Skywatch Line for Friday, April 18, through Sunday, April 20, written by Sam Salem

This is Dudley Observatory’s Skywatch Line for Friday, April 18, through Sunday, April 20, written by Sam Salem.

On Friday, Sun rises at 6:08am and sets at 7:41pm; Moon rises at 12:49am and sets at 9:03am.

On Friday early morning, the waning gibbous Moon will hang near the asterism of the Teapot of Sagittarius the Archer. On Saturday early morning, the Moon will float inside the stars of the Teapot.

Last-quarter Moon occurs on Sunday night at 9:36pm. The half-lit Moon doesn’t rise until around 3 am. By the very beginning of dawn, roughly an hour and a half later, it’s still low in the southeast in dim constellation of Capricornus and about two fists lower left of the Sagittarius Teapot.

Two planets rise in the evening sky. They will lie along the path the Sun travels in daytime. As darkness falls, look for bright Jupiter high in the western sky and reddish Mars almost overhead. Jupiter will set before midnight by month’s end and Mars will set a few hours later.

Mars, magnitude +0.7 at the Gemini-Cancer border, glows high in the southwest right after dark. It’s still nearly in line with Pollux and Castor to its right. Mars draws a little farther away from them every day. In a telescope, Mars has shrunk to only 7 arcseconds in diameter.

Jupiter, magnitude –2.1 in the constellation of Taurus, shines bright white in the west in early evening, 41° lower right of Mars along the ecliptic. Jupiter continues to form a nearly equilateral triangle with Taurus’s two horn-tip stars, Beta and Zeta Tauri, above it.

Farther below Jupiter shines orange Aldebaran. Farther to Jupiter’s lower right are the Pleiades. Jupiter, Aldebaran, the Hyades, and the Pleiades are getting lower in the west at nightfall. Jupiter sets in the west-northwest around midnight. In a telescope, Jupiter has shrunk to only 34 arcseconds wide.

Venus, magnitude –4.6. rises due east at the very beginning of dawn. Venus will continue to rise right at the start of dawn for all the rest of April and May. In a telescope as dawn grows bright, Venus is a shrinking but thickening crescent. It will become half lit around the end of May.

Mercury and Saturn are barely detectable very deep in the glow of sunrise, but they hide under bright marker, Venus. By Saturday, Venus is a little higher. Saturn by then is 5½° below or lower right of it. Mercury by then has brightened to mag +0.5 but it’s 9° under or lower left of Venus. Try to locate the two planets using a telescope if you have a very flat east horizon.

Right after dark, watch Orion in the southwest, striding down to the right with its belt horizontal. The belt points left toward Sirius and right toward Aldebaran and, farther on, the Pleiades. Above Aldebaran shines bright Jupiter.