Abrams Planetarium SKYWATCHER'S DIARY: August 1995 Editor: The Skywatcher's Diary for August 1995 has been prepared by David Nette and Robert Victor. Credit to Abrams Planetarium, Department of Physics and Astronomy at Michigan State University would be appreciated. Our illustrated *Sky Calendar* accompanies the printed version of Skywatcher's Diary as it is sent monthly to Michigan newspapers, but does not accompany this Internet version. If you would like a sample copy, send your request with a self-addressed, stamped envelope to Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, MI 48824. This month's most striking sights include the moon passing near planets and bright stars, on the evenings of August 1, 2, 5, 12, and 29, and the mornings of August 13 and 19. Morning events are mentioned in Skywatcher's Diary one day prior to the event. For observers with telescopes, events involving Jupiter's satellites are described under August 6, 7, 9, 16, 20. The unusual edgewise presentation of Saturn's rings is described under August 8, 10, 13. The Department of Physics and Astronomy at Michigan State University has now made the Skywatcher's Diary available over the Internet. It can be accessed via a World-Wide Web browser such as Netscape or Mosiac, directly at URL: http://www.pa.msu.edu/abrams/diary.html Tuesday, August 1 One hour after sunset the waxing crescent moon is low in WSW. Note first-magnitude Spica 11 degrees upper left, and fainter Mars 7 degrees right of the moon. Mars is 17 degrees lower right of Spica tonight. In coming weeks, watch the red planet creep closer to Spica; on Aug. 28 it will pass within 2 degrees to Spica's upper right. Binoculars are increasingly useful for following Mars and Spica this month as they sink lower in the twilight glow. Wednesday, August 2 An hour after sunset the fat crescent moon, one day before First Quarter, is low in SW with Spica 3 degrees to its lower right. Spica marks the spike of wheat in the hand of Virgo. Mars is in WSW, 19 degrees lower right of the crescent. Thursday, August 3 An hour after sunset the moon is at First Quarter phase in SW. Spica shines 17 degrees lower right of the half moon. Friday, August 4 An hour after sunset the waxing gibbous moon is in SSW with bright Jupiter 11 degrees to its left. The moon travels east an average of 13 degrees daily against background stars. Can you guess where will it appear tomorrow evening at this time? Saturday, August 5 An hour after sunset the moon is just west of due south. It has overtaken bright Jupiter, which appears 3 or 4 degrees to moon's lower right. Antares, the heart of the Scorpion, shines about 7 degrees to their lower left. Sunday, August 6 The moon is in S as darkness falls with bright Jupiter 18 degrees to its right. Antares is within 7 degrees lower left of Jupiter. Using a telescope, try to spot the four Galilean satellites (the four brightest moons of Jupiter). Tonight Io, Ganymede, and Callisto are east of the planet, and Europa disappears behind Jupiter's west edge at 10:59 p.m. EDT. Monday, August 7 The moon is in SSE at nightfall, in the constellation Sagittarius. The eight stars of the Teapot shine below the gibbous moon. Using binoculars at nightfall, locate bright Jupiter in S to SSW and look for the Galilean satellites. Tonight Europa, Ganymede, and Callisto are all at their farthest apparent distances E of Jupiter, and innermost Io is near its greatest possible distance W. Can you see all four? Because of bright moonlight next weekend, the best view of this year's Perseid meteors, with the shower radiant high in a dark moonless predawn sky, may be about two hours before sunrise Tuesday morning. Tuesday, August 8 Three hours after sunset the moon is nearing its high point in the S. Jupiter is then low in SW, and Saturn low in ESE. Tonight and tomorrow night Saturn appears ringless as its rings are nearly edgewise with their dark side tipped very slightly toward Earth. On Thursday afternoon the rings will be exactly edge-on. From that evening until mid- November, the rings' illuminated north face will be tipped increasingly into our view. By mid-October we'll see the rings from 2 degrees above their lighted face. Using a telescope, how soon can you start to detect the rings of Saturn? For the clearest views, remember to look when Saturn is high in the sky. After this week, not until the year 2039 will Earthlings have another chance to view Saturn while the rings are so close to edge-on and the planet is high in the sky. Wednesday, August 9 An hour after sundown the waxing gibbous moon is low in SE. Then turn around to face NW and find the seven bright stars of the Big Dipper. Next, follow the curve of the Dipper's handle to Arcturus, high in WSW, and continue to the lower left, toward Spica. Remember: "Follow the arc to Arcturus, and drive a spike to Spica." Don't confuse Spica with fainter Mars, now 12 degrees to Spica's lower right and closing in. For telescopic observers in eastern and central U.S. tonight, Jupiter's largest satellite Ganymede casts its shadow upon Jupiter. Look for a tiny black dot slowly moving across the northern region of the planet. Be sure to look before 10:20 p.m. EDT (9:20 p.m. CDT), because that's when Ganymede's shadow slides off the face of Jupiter. [A week from tonight, viewers in western U.S. will have their turn.] Thursday, August 10 The Full Green Corn Moon rises in the ESE shortly before sunset. Can you see both Sun and Moon simultaneously? By two hours after sundown, Saturn has just risen between E and ESE, about 30 degrees lower left of the moon. Through a telescope, Saturn's rings appear almost exactly edge-on tonight. Wait several more hours until Saturn rises much higher. Can you detect the rings' shadow as a narrow dark line across the face of the planet? Friday, August 11 Two hours after sunset the waning gibbous moon is in ESE with Saturn 17 degrees to its lower left. Given that the moon travels some 13 degrees eastward daily against background stars, can you predict where the moon will appear tomorrow evening at this time? Saturday, August 12 The moon is low in