****************************************************** Abrams Planetarium SKYWATCHER'S DIARY April 1997 ****************************************************** The Skywatcher's Diary for April 1997 has been prepared by Robert C. Victor. Credit to Abrams Planetarium, Department of Physics and Astronomy at Michigan State University, together with mention of our Sky Calendar, would be appreciated. A sample current issue of Sky Calendar is available over the Internet. It can be viewed via a World-Wide Web browser such as Netscape or Mosaic, directly at: http://www.pa.msu.edu/abrams/apr97skycal.html If you would like a printed sample of the April issue, send a long, self- addressed stamped envelope to: April Sky Calendar Abrams Planetarium Michigan State University East Lansing, MI 48824 Each month, the Department of Physics and Astronomy at Michigan State University also makes Skywatcher's Diary available over the Internet. It can be accessed via a World-Wide Web browser such as Netscape or Mosaic, directly at URL: http://www.pa.msu.edu/abrams/diary.html The Skywatcher's Diary is also available via anonymous ftp at: www.pa.msu.edu in the directory /pub/swd ****************************************************** Comet Hale-Bopp in evening sky: Best dates for viewing the comet right at nightfall, with Moon absent: April 1-7. Nearly as good: April 8- 14, with Moon waxing from thin crescent to half full. By nice coincidence for most of U.S., the comet attains peak altitude about 20- 25 degrees up in NW to WNW at nightfall in first or second week of April. For more information, try some of our favorite Hale-Bopp Web sites: http://encke.jpl.nasa.gov/ http://newproducts.jpl.nasa.gov/comet/ http://medicine.wustl.edu/~kronkg/1995_O1.html http://cfa-www.harvard.edu/cfa/ps/pressreleases/HaleBopp.html http://www.skypub.com/comets/comets.shtml Our own H-B visibility site: http://www.pa.msu.edu/abrams/hbeve.html Obtain Comet Hale-Bopp positions at nightfall for your own location, calculated by the US Naval Observatory: http://aa.usno.navy.mil/AA/data/docs/HaleBoppProg.html To enhance your enjoyment of Comet Hale-Bopp, we recommend these engaging and very readable books: Comet of the Century: From Halley to Hale-Bopp, by Fred Schaaf, and Everybody's Comet: A Layman's Guide to Comet Hale-Bopp, by Alan Hale. For reviews of these and other books on Comet H-B, see February Sky & Telescope magazine or point your Web browser to: http://www.skypub.com/comets/hb10.html Correction to speed of comet stated in Skywatcher's Diary, March 31 Comet Hale-Bopp reached perihelion (closest to Sun, 85 million miles) and attained maximum orbital speed of 44 kilometers per second, or 98,500 miles per hour. ****************************************************** April 1997 Highlights: Comet Hale-Bopp, still near peak brilliance in early April at possibly brighter than magnitude zero, remains in evening sky all month! If you observe comet just before end of twilight, you'll catch it highest in NW on April 3 from latitude 49¡ N (northern tier of contiguous 48 states), to April 15 for S Florida, April 17 for Hawaii. Darkest evenings in late twilight this month, with Moon absent, or no more than half full, are April 1-13 and 24-30. Seen from latitude 40¡ N, Comet Hale-Bopp sets 4 hrs after sunset April 14, and one-half hour closer to sunset with each passing week. By May 13, H-B sets at nightfall. Use Sky Calendar boxes for April 3, 13, 24, and 8-10, and the map, April Evening Skies, to identify stars near the Comet and to follow its motion against the stars. Changes in Hale-Bopp's position from one night to the next will be readily apparent April 1-3, 8-11, and 18-20, as it passes close to stars of 2nd and 3rd magnitude. Comet's motion slows from 1.6¡ per day early in month to 1.0¡ per day near month's end. On April 10, a spectacular occultation of Aldebaran by Moon is visible naked eye and binoculars in far West. Star disappears behind dimly Earthlit