Abrams Planetarium

SKYWATCHER'S DIARY: September 1995

To the reader

The Skywatcher's Diary for September 1995 has been prepared by David Nette and Robert 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 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

TO USERS: The *Skywatcher's Diary* for September 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. Michigan

This month's most striking sights include the moon passing near planets and bright stars, on the evenings of September 1, 2, 8, 9, 25, 27-29, and the mornings of September 9, 15, 17, 19, 22. Morning events are mentioned in Skywatcher's Diary one day prior to the event. *For observers with telescopes*, an arrangement of Jupiter's satellites is described under Sept. 1, and Jupiter's close brush past a star is mentioned under Sept. 24. *Saturn's rings* are visible again, but are unusually close to edgewise; the location and telescopic appearance of the planet is described under Sept. 1, 7-10, 14, 29.


Friday, September 1

An hour after sunset the moon, approaching First Quarter, is in SSW. Bright Jupiter is 3 degrees to moon's lower left. The reddish twinkling star 6 degrees lower left of Jupiter is Antares, the heart of the Scorpion. Binoculars give spectacular views of lunar surface features and show Ganymede and Callisto, Jupiter's two largest satellites, just west (lower right) of the planet tonight.

At 9:01 p.m. EDT tonight, the Russian space station Mir makes its last nighttime pass through Michigan skies for several weeks. At that time from the Lansing area, Mir will appear as a bright star 57 degrees up in SW, moving from right to left. [Updates will be available on our recorded sky events line at (517) 332-STAR.]

Within two hours after sunset Saturn will have risen 15 degrees up in ESE, the same altitude as Jupiter then sinking in SW. Using a telescope, can you detect Saturn's ring system? Since it's now tipped only about 3/4 of a degree from edgewise, it gives the appearance of a line of light piercing the planet -- Saturn kabob!

For the next week until the moon is full on September 8, you can watch the moon, near Jupiter tonight, move closer to Saturn on each successive night.

Saturday, September 2

An hour after sunset the waxing gibbous moon is in the SSW. Bright yellowish Jupiter and twinkling reddish Antares, the heart of the Scorpion, shine 6 degrees apart and 12 degrees to moon's lower right.

Sunday, September 3

The moon is in S at dusk with bright Jupiter 26 degrees to its lower right. Antares in Scorpius is 6 degrees lower left of Jupiter.

Monday, September 4

The gibbous moon is in SSE at dusk.As the sky darkens, the Teapot of Sagittarius can be seen to moon's lower right. The moon will occult, or cover the 4th-magnitude star Rho Sagittarii tonight throughout the U.S. except for the Southeast. Use a telescope to see the star disappear at the moon's invisible dark edge. Times for selected cities: Los Angeles 8:37 p.m. PDT; Denver 10:05 p.m. MDT; Chicago 11:37 p.m. CDT; E. Lansing MI 12:41 a.m. EDT; Washington DC 1:05 a.m. EDT. For other cities and a map, see Jan. 1995 Sky & Telescope, pp. 80-81.

Tuesday, September 5

An hour after sundown the waxing gibbous moon is in SSE. The moon will occult the 3rd-magnitude star Beta Capricorni tonight in all of U.S. except for the Northwest. Use a telescope to see the star disappear at the moon's invisible dark edge. Times for selected cities: LosAngeles 9:10 PDT; Denver 10:41 p.m. MDT; Chicago 11:58 p.m. CDT; E. Lansing MI 1:01 a.m. EDT; Washington DC 1:06 a.m. EDT.

Wednesday, September 6

Look early, starting half an hour after sundown, for elusive Mercury, very low, about 10 degrees S of due west. Although Mercury reaches its greatest angular distance 27 degrees from Sun this week, it remains very low in twilight and very difficult to see from all except southern states; use binoculars. A little higher in WSW are reddish Mars and Spica, 6 degrees apart and widening.

Thursday, September 7

An hour after sunset face ESE to see the nearly full moon with Saturn rising 22 degrees to its lower left. Later in the evening, when Saturn has risen much higher, examine it through a telescope. Saturn's rings appear narrow as their illuminated N face is tipped only slightly into our view. Take advantage of the opportunity to observe as many of Saturn's satellites as you can in the next few months, while the rings are less bright than usual. Saturn's brightest moon, Titan, is easily visible with a modest telescope. In its 16-day orbit, Titan appears farthest W of Saturn on Sept. 11 and 27, and farthest E on Sept. 19.

