Wednesday, September 29 2010 @ 11:42 am EDT
Contributed by: dgrosvold
By Wednesday, the Moon will not rise until 11:03 PM CDT, late enough that the glare will no longer interfere with evening observing. The Moon reaches Last Quarter at 10:53 PM CDT on Thursday evening, though it will not rise until after midnight. Moonrise occurs about an hour later each night.
Wednesday evening, 103P/Hartley lies in the north-northeast, in the constellation of Cassiopeia, the Beauty Queen, approximately 0.87 above Zeta Cassiopeiae. Over the course of the week, Comet Hartley 2 will track down to the southwest, as shown in the finder chart. At magnitudes dimmer than 5, you will need binoculars or a small telescope to see Comet Hartley 2 in any but the darkest of skies.
In late evening, as Jupiter rises high in the southeast, look for Fomalhaut, (pronounced FOAM-a-lot, or less commonly, FOAM-al-howt.) Fomalhaut is known as the Autumn Star, sparkling far to Jupiter's lower right in the south-southeast. The name Fomalhaut means "the mouth of the whale" in Arabic, and it is the brightest star in the constellation Piscis Austrinus, the Southern Fish.
Even though Venus is at its brightest now at magnitude –4.8, it is becoming a thin, long crescent. Venus is sinking very low in the southwest during bright twilight, setting well before dark ahead of Mars, 6.5° to Venus's upper right all week. That's about one field-of-view width in a typical pair of 7 x 50 binoculars, which you'll definitely need to spot either of them.
Mercury is still very bright at magnitude -1, and is a fine morning target for planet watchers. Once again this week, look for it low in the east about 45 minutes before sunrise. It sinks lower as the week advances, getting lost in the glare of the sun by mid-next week.
Hiding in Hercules is one of the most beautiful jewels of the night sky, the Great Cluster in Hercules (M 13,) the brightest globular cluster in the northern hemisphere. M 13 lies two-thirds of the way along the longest side of the Keystone asterism, a quadrangle in Hercules formed by the stars Pi (π,) Eta(η,) Zeta(ζ,) and Epsilon (ε) Herculis. Look about mid-way up to the zenith in the west-northwest for the Keystone, and then look to the north end of the longest side to find M 13,in a clear dark sky, it should be visible as a fuzzy patch slightly larger than a star. A telescopic view reveals a myriad of stars swarming around in a big ball — about a hundred thousand of them in all. M 13 is a spectacular sight on a crisp clear night like the ones we'll have this week, and should not be missed.