leading edge of Moon Vancouver at 9:34 p.m., S.F. Bay area at 9:47 p.m., Los Angeles at 9:53 p.m. PDT. Brightest evening planet: Mars in ESE to SSE at dusk. Brightest morning planet: Jupiter in SE at dawn. ********* SKYWATCHER'S DIARY: APRIL 1997 ********* Tuesday, April 1 At nightfall locate Comet Hale-Bopp in NW and notice the 2nd- magnitude star two degrees to its left. Look nightly to follow the comet's motion against the stars. On Wednesday an hour before sunrise the fat crescent Moon is in SE with bright Jupiter to its lower left. Comet H-B is very low in NNE. Wednesday, April 2 Today Venus is at superior conjunction, hidden on the far side of the Sun. By the end of this month it will be visible to sharp-eyed observers shortly after sundown in bright evening twilight. In NW at nightfall, Comet Hale-Bopp passes 1.5 degrees above the 2nd-magnitude star Gamma Andromedae, forming a celestial exclamation point! Thursday, April 3 At nightfall Comet H-B is in NW, with Gamma in Andromeda 2 degrees to its lower right. On Friday April 4, an hour before sunrise, a thin crescent Moon is in ESE with bright Jupiter 18 degrees to its upper right, in the southeast. Friday, April 4 This weekend, seen from northern U.S., both Mercury and Comet Hale-Bopp are at their highest in the evening sky for the year. Look for Mercury about 45 minutes after sunset, very low, between W and WNW. The comet is 27 degrees to Mercury's upper right as the sky darkens. The Pleiades cluster is about 25 degrees upper left of the comet and Mercury. On Saturday about 45 minutes before sunup, the thin Moon is very low, nearly 10 degrees south of due east. With two days until New, this is your last easy chance to see the old crescent. Saturday, April 5 As the evening sky darkens, locate Comet Hale-Bopp in WNW to NW. Note Mercury 27 degrees to its lower left. Tonight the 2nd-magnitude star Gamma in Andromeda is 5 degrees lower right of the comet, and Algol (Beta in Perseus) is 7 degrees to comet's upper left. Against background stars, Comet shifts 1.5 degrees daily tonight through April 10. Sunday, April 6 Daylight saving time begins at 2:00 a.m. Have you set your clocks ahead one hour? This change will result in later times of sunrise and sunset, by our clocks. Monday, April 7 New Moon occurs today at 7:02 a.m. EDT. or 1:02 a.m. in Hawaii. A very young crescent Moon, just 18 hours old, is possible to see from Hawaii. Using binoculars 20 minutes after sunset, look 11 degrees lower left of Mercury. North Americans will have to wait until Tuesday evening for their first look at the evening crescent. Tuesday, April 8 The young crescent Moon is very low, just N of W, at dusk. Mercury, still brighter than first magnitude but fading fast this week, is 7 degrees to Moon's right. Comet Hale-Bopp is 25 deg upper right of Mercury. Within 3 deg upper left of comet, note 2nd-mag Algol. Wednesday, April 9 At nightfall tonight and Thursday, Comet Hale-Bopp is in a lovely configuration with Algol and a 3rd-magnitude star close by. Note Mercury far to Moon's lower right and Aldebaran far to Moon's upper left. Be sure to look again Thursday, when Moon will be very close to Aldebaran and even cover up the star as seen from western U.S. and Canada. Thursday, April 10 Both the Moon and Comet Hale-Bopp are in beautiful fields for binoculars this evening. Depending on the curvature of the comet's dust tail, observers in Europe and eastern North America may see the 2nd- magnitude star Algol shining through the tail or near its edge. Observe the comet for a couple of hours, and watch its motion relative to the star. At nightfall the Moon is among the stars of the Hyades, with the first- magnitude star Aldebaran above the gathering. Later in evening westerners will see the Moon's faintly earthlit leading upper edge occult, or cover, Aldebaran. From Vancouver the disappearance is at 9:34 p.m. PST; farther down the West Coast, in Los Angeles, the disappearance occurs