An hour before sunup on Friday, the moon is about to set just S of west, with Saturn 18 degrees to its upper left.

Friday, September 8

The Full Moon rests on the horizon, 5 degrees S of due east, 20-25 minutes before sunset. An hour after sunset this Harvest Moon is low in ESE with Saturn 8 degrees to its lower left. From now until Tuesday, from northern U.S., the moon rises within just 35 minutes later on each successive night. At dawn on Saturday, the moon is low in WSW with Saturn 6 degrees to its left.

Saturday, September 9

The moon rises a degree or two N of due east within 10 minutes after sunset. An hour later look for yellowish Saturn, 8 degrees to the moon's right. An hour before sunup Sunday the moon is in the WSW with Saturn 12 degrees below.

Tonight through Monday, Harvest moonrise watches will be held atop the parking ramp immediately behind Abrams Planetarium, at the following dates and times, as sky conditions permit: Sat. Sept. 9, from 8:00 p.m. until 9:30 p.m. Sun. Sept. 10, from 8:30 p.m. until 9:30 p.m. Mon. Sept. 11, from 9:00 p.m. until 9:30 p.m. Be on time for the start of each session if you want to see moonrise. Near the end of each session, Saturn will be rising into good view. Currently Saturn's rings are tipped only one degree from edgewise, and appear as a line of light extending to the sides of the planet -- Saturn kabob! The rings won't be seen so close to edgewise again until next February, and then not again until 2038-39.

Sunday, September 10

About 45 minutes after sundown (depending on your latitude) the waning gibbous moon has just risen a little north of east, with Saturn 20 degrees to its upper right. Saturn's rings, just over a degree from edge-on, appear through a telescope as a very narrow line of light piercing the planet -- Saturn kabob!

Monday, September 11

Even though the moon is three days past Full, it still rises before nightfall, providing light for late-working farmers to bring in the harvest.

Tuesday, September 12

Jupiter is the bright evening "star" in SSW at dusk. Mars is then low in WSW twilight glow, 34 degrees to Jupiter' lower right. During October, Venus will emerge from the Sun's brilliant glare to the lower right of Mars, and in mid-November all three planets will form a tight gathering.

Wednesday, September 13

Four and a half hours after sundown the waning gibbous moon is in E with the Pleiades star cluster 11 degrees to its left. To the naked eye, the Pleiades appear to consist of only a handful of stars; with optical aid several more of the hundreds of stars in this open cluster are seen.

Thursday, September 14

Saturn is at opposition and is up all night: Low in E to ESE at dusk, high in S in the middle of the night, and low in W to WSW at dawn. Look about 1-1/2 hours after sunset, and you'll catch the two largest planets at equal altitudes above the horizon: Jupiter in SW, and Saturn in ESE.

Four and a half hours after sunset the moon is low in E to ENE with the Pleiades, or Seven Sisters, 9 degrees to its upper left. Aldebaran, the eye of Taurus, is 6 degrees lower left of the moon. At dawn Friday, the moon is high in S with ruddy Aldebaran 4 degrees to its lower left.

Friday, September 15

Four and a half hours after sunset the moon is just risen in the ENE with first magnitude Aldebaran 6 degrees to its upper right. The Pleiades glitter 14 degrees above Aldebaran. The Arabs named Aldebaran "The Follower", because the star chases the Pleiades across the sky.

At dawn Saturday the moon, approaching Last Quarter, is high in SSE with Aldebaran 9 degrees to its right.

Saturday, September 16

At dawn Sunday the moon is high in SE. Aldebaran, the fiery eye of Taurus the Bull, is very high in south, 21 degrees upper right of the moon. Reddish Betelgeuse, the shoulder of Orion, shines 11 degrees lower right of the moon, which is now slightly less than half full.

Sunday, September 17

Look in ESE an hour before sunrise Monday for the waning crescent moon with Betelgeuse in Orion 17 degrees to its right. Procyon, the Little Dog Star, lies a similar distance below the moon, and the Gemini Twins, Pollux and Castor, are about as far to the moon's left. Given the moon travels some 13 degrees eastward against the background stars daily, can you guess where will it appear Tuesday morning at this time?