the E to ESE two hours after sunset. Look for yellowish Saturn, 5 degrees below. Bright moonlight spoils tonight's peak of the Perseid meteor shower. An hour before sunup Sunday the moon is high in the SW with Saturn within 5 degrees to its lower left. Sunday, August 13 Two hours after sundown the moon is just risen in E with Saturn 12 degrees to its right. Through a telescope, Saturn's nearly edge-on rings may appear to the sides of the planet as a very narrow thread of light. For a clear view, wait several hours until Saturn climbs high in the sky. Monday, August 14 The moon rises shortly after the end of evening twilight, allowing a brief dark sky view of the Milky Way and a few Perseid meteors. Each night the moon rises later, giving us a longer "window" of dark skies. Tuesday, August 15 At dusk Mars is low in WSW with Spica, the spike of wheat in the hand of Virgo, 8 degrees to its left and a little higher. Keep watching this pair as Mars closes in on bright Spica; by August 28, they'll be within just 2 degrees! Wednesday, August 16 [Tonight telescopic observers in western U.S. have their turn to see Jupiter's largest moon Ganymede cast its shadow on the planet. Beginning at 8:57 p.m. PDT (9:57 p.m. MDT), look for a tiny black dot slowly moving across Jupiter's northern region.] Four and a half hours after sundown the waning gibbous moon is low, just N of E, with the Pleiades star cluster 17 degrees to its lower left. Thursday, August 17 Four and a half hours after sunset the Last Quarter moon is low in ENE with the Pleiades, or Seven Sisters, 8 degrees to its upper left. At dawn Friday moon is high in SE with ruddy Aldebaran, the eye of Taurus, 12 degrees to its lower left. Friday, August 18 An hour before sunup on Saturday the waning crescent moon is high in ESE, with first magnitude Aldebaran within 2 degrees lower right. The Pleiades shine 13 degrees upper right of the moon. Arabs named Aldebaran "The Follower", because the star follows the Pleiades across the sky. Saturday, August 19 At dusk Mars-Spica are 6 degrees apart and closing, very low in WSW. Mars is the fainter, to the right of Spica. The pair should now just fit within the field of view of 7-power binoculars. Sunday, August 20 Venus is at superior conjunction, hidden in the solar glare on the far side of the Sun. Venus will emerge as an evening "star" in autumn, climbing past Jupiter in mid-November. Tonight Callisto, the outermost of Jupiter's four Galilean satellites, passes beyond Jupiter, but remains visible because the satellite orbits are currently tipped enough to cause Callisto to clear the planet's south polar region. Look in the E an hour before sunrise Monday for the thin crescent moon with Betelgeuse, the shoulder of Orion, 12 degrees to its right. Monday, August 21 At dawn Tuesday the thin crescent moon is in the E, with Procyon, the Little Dog Star, 14 degrees to its lower right. Betelgeuse, the reddish shoulder of Orion the Hunter, shines 20 degrees to the moon's upper right. Sirius, the Dog Star, flashes 27 degrees lower right of Betelgeuse, and nearly as far to the right of Procyon and a little lower. Tuesday, August 22 An hour before sunup Wednesday the waning crescent moon is low in E, with bright Procyon 11 degrees to its lower right. The Gemini Twins, Castor and slightly brighter Pollux, shine to the crescent's upper left. Wednesday, August 23 Look very low, just N of E at dawn Thursday for your last view of the slender crescent old moon. Procyon, the Little Dog star, is 18 degrees to the moon's upper right. Thursday, August 24 An hour after sunset face NW and locate the seven bright stars of the Big Dipper. The two stars in the front of the Dipper's bowl are called the Pointer Stars; a line connecting them, extended one Big Dipper length upper right, points to the North Star, Polaris. This 2nd-magnitude star marks the end of the handle of the fainter Little Dipper. Friday, August 25 New Moon occurs at 12:31 a.m. EDT on Saturday, marking the start of the lunar cycle. The next several nights will be quite dark as the moon sets soon after sunset; take advantage by observing deep sky objects, such as the many star clusters and nebulae in Scorpius and Sagittarius, toward the center of our Galaxy; the Milky Way itself; and Andromeda Galaxy. Saturday, August 26 Tonight through Aug. 30, Mars and Spica are about 2 degrees apart. Look for the pair very low in WSW an hour after sunset. You can tell them apart by Mars' reddish color. Sunday, August 27 [From southern states within half an hour after sunset, binoculars may show a thin crescent moon, very low just south of due west, with Mercury within 4 degrees above it.] The brilliant blue-white star Vega is nearly overhead at nightfall. Nearby are Altair and Deneb, completing the Summer Triangle. Using binoculars on a clear, very dark night, inspect the brightest patch of Milky Way within the Summer Triangle. Stars galore! You are looking into the spiral arm in which we reside within our Galaxy. Monday, August 28 Look early, half an hour after sunset, for the thin crescent moon very low in W. Can you spot the moon with unaided eye? As the moon sets tonight, look 15 degrees to its upper left for Mars passing within 2 degrees north of Spica. Tuesday, August 29 Look for a beautiful gathering very low in WSW at dusk. The thin crescent moon joins Mars and Spica in a very compact group best seen in binoculars. The entire gathering is just over two degrees wide! Wednesday, August 30 At dusk the moon is very low in the SW to WSW. The pair of Mars and Spica, still within 2-1/2 degrees apart, are now to the lower right of the crescent. That glow you see on the moon's dark side is earthshine, resulting from sunlight reflected off the Earth to illuminate the moon. Thursday, August 31 As darkness falls the moon is low in the SW with bright Jupiter 16 degrees to its upper left. Reddish Antares is 6 degrees lower left of Jupiter. Turn to the WSW about 25 degrees to moon's lower right to find ruddy Mars and bright Spica still within 3 degrees apart and separating. ***** end of Skywatcher's Diary for August 1995 *****