Skywatch Line for Friday, October 20, through Sunday, October 22, 2023

This is Dudley Observatory’s Skywatch Line for Friday, October 20, through Sunday, October 22, written by Sam Salem.

On Friday, Sun rises at 7:14am and sets at 6:05pm; Moon rises at 1:40pm and sets at 10:02pm.

On Friday, the Moon, a day short of first quarter, shines low in the south right at the end of twilight. Before the Moon gets any lower, use binoculars to see that it’s sitting almost smack on the four-star handle of the Sagittarius Teapot.

Saturday is the International Observe the Moon Night. It’s a worldwide event for moon-lovers, held annually since 2010. It’s scheduled each northern fall, on a night when the Moon is near the first quarter phase. First-quarter Moon occurs on Saturday at 11:29opm. The Moon is now in the dim area between Sagittarius and Capricornus, almost smack on top of Herman’s Cross, a.k.a. The Dogs, the little four-star asterism. Its stars are all about magnitude 4½ , quite a bit fainter than those of the Teapot’s handle. Use binoculars to help you locate the asterism. Herman’s Cross is 2° from end to end. Observe the Moon with a telescope around quarter-moon when detail is visible on the line between lunar light and dark (day and night). That line is called the terminator. On a first quarter Moon, that’s the line of sunrises, and just as at an earthly sunrise, shadows are longest along the lunar terminator. So lunar features stand out most clearly then. Also, look beyond the terminator for an illuminated mountain peak or crater rim that appears as a speck of light on the dark Moon.

The Orionid meteor shower should be near its peak Saturday night. The good Orionid-watching hours are from about 1:00am. to the first light of dawn Sunday morning. The Moon will have set. This shower is a modest one. In a very dark sky you might see 8 or 10 meteors per hour. The shower’s radiant is in the east at Orion’s dim club, between Betelgeuse and the feet of Gemini.

Venus, brilliant at magnitude –4.6 in the constellation of Leo, shines high in the east before and during dawn. It rises nearly 2½ hours before dawn’s first light. Look before the sky brightens and you’ll spot Regulus, only 1 percent as bright, above Venus. Regulus is 11° over Venus on Saturday morning. Spot Gamma Leonis, or Algieba, a little fainter star, 8° left or upper left of Regulus. It’s a fine binary star for telescopic view. The binary stars are at magnitudes 2.4 and 3.6, with 4.7 arcseconds separation. In a telescope Venus now is half lit.

Jupiter, at magnitude –2.8, in the constellation of Aries, rises in the east-northeast in twilight. It dominates the east later in the evening and shines highest in the south after midnight. It’s on its way to opposition November 2nd.

Saturn, at magnitude +0.6 in dim constellation of Aquarius, is the brightest “star” in the southeast in twilight. It’s highest in the south around 10pm. Fomalhaut twinkles two fists at arm’s length below it.

Uranus, at magnitude 5.6 in the constellation of Aries, is 10° east of Jupiter.

Neptune, at magnitude 7.8 at the Aquarius-Pisces border, is nice and high 25° east of Saturn.