Skywatch Line for Friday, October 26 through Sunday, October 28, 2018

This is Dudley Observatory’s Skywatch Line for Friday, October 26 through Sunday, October 28, written by Sam Salem.

On Friday, the Sun rises at 7:22am and sets at 5:56pm; the waning gibbous Moon sets at 9:13am and rises at 7:36pm. The Moon is well up in the east by late evening, with the Pleiades above it and Aldebaran, the constellation Taurus’ brightest star, closer to its lower left.

Jupiter, at magnitude –1.7, is getting very tough to catch as it hovers just 4 degrees above the southwest horizon, 45 minutes after sunset. At that time, Saturn, at magnitude 0.5, sits some 19 degrees high in the south-southwest. On Saturday evening, use a telescope to see Saturn’s largest moon, Titan, about four ring-lengths to Saturn’s west. Saturn sits upper right of the Sagittarius Teapot in the south-southwest in late dusk. It’s midway between Mars and Jupiter. Mars, at magnitude –0.8, gleams 25 degrees above the south-southeast horizon. Mars is still an exciting telescopic target, though its disk has shrunk from a maximum of 24.3 arc-seconds last summer to its current diameter of 13 arc-seconds. Mars won’t be this big again until July 2020.

Venus is in its inferior conjunction with the Sun on Friday morning at 10:17am, marking the conclusion of the planet’s long-running evening apparition. Venus is hidden in the glare of the Sun. It will reappear in the morning sky in mid-November.

Uranus reached opposition on Tuesday. This makes this weekend a good one for getting acquainted with this faraway planet. The slow-moving Uranus is a 5.7 magnitude dot residing in Aires, just north of the constellation’s border with Pisces. It is an easy target in binoculars if you know the constellations well enough to see where to start with a finder chart. Uranus was the first planet discovered after the invention of the telescope. British astronomer William Herschel found it with his 6-inch reflector from his home in Bath, England, in March 1781. When Herschel stumbled across Uranus, he mistook it for a comet. Its orbit was calculated after months of observations and the planet’s true nature became apparent. The planet is positioned roughly 2½° northeast of 4.3 magnitude Omicron (ο) Piscium. Uranus is within easy reach of binoculars even under light-polluted skies or with bright moonlight, even though you may have some trouble distinguishing it from nearby stars. With a telescope, Uranus looks like a tiny, pale-green disk. It spans only 3.7 arc-seconds.

The dog-bone-shaped asteroid 216 Kleopatra, with its two tiny moons, will occult an 11.1 magnitude star in Canis Minor during Sunday’s early-morning hours along a path from central Alberta through upstate New York and Long Island. In the case of an occultation, the combined light of the 138 km diameter asteroid and the star will drop by 0.94 magnitude to 11.42 magnitude, which is the magnitude of the asteroid, for almost 10 seconds. Use the Asteroid Occultation link below for more details.

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