Abrams Planetarium

SKYWATCHER'S DIARY: July 1997

To the reader

The Skywatcher's Diary for July 1997 has been prepared by Robert C. Victor. Sometimes you can see next month's in advance by looking in our archives. 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 issue of Sky Calendar from a previous month is available over the Internet. It can be viewed via a World-Wide Web browser such as Netscape or Internet Explorer, directly at URL:

http://www.pa.msu.edu/abrams/apr97skycal.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 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

ftp://www.pa.msu.edu/pub/swd/

July Planetary Highlights:

Evening Planets: Venus is very low in WNW to W at dusk. Near mag. -4, it's the brightest "star" in the night sky, but it sets in twilight within 1-1/2 hours after sunset (from latitude of lower Michigan) in July, and won't be seen in a fully dark sky until September. Mercury is visible to lower right of Venus after first week of July and forms beautiful groupings with Venus and Regulus which can be enjoyed with binoculars. In the week of July 6-12, Moon introduces two planets and three zodiacal stars to casual skywatchers with a young crescent Moon near Venus July 6 and near Regulus the next two evenings; then a fat crescent Moon passes very close to Mars on July 11, and a half Moon is seen near Spica the next evening. Striking gatherings for binoculars, with two or three bright objects in the same field, occur nightly in the latter half of July. The closest pairings occur as Venus overtakes Regulus on July 22 and as Mercury passes the same star four nights later. Mars, still rather bright at mag +0.6 to +0.8, is in SW to WSW at dusk. Look 18 degrees lower right of first-magnitude Spica on July 1, closing to 6 degrees right of Spica by July 24, and 2.4 degrees upper right of that star on July 31. On August 3 Mars will pass 1.6 degrees north (upper right) of Spica.

Late evening until dawn: Jupiter, as seen from lower Michigan's latitude, rises in ESE two hours after sunset in early July and reaches south some 1-1/2 hours before sunup. At end of July Jupiter rises within half an hour after sunset and is in SW at dawn. Once Venus has set and Jupiter has risen, Jupiter at mag -2.7 to -2.8 is brightest "star" in sky until dawn. Waning gibbous Moon is found near Jupiter on nights of July 20 and 21.

Saturn, of mag +0.7 to +0.5, rises just N of E about 2-1/2 hours after Jupiter (seen from latitude of lower Michigan; south of there the waiting time is longer). At dawn Saturn is in ESE to SSE, getting higher as month progresses. A waning gibbous Moon, just over half full, is near Saturn on mornings of July 25 and 26. Saturn's rings have opened nicely since they were edgewise and invisible two years ago; see July 24.

The Moon covers Aldebaran on the morning of July 29; see July 27 and 28 for details.

Tuesday, July 1

An hour before sunrise on Wednesday, the old crescent Moon is very low in ENE, with first-magnitude Aldebaran close to Moon's upper right; Aldebaran is 2 degrees from Moon's dimly earthlit edge (as seen from Boston) to 4 degrees (as seen from San Diego).

Wednesday, July 2

Using binoculars half an hour before sunrise on Thursday, scan the ENE horizon to try for the old crescent Moon, just risen. Within the U.S., the sighting will be highest and easiest from southeastern states, and most difficult from the Pacific Northwest.

Thursday, July 3

Two hours after sunset, the beautiful constellation Scorpius nears 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.

Friday, July 4

The Moon is New today at 2:40 p.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!

Saturday, July 5

The young crescent Moon will be visible to the unaided eye tonight across southern U.S., westward to southern California and Hawaii. Starting 15 minutes after sunset, look low, between W and WNW, about 12 degrees lower right of Venus. As the sky darkens and the Moon sets, watch for Mercury 7 degrees to Moon's upper right. From northern states, the Moon sets earlier in a brighter sky, and seeing the crescent will require binoculars.

Sunday, July 6

Tonight, the young Moon should be easy for all of the U.S. except Alaska. Forty minutes after sunset, the crescent is very low, about 15 degrees north of due west. Bright Venus is within 6 degrees to its upper right. Binoculars will help spot Mercury barely above horizon 12 degrees lower right of Venus. From southern states, Mercury is easy for unaided eye.

Monday, July 7

Half an hour after sunset, face west to see the crescent Moon with Venus about 12 degrees to its lower right. As twilight deepens in the next 15 to 30 minutes, try for Mercury 12 degrees to Venus' lower right, and Regulus about 7 degrees to Moon's upper left.

Tuesday, July 8

An hour after sunset these evenings, the most prominent objects are: Moon; Venus very low in WNW; Arcturus high in SW; Vega high in E; Altair in E to ESE, 34 degrees lower right of Vega; and Mars in SW to WSW, 34 degrees lower right of Arcturus.

