Abrams Planetarium Skywatcher's Diary
July 1998
To the reader:
The Skywatcher's Diary for July 1998 has been prepared
by Robert C. Victor. Credit to the author and to Abrams Planetarium, Department
of Physics and Astronomy at Michigan State
University, and mention of our Sky Calendar, would be appreciated.
A sample recent issue of the Sky Calendar is available
over the Internet. It can be viewed via a World-Wide Web browser at
http://www.pa.msu.edu/abrams/SkyCalendar/Index-t.html
If you would like a printed sample of the July issue, send a long,
self-addressed stamped envelope to:
July 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 with a World-Wide Web browser at:
http://www.pa.msu.edu/abrams/SWD/Diary.html
The Skywatcher's Diary is also available via anonymous ftp at:
ftp://www.pa.msu.edu/pub/swd/
Here are the bright planets, in the order they appear during July nights. Mercury, at dusk, is best in first half of month, because it's brightest (mag. -0.2) at start of July, and highest (6 degrees up in WNW in mid- twilight for lat. 40 degrees N) on July 7. Mercury fades to +0.5 by July 16 and +1.0 by July 24, when it's less than 2 degrees up in mid-twilight. Approaching Regulus most of month, Mercury pauses 3.9 degrees below star July 26, then pulls away. That event is a "quasi-conjunction", because Mercury does not pass the star. Mercury fades to match Regulus (+1.3) on July 28, but then only observers in S states will see it in bright twilight 4 degrees below Regulus. Bright Jupiter rises about 3 degrees S of due E, within 4 hours after sunset on July 1, and just over 2 hours after sunset on July 31. Saturn rises about 15 degrees N of E about 1-1/2 hours later than Jupiter. For rest of night, Saturn trails Jupiter across the sky, 34 to 36 degrees E of the giant planet and three magnitudes fainter. At dawn, both Jupiter and Saturn are well up, Jupiter drifting through SSE and S toward SSW as month progresses, while Saturn begins in ESE and ascends high into SE. Telescopically, Saturn's rings are tipped more than 16 degrees from edge-on, our best view since 1992. Venus rises farthest N of E this month, about 2 hours before sunrise, or first light of dawn. Venus passes 4 degrees N of 1st- mag Aldebaran July 2. Mars is now just emerging from solar glare, to lower left of Venus. On what date will you first spot Mars? Watch the gap between Venus and Mars narrow to 8 degrees on July 21, 5 degrees on July 27, and 2.7 degrees July 31.
The Moon passes all the bright planets this month; see July 13-16, 19-21, 24-25, below.
Skywatcher's Diary: July 1998
Wednesday, July 1
This afternoon, the First Quarter Moon is 90 degrees, or one-quarter circle, east of the Sun. Note the western half of the Moon's disk, the side toward the Sun, is illuminated. An hour after sunset, Moon is in SW, with the first-magnitude star Spica, spike of wheat in the hand of Virgo, about 11 degrees to Moon's lower left. For a few days, the Moon is ideal for observation with binoculars and small telescopes, displaying wonderful surface detail near the terminator, or day-night boundary.
Brilliant Venus gleams low in ENE an hour before sunrise all month. On Thursday, first-magnitude Aldebaran, eye of Taurus the Bull, is just 4 degrees to Venus' lower right.
Thursday, July 2
The waxing gibbous Moon is in the southwestern sky as darkness falls. Look for Spica 5 or 6 degrees below the Moon, and bright golden Arcturus about 27 degrees above. These two bright stars can be found with the Big Dipper's handle. Find the Big Dipper in the NW, then "Follow the arc to Arcturus, and drive a spike to Spica."
Friday, July 3
At dusk, look for Mercury very low in WNW, with Regulus in W, 25 degrees to planet's upper left. Watch the gap between them close in next three weeks. An hour after sunset tonight Moon is in SSW, with Spica about 15 degrees to its lower right.
Saturday, July 4
An hour after sunset, Moon is in southern sky, with Antares, heart of Scorpius the Scorpion, 22 degrees to its lower left. Look for a pair of 3rd-magnitude stars 9 degrees apart in Libra: Zubeneschamali, 4 degrees above the Moon, and Zubenelgenubi, about 6 degrees to Moon's lower right. These names mean "Northern Claw" and "Southern Claw", referring to the fact that these stars marked the claws of an early version of the Scorpion larger than the present day constellation. The Southern Claw star, Alpha in Libra, is a fine double star for binoculars.
Sunday, July 5
An hour after sunset, the Moon is just east of due south, with the first- magnitude reddish supergiant star Antares, heart of Scorpius, 12 degrees lower left. Some 3-1/2 to 10 degrees below Moon, look for a slightly bent vertical line of three stars, marking Scorpion's head.
Monday, July 6
An hour after sunset, Moon is in SSE, with Antares twinkling10 degrees to its lower right.
Tuesday, July 7
Tonight at dusk, Mercury is very low in WNW, 19 degrees lower right of Regulus. Evening by evening, Mercury will gradually get lower and fade, so if you haven't spotted it yet during this apparition, look soon! The next good evening appearance of Mercury will come in February- March 1999.