Monday, September 18

Winter stars are back -- if you look for them in the morning! At dawn Tuesday the thin crescent moon is in the ESE. Look for the Little Dog Star Procyon, 11 degrees to moon's lower right. Sirius, the Dog Star and brightest in the sky, twinkles 26 degrees to the lower right of Procyon. The Gemini Twins shine to the crescent moon's upper left. Betelgeuse, the shoulder of Orion the Hunter, shines far to the moon's upper right. Sirus, Procyon, and Betelgeuse form the Winter Triangle, which graces our sky at dusk from January through early May.

Tuesday, September 19

One and a half hours before sunup Wednesday the waning crescent moon is in the east. Using binoculars, look for the Beehive star cluster 7 degrees upper left of the moon. Procyon is 15 degrees to moon's upper right, and Regulus, the heart of Leo, is 24 degrees to moon's lower left. Watch the moon close in on Regulus in the following two mornings.

Wednesday, September 20

Find a place with a good unobstructed view of the western horizon. Return to this place, nightly if you can, to watch sunset. Do you think the sun sets at the same place along the horizon each day? At this time of year, for the next month, the sun changes its setting place by about half a degree (one solar diameter) from one evening to the next. Within a week, the change is very evident.

Thursday, September 21

Look very low in east an hour before sunrise Friday for the slender crescent moon with Regulus 5 or 6 degrees to its upper left. That glow you see on the moon's dark side is earthshine, or sunlight reflected off the Earth to illuminate the moon.

Friday, September 22

Forty-five minutes before sunup Saturday is the last chance to see the Old Moon. Look very low, due east, for the thin crescent with Regulus, the heart of Leo the lion, 16 degrees above. Autumn will begin at 8:13 a.m. EDT Saturday as the Sun, traveling south, passes directly over Earth's equator. This event is called the autumnal equinox.

Saturday, September 23

On this first night of autumn, blue-white Vega in the Summer Triangle is nearly overhead at dusk, while yellow-orange Arcturus shines in the west, and the Great Square of Pegasus stands on one corner like a baseball diamond in the east. Keep track of these stars each clear evening at dusk as the season progress.

Sunday, September 24

The New moon occurs today at 12:55 p.m. EDT, but most casual viewers in the U.S. won't see the young crescent until early Tuesday evening. Bright Jupiter grazes the 4.5-magnitude star Omega Ophiuchi at 7:54 p.m. EDT. With a telescope, watch as Jupiter's south polar region glides past the star. If you're in western North America, closest approach is already over by nightfall, and you can watch Jupiter pull away from the star.

Monday, September 25

Look early, 15 minutes after sunset, for the young crescent moon and Venus very low, between W and WSW. Venus, the evening "star" is 7 degrees to moon's right. You'll need binoculars, perfectly clear skies, and a horizon free of obstructions. Observers in southern states will see the moon and Venus more easily, perhaps even with unaided eye.

Tuesday, September 26

Look very low in the WSW half an hour after sundown for the thin crescent moon. As the sky darkens, use binoculars to search for Mars 11 degrees to moon's upper left, nearly one-third of the way from the moon toward Jupiter.

Wednesday, September 27

At dusk the moon is very low in SW to WSW with Mars within 3 degrees to its lower right. Binoculars give a beautiful view! That glow you see on the moon's dark side is earthshine, or sunlight reflected off the Earth to illuminate the moon.

Thursday, September 28

An hour after sunset the moon is low in SW with bright Jupiter 10 degrees to its upper left. Reddish Antares is just 5 degrees lower left of Jupiter this week.

Friday, September 29

One hour after sundown the waxing crescent moon is low in SW with bright Jupiter now 5 degrees to its lower right. Antares, the heart of the Scorpion, is still 5 degrees to Jupiter's lower left. Look for Saturn low in ESE, at the same altitude above the horizon as Jupiter in SW. Telescopic views of both planets can be enjoyed at this time, but clearer views can be obtained when each planet is higher in the sky, earlier in the evening for Jupiter, later in the evening for Saturn.

For the next week until October 6, watch the moon, near Jupiter tonight, move closer to Saturn on each successive night.

Saturday, September 30

An hour after sunset the moon is in SSW. Look for bright Jupiter in SW, nearly 20 degrees to moon's lower right. The "Teapot" asterism, consisting of eight stars of 2nd and 3rd magitude in the constellation Sagittarius, the Archer, can be found to the lower left of the fat crescent as the sky darkens.


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