Wednesday, July 9

At dusk an arc nearly a quarter of the way around the zodiac is well marked by three planets, the Moon, and two stars. In order from the WNW horizon to the upper left tonight and Thursday are: Mercury; Venus (very bright); the star Regulus, marking the heart of Leo; the Moon; Mars; and Spica, marking the spike of wheat in the hand of Virgo.

Thursday, July 10

An hour after sunset, note Moon in WSW, Venus very low in WNW, and Mars and Spica 12 degrees and 25 degrees to Moon's upper left. Recall that the Moon passed near Venus on Sunday. Try to predict the Moon's location for Friday and Saturday evenings, then check your predictions by observation.

Friday, July 11

The reddish "star" closely lower left of the south cusp or lower point of the crescent Moon at dusk is the planet Mars. Check their positions every half hour and watch for changes.

MSU Observatory will be open for viewing tonight and Saturday, 9:15- 11:00 p.m., if skies are clear, after 8 p.m. showings of From Stardust to Life at Abrams Planetarium.

Saturday, July 12

Today the Moon passes First Quarter phase, so it is 90 degrees or one- quarter circle east of the Sun in afternoon and evening. Face the setting Sun today, and the Moon will be over your left shoulder with its left half illuminated. Especially when Moon is about half full, binoculars show spectacular details near the Moon's terminator. The bright star to Moon's lower left at dusk is Spica. Remember this star's name and how to find it by saying, "Follow the arc (of the Big Dipper's handle) to Arcturus and drive a spike to Spica."

Sunday, July 13

At dusk, locate the star Spica about 12 degrees to Moon's lower right and 12 degrees left of Mars. Bright Arcturus stands 33 degrees above Mars and Spica. Three weeks from tonight, Mars will pass less than 2 degrees from Spica. Be sure to look each clear night until then!

Monday, July 14

Two hours after sunset, cover Moon with your left hand, and look for two 3rd-magnitude stars within 4 or 5 degrees of the Moon. To the lower right of Moon is Alpha Librae or Zubenelgenubi, the northern claw. Above Moon is Beta Librae, or Zubeneschamali, the southern claw. These stars mark the claws of an earlier, large version of the Scorpion. Antares, the Scorpion's heart, is 23 degrees to Moon's lower left, and the head of Scorpius is a nearly vertical "fence" of three stars between Antares and the Moon.

Tuesday, July 15

An hour after sunset, the red supergiant star Antares, heart of Scorpius, lies 12 degrees to Moon's lower left. The head of the Scorpion consist of three stars of 2nd and 3rd magnitude in a nearly vertical line, 4 to 10 degrees below the Moon.

Wednesday, July 16

Find Moon just east of due south an hour after sunset, with Antares 10 degrees lower left.

Thursday, July 17

About 45 minutes after sunset, brilliant Venus, very low in W to WNW, is flanked by two lesser gems, each just over 6 degrees away. As twilight dims, binoculars help spot Mercury to lower right, Regulus to upper left; keep watch each clear evening as group becomes more and more compact nightly!

Friday, July 18

Two hours after sunset, find the Moon in SSE with bright Altair about 30 degrees to its upper left. The eight bright stars of the Teapot of Sagittarius, even though of 2nd and 3rd magnitude, are almost lost in the lunar glare 7 to 17 degrees to Moon's lower right.

Saturday, July 19

Tonight's Full Thunder Moon (as named by Algonquians) is above the horizon all night. You can see the Sun and Moon simultaneously in nearly opposite directions 15 minutes before sunset tonight and 15 minutes after sunrise on Sunday. In the course of the night, bright Jupiter follows the Moon by about 1-1/2 hours.

Sunday, July 20

For most of U.S. tonight, the Moon rises in ESE 15 to 30 minutes after sunset. About one to 1-1/2 hours after sunset, watch for bright Jupiter rising 8 degrees to Moon's lower left. By dawn on Monday, they're in the SW, about 5 degrees apart.

Monday, July 21

Tonight the waning gibbous Moon rises in E to ESE just over an hour after sunset from southern Michigan. (Its appearance is later after sunset if you're farther south, sooner if farther north.) As the Moon rises, look for Jupiter 8 degrees to its upper right.

Tuesday, July 22

At dusk find bright Venus very low in W to WNW. Binoculars help you find Regulus within 1.2 degrees lower left of Venus, and Mercury 5 degrees to their lower right. Reddish Mars and blue-white Spica are 7 degrees apart in SW. Can you spot bright Jupiter rising in ESE before Venus sets in WNW? You'll need unobstructed views.