at 9:53 p.m. For more, see the January and April issues of Sky & Telescope. Much additional information and times for several cities are given at the websites: http://www.skypub.com/whatsup/9704alde.html and http://www.sky.net/~robinson/iotandx.htm Friday, April 11 As sky darkens, note Aldebaran, eye of Taurus, far to Moon's lower right. Moon has shifted 13 degrees eastward against the stars since 24 hours earlier. Saturday, April 12 The bright reddish star Betelgeuse is to Moon's lower left at dusk. Sunday, April 13 Between tonight and Monday evening, the Moon passes First Quarter phase, when it will be 90 degrees east of the Sun and appear half full. Tonight the Moon is a fat crescent and is west of a line connecting Procyon and Pollux. By tomorrow evening, the Moon will appear slightly more than half full and will have moved east of the Procyon- Pollux line. Monday, April 14 From latitude 40 degrees north, Comet Hale-Bopp now sets 4 hours after sunset and about half an hour closer to sunset with each passing week. From all northern latitudes, the best time to observe the comet is right at nightfall, when the comet is highest in a dark sky. Tuesday, April 15 The gibbous (more than half full) Moon continues brightening each night until it's full a week from tonight. Comet Hale-Bopp is so bright that at least its head and bright inner tail will remain visible, even when the sky is flooded by full moonlight a week from now. Look in WNW at nightfall for a bright fuzzy "star" with a fainter tail curving to upper right. For a timetable for viewing the comet, set your Web browser to one of these sites: http://www.pa.msu.edu/abrams/hbeve.html http://aa.usno.navy.mil/AA/data/docs/HaleBoppProg.html Wednesday, April 16 The Moon is high in south just over an hour after sunset, with Regulus, heart of Leo, about 8 degrees to the Moon's east (left). Bright Mars is 18 degrees to lower left of Regulus. For rest of April, Comet Hale-Bopp remains about 20 degrees below or lower left of Capella, the bright "Mother Goat" star well up in WNW to NW at nightfall. Thursday, April 17 Moon is high in SSE an hour after sunset. Regulus is 6 degrees to Moon's upper right, and bright Mars is 13 degrees to Moon's lower left. Friday, April 18 The waxing gibbous Moon is well up in SE at dusk, with bright Mars just 4 degrees upper left. Regulus is 17 degrees to their upper right, and Spica 37 degrees to their lower left. Saturday, April 19 An hour after sunset, Moon is in SE, with Mars 12 degrees to its upper right and Spica 25 degrees to Moon's lower left. Look also for Arcturus in east, 33 degrees upper left of Spica and nearly 40 degrees to Moon's lower left. Compare brightness of Mars and Arcturus in coming weeks. Mars is fading, and by late in May it will be fainter than Arcturus. At nightfall, Comet Hale-Bopp is in WNW, 20 degrees below Capella from northern U.S., or to the star's lower left for the rest of the country. Look for the 3rd-magnitude star Zeta in Perseus only 1.5 degrees to lower left of the comet's bright head, and the Pleiades star cluster 9 degrees to the comet's lower left. Binoculars give the best views. Sunday, April 20 An hour after sunset, face SE to see Spica 13 degrees to Moon's lower left, and bright Mars 24 degrees to Moon's upper right. When the sky darkens, look for the 3rd-magntude star Zeta Persei within 2 degrees below the comet. Our view of the comet will improve this Thursday, when there'll be a brief window of darkness before the Moon rises. But the comet is getting lower each night, and will sink into bright twilight in May. Monday, April 21 With one day until Full, the Moon is in ESE to SE as sky darkens, with Spica, the "Ear of Wheat", within 4 degrees lower right. Spica marks the spike of wheat in the hand of Virgo. Tuesday, April 22 For most of the U.S., the Full Moon rises south of east within a few mintes before or after sunset. At nightfall, Moon is in ESE with first- magnitude Spica 13 