|
dusk ebbs into darkness. As always, binoculars help out with any Mercury quest.
• Use Great Square of Pegasus to find Comet Panstarrs in March 2013
• If you live at mid-northern latitudes or farther north, and are familiar with the Square of Pegasus asterism, you might be able to locate Mercury with the stars Scheat and Markab. Draw an imaginary line, going downward from Scheat through Markab to locate Mercury near the horizon. Given a clear sky and unobstructed horizon, Mercury should be visible to the unaided eye about an hour or so after sunset. If not, try binoculars.
• Setting times of the sun and Mercury in your sky
• At an elongation of 18o Mercury lies far enough east of setting sun to stay out till after the end of nautical twilight. By definition, nautical twilight ends in the evening sky when the sun is 12o below the horizon. For reference, the sun's diameter equals one-half degree, and your fist at an arm length approximates 10o.
• At dusk, also look in the southern sky for the waxing crescent moon, the dazzling planet Jupiter and Aldebaran, the brightest star in the constellation Taurus. Unlike Mercury, which sets by nightfall, this brilliant threesome stays out till late night
• Because Mercury is setting a maximum amount of time after sunset right now, this is your chance to catch Mercury low in the west at late dusk or nightfall. But don't tarry when seeking this elusive yet surprisingly bright world, for Mercury - even now - follows the sun beneath the horizon by the time that it gets good and dark. At mid-northern latitudes, nautical twilight ends about one hour after sunset, and Mercury sets about one and one-half hours after the sun.
(Continued on page 25)
|
|
