This is Dudley Observatory’s Skywatch Line for Friday, April 19 through Sunday, April 21, written by Sam Salem.
On Friday, the Sun rises at 6:08am and sets at 7:42pm; the full Moon occurs at 7:12am; Moon rises at 8:04pm and sets at 6:36am.
Look to the west as evening twilight begins to fade to see Mars, at magnitude 1.6, in constellation Taurus. Mars is noticeably fainter than Aldebaran, Taurus’ brightest star. Both Mars and Aldebaran glow with the same pale orange hue. Mars sets around 11:30pm. Jupiter, at magnitude –2.4, rises around midnight. Jupiter shines fairly high in the south before the beginning of dawn. This is the best time to observe the planet. Set up your scope about two hours before sunrise. At that time you’ll find Antares to Jupiter’s lower right, and the dimmer Sagittarius Teapot a similar distance to Jupiter’s lower left. The Teapot is about the size of your fist at arm’s length. Saturn, at magnitude 0.6, rises around 2am. Saturn is the brightest dot in eastern constellation Sagittarius. Saturn glows pale yellow-white, about 25 degrees to Jupiter’s left or lower left. Venus, at magnitude –3.9, pops up in the east, one hour before sunrise. Easy to miss, is nearby Mercury, which rises just 45 minutes before the Sun.
Saturn now climbs high enough in the dawn sky to potentially offer some enjoyable views. The ideal time to observe Saturn is roughly 5am when the ringed planet is approaching its greatest altitude before twilight becomes overwhelmingly bright. Saturn lies around 20 degrees above the southern horizon at that time. For this low altitude of 20 degrees, the telescopic view will usually be compromised by turbulent seeing conditions. With the ring system currently tilted open almost the maximum amount, you should have little trouble spotting the famous Cassini Division, a 4,700 kilometer wide gap that separates Saturn’s two brightest rings. Under good seeing conditions, this feature is visible even in a small telescope.
Lyrid meteor shower is expected to put forth the most meteors during the predawn hours on Monday and Tuesday. The annual Lyrid meteor shower is active each year from about April 16 to 25. As with most meteor showers, the peak viewing time will be before dawn. That’s when the radiant point, near the star Vega in the constellation Lyra, is highest in the sky. Unfortunately, the waning gibbous Moon, very close to full, will wash out all but the very brightest meteors this year during the peak.
Some religious holidays are scheduled based on the Moon’s phases. Passover and Easter, celebrated this weekend, are scheduled according to full Moon. Passover is celebrated on the first full Moon after the spring equinox. Easter falls on the Sunday that follows the first full Moon occurring on, or, the day after the spring equinox. If the full Moon occurs on a Sunday, Easter is observed the following Sunday. On the other hand, the first day of Ramadan, to be celebrated in a couple of weeks, is scheduled based on the new Moon.