Wednesday, July 23

At dusk look between W and WNW to find bright Venus with Mercury within 5 degrees to its lower right. Mercury is at its highest now, but is only 4 degrees up in mid-twilight from lat. 40 deg N. Binoculars show Regulus within 1.5 degrees below Venus. Look nightly!

Thursday, July 24

At dusk find Venus very low in W to WNW with Mercury 4.6 degrees to its lower right; fainter Regulus is midway between them. In the SW, Mars and Spica are now 6 degrees apart, and will close to within 2 degrees in next 10 days. Can you spot Jupiter rising in ESE before either Mercury or Venus sets?

An hour before sunrise on Friday, Jupiter is in SW. Moon will then be in SSE, with Saturn about 6 degrees to its left. Saturn's rings are now tipped 11.7 degrees from edge-on, our greatest viewing angle during 1997.

Friday, July 25

This evening is the most compact arrangement of Venus, Mercury, and Regulus. Locate Venus very low, N of west at dusk. Regulus and Mercury are now 1 degree apart, and are respectively 3.5 degrees and 4.5 degrees to lower right of Venus. Use binoculars!

An hour before sunup on Saturday, Moon is in SE with Saturn 8 degrees upper right. Seen through binoculars, the Moon shows wonderful detail, especially near the terminator (day-night boundary). Follow the Moon past sunrise until early afternoon on Saturday. It's near Last Quarter phase, 90 degrees west of the Sun, and appears half full.

Saturday, July 26

Find bright Venus very low, north of due west at dusk. Using binoculars, locate Mercury 4.5 degrees to Venus' lower right tonight through Monday. Tonight Regulus is 0.6 degree upper right of Mercury, but the star sinks lower nightly. In SW, Mars and Spica are now within 5 degrees apart.

Sunday, July 27

Two or three hours before sunrise on Monday, the waning crescent Moon, one-third full, is low in east. The Pleiades or Seven Sisters star cluster is beautiful in binoculars 10 degrees to Moon's upper left. The first-magnitude star Aldebaran, eye of Taurus, the Bull, is 14 degrees to Moon's lower left.

The Moon will occult, or cover, Aldebaran on Tuesday morning. The event can be seen in U.S. and Canada south of a line crossing central California, Nevada, Utah, Wyoming, the Dakotas, northern Minnesota, western Ontario, and James Bay. The far West sees the occultation in predawn darkness, the East in twilight or daylight. Additional details will be given on Monday. For more information, see pp. 90-92 of the January 1997 issue of Sky & Telescope, pp. 93-96 of the July issue, and the IOTA Webpage at http://www.sky.net/~robinson/iotandx.htm

Monday, July 28

If you're in a good location on Tuesday morning, July 29, don't miss the occultation of Aldebaran! The event begins as the leading lower bright edge of the Moon covers the star; the instant of disappearance is best observed with a telescope. From Arizona, most of Utah, and roughly the southern halves of California and Nevada, the star is then very low in ENE soon after moonrise. From Denver the star is already 15 deg up as it is covered. Along a line from Duluth through Detroit, Cleveland, Pittsburgh, and Norfolk, VA, the star is 28 to 36 deg up in E as it disappears behind Moon's bright edge. But along that line it's already midtwilight, with Sun 9 degrees below horizon, less than an hour before sunup. From northeastern NY State to Rhode Island, star's disappearance takes place at sunrise.

Striking views may be had from western U.S. where the sky is dark as Aldebaran emerges from behind the Moon's dimly earthlit upper limb. Even as far east as Omaha, Kansas City, and Mobile this event takes place at nautical twilight, when the Sun is 12 degrees down and the sky is dark enough to allow seeing Aldebaran's emergence with unaided eye (although the view through binoculars or a telescope is best). Farther east, from Duluth, Atlanta, and Jacksonville, emergence takes place in the brighter skies of civil twilight with the Sun 6 degrees down, so optical aid will be required. From Michigan, Ohio, the Virginias, and the Carolinas, Aldebaran emerges around sunrise.

Here are times of Aldebaran's disappearance and reappearance for selected cities: Los Angeles 2:22-2:52 a.m. PDT; Tucson 2:13-2:55 a.m. MST; Albuquerque 3:17-3:58 a.m. MDT; Denver 3:30-3:59 a.m. MDT; Austin 4:04-5:02 a.m. CDT; Kansas City 4:23-5:11 a.m. CDT; Chicago 4:30-5:20 a.m. CDT; Miami 5:03-6:12 a.m. EDT; Atlanta 5:12-6:19 a.m. EDT; Washington DC 5:26-6:34 a.m. EDT; Pittsburgh 5:28-6:31 a.m. EDT; Detroit 5:32-6:27 a.m. EDT; East Lansing 5:33- 6:25 a.m. EDT; Toronto 5:37-6:33 a.m. EDT.

