six degrees north of Antares, in the southwest. The ruddy-hued star is ½ magnitude fainter than Saturn. Can you detect the difference? Easternmost of the evening worlds is Mars, which is drifting away from the Saturn/Antares duo. The red planet is now magnitude 0.0 and residing in Sagittarius, just above the spout of the Sagittarius Teapot. Early risers can spot a fourth planet: Mercury. The celestial speedster is reasonably well placed in the morning sky. Rising due east nearly 1½ hours before the Sun, it appears as a –0.5-magnitude point of light in Leo. Catch it while you can!
Jupiter is in conjunction with the Sun today, marking the end of one apparition and the start of another. The big planet will begin to emerge from morning twilight in mid-October.
Mercury is at greatest elongation from the Sun (18 degrees in the morning sky) today. This is the planet’s third, and best, morning apparition of 2016.
This morning a razor thin crescent Moon lies just a little more than one degree below Mercury at dawn. You’ll need a clear view to the east to catch this conjunction, but it should be a fine sight in binoculars or with your eyes alone.
The Moon is new today at 8:11 p.m., EDT.
This evening it’s Venus’s turn to receive a visit from the crescent Moon. The two are visible together low in the west during twilight. The lunar crescent will be positioned roughly four degrees above the planet, so both will fit into the field of view of ordinary binoculars.
The new Moon and (hopefully!) not-too-cold autumn weather over the September 30 – October 2 weekend are an invitation to do some deep-sky observing. One object that always makes me glad fall has arrived is the famed Double Cluster in Perseus. In spite of their prominence, the side-by-side clusters didn’t make into Charles Messier’s well-known list of non-comets. The eastern and western clumps of stars are catalogued, respectively, as NGC884 and NGC869.
To really appreciate the Double Cluster, you have to be able to see both halves at the same time. That means using an instrument capable of providing a field of view around two degrees across. Less than that and the glittering duo begin to lose some of their splendour. This is one example of small telescopes having the advantage over big-aperture light buckets. Even binoculars provide a wonderful view of the Double Cluster and its surroundings. After soaking in the wide-field perspective, try inspecting the component clusters individually with your telescope at moderate magnification. Each cluster is rewarding in its own right and it’s fun to compare them. Which one appeals to you more? And don’t forget to note the striking sprinkle of orange stars scattered among the ice-blue cluster gems. Sights like these make the end of summer just a bit easier to take.
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