degrees upper right and zero-mag. Arcturus 30 deg. upper left. Algonquians called April's Full Moon the Sprouting Grass Moon, Egg Moon and Fish Moon.Even though the moon lights the entire sky, Comet Hale-Bopp can still be found in WNW at nightfall, 20 degrees lower left of zero-mag. Capella. Wednesday, April 23 Note the direction and time of sunset, then watch for the Moon rising at the opposite point of the horizon one hour later. If you're in the right part of the country, listen for the beautiful sounds of toads and frogs. Thursday, April 24 When the sky first gets very dark (about 1-1/2 hours after sunset from northern U.S., earlier from southern U.S.), locate Comet Hale-Bopp in WNW, 20 degrees lower left of the bright star Capella. Binoculars give a good view of the tail, and of the Pleiades star cluster 9 degrees below the comet. Note Aldebaran 14 degrees left of comet and Pleiades. About 2 hours after sunset, Moon rises in ESE and brightens entire sky, spoiling the view. One to two hours before sunup on Friday, the waning gibbous Moon is in SSW, with Antares, heart of Scorpius, within 10 degrees lower left. Friday, April 25 Now that the Moon rises late, about 3 hours after sunset tonight, Comet Hale-Bopp is in very good view early in the evening. Catch the best view of the comet low in WNW right at nightfall, when it's at its highest in a dark sky. The comet is getting lower each night and will soon be gone, so take advantage of any clear skies that come your way. Saturday, April 26 At nightfall, Comet Hale-Bopp is low in WNW, 20 degrees lower left of the bright zero-magnitude star Capella. Look also for first-mag. Aldebaran, eye of Taurus, 12 degrees lower left of comet, and 2nd- mag. Elnath, the Bull's northern horn, 13 deg. to comet's upper left. Far to left of the comet, look for the Winter Triangle: Brilliant Sirius in WSW with Procyon 26 degrees above, and Betelgeuse to their right, in the west. For the rest of April, Comet H-B shifts its position by one degree daily. In a few weeks, Sirius, Betelgeuse, and the comet will all sink into the twilight glow for observers at mid-northern latitudes. Sunday, April 27 At nightfall, locate bright Mars high in SSE to S. Note Regulus in Leo 17 degrees to Mars' upper right, and Spica in Virgo 37 degrees to Mars' lower left. Tonight Mars ends its apparent retrograde (backward or westward) motion and begins to approach Spica, which it will pass on August 3. Mars goes very slowly at first. If your sky is dark enough, you can see the 4th-mag. star Sigma in the hind leg of Leo just 2 degrees to Mars' lower left. Mars will pass very near that star on May 15, just as the Moon comes through next time around. Monday, April 28 At nightfall locate zero-magnitude Capella, brightest star in WNW to NW, and the 2nd-mag. star Elnath (northern horn of Taurus) 18 degrees to Capella's lower left. Comet Hale-Bopp is low in WNW, 21 deg. lower left of Capella and 12 deg. to lower right of Elnath. H-B should now appear as a fuzzy "star' of between zero and first magnitude. Tuesday, April 29 On Wednesday one to two hours before sunrise, the Moon is low in SE with bright Jupiter 6 or 7 degrees to its lower left. Note the Moon is slightly less than half full. It has just passed Last Quarter phase, when it was 90 degrees or one-quarter circle west of the Sun. These are fine mornings for using binoculars or a small telescope to view the spectacular detail in the lunar landscape near the Moon's terminator (day-night boundary). While you're out before dawn, enjoy the morning choruses of bird songs. Wednesday, April 30 At nightfall, Comet Hale-Bopp is low in WNW, 21 degrees lower left of the bright "Mother Goat" star Capella and 10 degrees lower right of the northern horn of Taurus. One to two hours before sunup on Thursday, face SE to see bright Jupiter 9 degrees to the right of a fat crescent Moon, about one-third full. ********** end of Skywatcher's Diary for April 1997 **********