Wednesday, July 8
Shortly before sunset, the Sun and the nearly Full Moon can be seen simultaneously in almost opposite directions. Will it be possible again on Thursday evening?
An hour before sunup on Thursday, brilliant Venus is low in ENE, with reddish Aldebaran, eye of Taurus the Bull, 9 degrees upper right. Using binoculars, try for Mars very near horizon, 14 degrees to Venus' lower left.
Thursday, July 9
The Moon is Full today at 12:10 p.m. EDT. In northern U.S. today, from places with unobstructed views toward WNW and ESE, it may be possible to observe the Moon rising just as the sun sets. Up all night, the Moon will remain visible until it sets about an hour after sunrise on Friday morning.
Friday, July 10
At dusk, look low in W to WNW for Mercury 15 degrees lower right of Regulus. From lower Michigan 45 minutes after sunset, the disk of the Moon has just risen in ESE.
Milky Way Legacy continues 8:00 p.m. tonight at Abrams Planetarium. Tour our amazing home galaxy with noted author Ken Croswell and emerge with a clearer view of our home in space. Find out some of the ways the Milky Way is very special, and how, unlike most galaxies, it is equipped to create the variety of ingredients needed for life. Showtimes are Fridays and Saturdays at 8 p.m., Sundays at 4 p.m., through August 2.
Saturday, July 11 >From northern U.S., for one more night, the Moon comes up before nightfall. From lower Michigan, tonight's Moon comes up 20 degrees S of E, within 1-1/2 hours after sunset.
Sunday, July 12
From southern Michigan and places farther south, the Moon rises over two hours after sunset. Before the Moon rises and brightens the sky, look for the Milky Way passing through the Summer Triangle in the east.
Our family show, WSKY ... Radio Station of the Stars, is presented Sundays, 2:30 p.m. at Abrams Planetarium, through August 2.
Monday, July 13
Tonight about 3-1/2 hours after sunset, look for Jupiter low in eastern sky about 8 degrees to lower left of the waning gibbous Moon. By an hour before sunup on Tuesday, they're high in SSE to S, and 6 degrees apart.
Tuesday, July 14
Tonight 3-1/2 hours after sunset, Moon has just risen just south of due east, and bright Jupiter is 6 degrees to its upper right. By an hour before sunup on Wednesday, they've widened to 8 degrees apart, high in SSE.
Wednesday, July 15
Five hours after sunset tonight, look low in E for the Moon, with Saturn 14 degrees to its lower left. Bright Jupiter is in ESE, 21 degrees to Moon's upper right. By an hour before sunup on Thursday, Moon is well up in SE, with Saturn some 12 degrees to its left, and bright Jupiter not quite twice as far to Moon's upper right. The Moon is approaching Last Quarter phase, and will appear half full in Thursday's daytime sky, staying about90 degrees or one-quarter of a circle west of the Sun until the Moon sets, shortly after midday.
Thursday, July 16
Five hours after sunset tonight, a fat crescent Moon is low in E, and Saturn is within 3 degrees to its upper left. Bright Jupiter is in ESE, 35 degrees to upper right of the Moon-Saturn pair. By an hour before sunup, the Moon-Saturn pair, still close, is well up in ESE.
Friday, July 17
Now that the Moon rises late, evenings are dark for Milky Way viewing. Two hours after sunset, follow the Milky Way from the Teapot of Sagittarius in SE, through the Summer Triangle high in E, and Cassiopeia low in NE.
The beautiful constellation Scorpius is then near its best position for observation. First-magnitude reddish Antares, the heart of the Scorpion, passes due south around then, while 1.6-mag. Shaula, at the end of the Scorpion's tail, is 17 degrees to lower left. Note Shaula has a naked-eye companion star 0.6 degree to its right and a magnitude fainter; the two stars give the appearance of two "cat's eyes". Binoculars reveal many treasures in this constellation. A few examples: the star cluster M7 (Messier 7) is 5 degrees upper left of Shaula, and another cluster, M6, lies 4 degrees upper right of M7. Upsilon, a fine double star for binoculars, is 8 degrees right of Shaula, and another double, Zeta, lies 4 degrees below Upsilon. For lists of additional objects for binoculars, visit the Astronomical League Observing Clubs at http://www.mcs.net/~bstevens/al/obsclub.html and view the items Messier Club, Binocular Messier Club and Deep Sky Binocular Club.
Saturday, July 18
An hour before sunrise on Sunday, the zodiac is well marked by six bright objects: four planets, the Moon, and one star. In order from west to east, they are: Bright Jupiter, high in the southern sky; Saturn, 35 degrees to Jupiter's left; the Moon, in east about 30 degrees lower left of Saturn; Aldebaran, eye of Taurus, about 6 degrees lower left of Moon; brilliant Venus, low in ENE, 20 degrees lower left of Aldebaran; and finally Mars, 9 degrees lower left of Venus.
