This is Dudley Observatory’s Skywatch Line for Friday, July 24, through Sunday, July 26, written by Sam Salem.
On Friday, Sun rises at 5:39am and sets at 8:24pm; Moon rises at 9:59am and sets at 11:09pm.
Comet C/2020 F3 NEOWISE will continue to be visible after sunset this weekend. It’s beginning to diminish in brightness, but you can still see it with your unaided eyes if you have a clear dark sky. The easy way to find the comet in evening is to look for the bright stars Dubhe and Merak high in the northwestern sky. They mark the bottom edge of the Big Dipper’s bowl. Each night, the comet will shift left with respect to the Big Dipper’s stars. This weekend, the comet will sit about 1.5 fist diameters to the lower left of the Big Dipper’s bowl star Phecda.
Plan to look for it 1½ hours after sunset. The comet has been fading a little slower than predicted, however, its increasing altitude every evening.
Mercury becomes visible very low in the dawn this weekend. Mercury remains at about the same height from morning to morning. However, it brightens from magnitude +0.9 last Saturday, to magnitude –0.2 this Saturday. Venus, at magnitude –4.6, rises in deep darkness, about an hour before the beginning of dawn. As dawn gets under way, Venus blazes brightly in the east. Look for Aldebaran, much fainter at 1st magnitude, moving farther away to Venus’s upper right each morning. The Pleiades glimmer farther above Aldebaran. Spot Capella, the bright star much farther to Venus’s upper left.
Mars, at magnitude –0.7, rises due east by about midnight, shining bright orange between Pisces and Cetus. Watch for it to rise below the Great Square of Pegasus. By the dawn, Mars shines grandly high and bright in the south-southeast.
Jupiter and Saturn are at opposition this month. Therefore, they rise around sunset, loom low in the southeast in twilight, and climb higher as the evening grows late. Saturn is 7 degrees to Jupiter’s lower left. Farther to Jupiter’s right, look for the Sagittarius Teapot. The two planets are highest in the south around midnight. On Friday, watch Europa’s shadow and the Great Red Spot transit Jupiter together in a telescope. Europa’s shadow will join the red spot, already at mid-transit, at 1:20am. The spot will vanish around Jupiter’s edge at about 3:40am, leaving Europa’s shadow to complete its passage about 20 minutes later.
The Sagittarius Teapot is in the south these evenings. Find it right of Jupiter and Saturn. With the advance of summer, the Teapot is starting to tilt and pour from its spout to the right. The Teapot will tilt farther and farther for the rest of the summer, or for much of the night if you stay out late. The tail of Scorpius is low in the south soon after dark, lower right of the Teapot by a fist at arm’s length. Look for the two stars close together in the tail. These are Lambda and fainter Upsilon Scorpii, known as the Cat’s Eyes. A line through the Cat’s Eyes points west by nearly a fist-width toward Mu Scorpii, a much tighter pair known as the Little Cat’s Eyes. They’re oriented almost exactly the same way as Lambda and Upsilon. Try to resolve the Mu pair without using binoculars.