A spectacular grazing occultation may be seen within a mile or two of the northern limit of this event, which passes through central California, Nevada, Utah (crossing Salt Lake City area), Wyoming, Dakotas, northern Minnesota, western Ontario, and James Bay. If you're within this very narrow zone, Aldebaran may wink on and off several times as it alternately hides behind lunar mountains and reappears within valleys near the Moon's north pole.

For more information on the Aldebaran occultation or the graze, visit the IOTA Webpage at: http://www.sky.net/~robinson/iotandx.htm

Tuesday, July 29

If you have a pair of binoculars, you can do an easy "star hop" from Jupiter to Uranus. Two to three hours after sunset, locate bright Jupiter in SE. Nearly 5-1/2 degrees to Jupiter's lower left is 3rd-magnitude Deneb Algedi or Delta Capricorni, brightest star in constellation of the Sea-goat. Is field of view of your binoculars wide enough to include both Jupiter and Delta? (When "star hopping", it's handy to know angular width of your binoculars' field.) Next, look just over 4-1/2 degrees to Jupiter's upper right for 4th-mag Theta. A line from Jupiter to Theta extended 2-3/4 degrees straight beyond Theta brings you to 6th-mag star, 19 Capricorni. Another 3-1/2 degrees upper right of 19 brings you to 5th-mag Upsilon Capricorni. Tonight Uranus is 1.3 degrees lower right of Upsilon Cap. At mag 5.7, the planet is noticeably fainter than Upsilon and a little brighter than 19 Cap. As a check, there's a compact triangle of 5th and 6th mag stars, Omicron, Rho, and Pi Capricorni, about 2 to 2-1/2 degrees upper right of Uranus. For a finder chart, see box for July 29 on our Sky Calendar, or a more detailed chart in May Sky & Telescope. In coming weeks, watch for changes in positions of Jupiter and Uranus. Both planets now appear to retrograde, or move west against the stars, because faster-moving Earth is overtaking them.

Orion is back! On Wednesday one and a quarter hours before sunup, face east to see the crescent Moon, with Aldebaran, eye of Taurus, 12 degrees upper right, and Betelgeuse, Orion's shoulder, 12 degrees to lower right. Some 19 degrees right of Betelgeuse (and a few degrees lower from northern states) is Rigel, the Hunter's foot. Look about midway between Betelgeuse and Rigel for a vertical line of three stars, Orion's belt.

Wednesday, July 30

On Thursday one and a quarter hours before sunup, look low, north of east, for a beautiful crescent Moon with earthshine filling out the darker portion of the disk. Orion's two bright stars, Betelgeuse and Rigel, are 12 and 30 degrees to the Moon's right. Some 22 degrees to Moon's left are the Gemini twins, Castor 4-1/2 degrees above Pollux.

Thursday, July 31

About 45 minutes after sunset, find brilliant Venus very low in W. Using binoculars as twilight deepens, look for Mercury 5 degrees to its lower right. (Viewers in southern states can also spot Regulus 6 degrees lower right of Mercury.) In the southwest, find Mars with Spica 2.4 degrees lower left; watch them nightly! Bright Jupiter has just risen in ESE.

Last chance for Moon! An hour before sunup on Friday, the thin old crescent is very low in ENE. Pollux, the brighter Gemini twin, is 13 degrees to Moon's upper left.

Friday, August 1

Look low SW at dusk nightly through Tuesday to find Mars within 2 degrees of Spica.

Saturday, August 2

New Moon Sunday, 4:14 a.m. EDT; first easy view for northern states is Tuesday at dusk.

Sunday, August 3

Mars is 1.6 degrees upper right of Spica; they're closest tonight! Look low SW at dusk.

Monday, August 4

Using binoculars 15 minutes after sunset, look very low 10 degrees north of due west for the thin crescent young Moon. It is within 15 degrees lower right of Venus. After the Moon sets, try for Mercury 6 degrees to Venus' lower right. As the sky darkens, Mars is in WSW 1.7 degrees directly above Spica tonight, while bright Jupiter has risen in ESE.

Tuesday, August 5

About 45 minutes after sunset, the crescent Moon is very low in W, with Venus 4 degrees upper left, and Mercury 2 degrees lower right. (From the West Coast, Moon is about 3 degrees from each.) Binoculars may be needed to see Mercury. In WSW, Mars is 2 degrees upper left of Spica. Jupiter is very low in ESE.

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