Sunday, July 19
An hour before sunup on Monday, face the eastern sky to see a crescent Moon with brilliant Venus 14 degrees to its lower left. Aldebaran, eye of Taurus, is 8 degrees to Moon's upper right. Using binoculars, watch for the rising of Betelgeuse, shoulder of Orion, 15 degrees below the Moon and the same distance lower right of Venus.
Monday, July 20
On Tuesday an hour before sunup, don't miss this beautiful sight low in ENE: A slender waning crescent Moon, with brilliant Venus 4 or 5 degrees to its upper left. Faint Mars is 8 degrees to Venus' lower left, and Betelgeuse is 11 degrees lower right of the Moon.
Tuesday, July 21
Here are some challenging sights for binoculars in evening and morning twilight overnight: First, this evening, about 45 minutes after sunset, look very low, between W and WNW, for Mercury 5 degrees lower right of Regulus. About an hour before sunup on Wednesday, locate Venus low in ENE with Mars 7-1/2 degrees to its lower left. Wait another 20 minutes, and watch for the slender crescent old Moon rising 7 degrees below Mars and 13 degrees lower left of Venus.
Wednesday, July 22
Near latitude 39 degrees north, from Delaware to northern California, the bright blue-white star Vega passes directly overhead, about 3-1/4 hours after sunset tonight and about four minutes earlier each night.
Thursday, July 23
The Moon is New today at 9:44 a.m. EDT, so we have a few more evenings to enjoy superb views of the Milky Way after nightfall. Two hours after sunset, the equatorial plane of our Galaxy arches high across the eastern sky. Follow the course of the Milky Way from the "W" of Cassiopeia low in NNE, through the Summer Triangle high in E, past the Teapot of Sagittarius low in SSE, to the tail of Scorpius. There's an especially bright patch of Milky Way within the Summer Triangle, along the Northern Cross. The view of this "Cygnus Star Cloud" through binoculars is wonderful!
Friday, July 24
Using binoculars 15 minutes after sunset, try for the very slender young Moon very low, about 15 degrees north of due west. As the Moon sets, try for Mercury about 7 degrees to its upper left, and Regulus just over 4 degrees upper left of Mercury.
Saturday, July 25
Although it is very low, the thin crescent Moon is easy to see 40 minutes after sunset, provided the sky is clear and you have an unobstructed view. Look about 8 degrees north of due west. Binoculars may show Regulus 2 or 3 degrees to the Moon's right, and Mercury 4 degrees lower right of Regulus.
Sunday, July 26
The crescent Moon is low, nearly due west 40 minutes after sunset. Using binoculars, try for Regulus 15 degrees to Moon's lower right, and Mercury 4 degrees below Regulus.
Low in ENE an hour before sunup on Monday, faint Mars is now just 5 degrees lower left of brilliant Venus. The gap between them is narrowing daily, and they'll be within one degree apart on Aug. 4 and 5.
Monday, July 27
An hour before sunrise on Tuesday, Pollux and Castor, heads of the Gemini twins, are very low in NE, 14 degrees left of Venus. The two stars are 4-1/2 degrees apart, with Castor above Pollux. From Tuesday through Aug. 12, Venus and Mars stay within 4-1/2 degrees apart, and they will be within one degree on Aug. 4 and 5. Watch for changes in the arrangement of the foursome as Venus and Mars move against background of Gemini.
Tuesday, July 28
An hour after sunset, the waxing crescent Moon is in WSW, with Spica 15 degrees to its left. Golden Arcturus, the brightest star in evening sky, is 32 degrees above the Moon.
Orion is back! On Wednesday an hour before sunup, find brilliant Venus low in ENE, and look in E for Betelgeuse, Orion's shoulder, 20 degrees to Venus' right. Some 19 degrees right of Betelgeuse (and a few degrees lower from N states) is Rigel, the Hunter's foot. Look midway between Betelgeuse and Rigel for a vertical line of three stars, Orion's belt.
Wednesday, July 29
As sky darkens, notice Spica 6 degrees to Moon's lower left.
Thursday, July 30
Moon, approaching First Quarter phase and nearly half full, is in SW at dusk. Note Spica in Virgo, 10 or 11 degrees to Moon's lower right.
Friday, July 31
The Moon has passed First Quarter phase and is now slightly more than 90 degrees from the setting Sun and appears just over half full. As the sky darkens, look 4 degrees below the Moon for the 3rd-magnitude star Alpha in Libra (Zubenelgenubi, the Scorpion's southern claw). Binoculars reveal it as a double star, whose components are 4 arcminutes apart, magnitudes 3 and 5.
This is the final weekend for showings of Milky Way Legacy and WSKY ... Radio Station of the Stars, at Abrams Planetarium. The Planetarium will be closed August 2 through Labor Day. Programs will resume after mid-September, with one or two weekends of Autumn Skies. For program information, call (517) 355-4672.
This Friday and Saturday, MSU Observatory will be open for public viewing from 9:00 until 11:00 p.m. if skies are clear.
