To the reader:
The Skywatcher's Diary for August 1999 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 issue of the Sky Calendar is available over the Internet.
It can be viewed via the World-Wide Web at http://www.pa.msu.edu/abrams/SkyCalendar/Index.html
If you would like a printed sample of the August issue, please send a
long, self-addressed stamped envelope to:
August Sky Calendar
Abrams Planetarium
Michigan State University
East Lansing, MI 48824
Each month, the Department of Physics and Astronomy at Michigan State
University makes the Skywatcher's Diary available over the Internet. It
can be accessed at http://www.pa.msu.edu/abrams/SkyWatchersDiary/Diary.html
Current and back-issues of the Skywatcher's Diary are available in our
archives at http://www.pa.msu.edu/abrams/SkyWatchersDiary/Archives.html
ftp://www.pa.msu.edu/pub/swd/
Planets at dusk: Venus in early August can still be glimpsed setting
just N of west in bright twilight; see August 1. From latitude of lower
Michigan, Venus sets 40 minutes after sunset on Aug. 1, and right at sunset
Aug. 10. Mars is in SSW to SW at dusk; it appears as the 3rd brightest "star"
at nightfall, ranking after zero-magnitude Arcturus and Vega. Mars
ends month 11 degrees west (right) of first-magnitude reddish Antares, "Rival
of Mars" and heart of the Scorpion.
Planets rising in late evening: Bright Jupiter rises 16
degrees N of east 3 hr 20 min after sunset on Aug. 1, and within 2-1/4 hours
after sunset on Aug. 31, from latitude of lower Michigan. Saturn
rises 12 degrees lower left of Jupiter within 40 minutes later.
Planets at dawn: Jupiter is brightest morning "star"
until Venus emerges late in month. Jupiter at dawn starts August high in
SE, and drifts through S and SSW as month progresses. Saturn is 12
degrees E of Jupiter. Mercury: 2nd through 4th weeks, very low, 20
degrees N of E. Venus: Rises 9 degrees N of E 35 minutes before sunrise
on Aug. 27, 65 minutes before sunup on Aug. 31, from latitude of lower Michigan.
Optical aid shows Venus as thin crescent nearly 1 arcminute across.
Solar eclipse on August 11: See August 10 and 11.
A great year for the Perseid meteor shower: See August 11 and
12.
Skywatcher's Diary: August 1999
In Skywatcher's Diary, morning events are described on the previous
date.
Sunday, August 1
Just before sunset, as the solar disk settles on the WNW
horizon, look low in W for Venus. From latitude of East Lansing MI and Boston,
Venus is due west 4 minutes before sunset, but is only 8 degrees above the
horizon. Venus' disk is 0.8 arcminute across, large enough for binoculars
to reveal it's now a crescent, just over 10 percent full. This evening Venus
set 40 minutes after sunset from latitude of East Lansing MI and Boston,
and a full hour after sunset from lat. 30 degrees N. Venus sets about 5
minutes earlier each day. On what date will you last see it as an evening
"star"?
Catch the waning gibbous Moon rising 2 or 3 degrees S of due east just
over 2-1/2 hours after sunset. Another hour later, watch for bright Jupiter
rising in ENE, some 27 degrees to Moon's lower left.
Monday, August 2
On Tuesday through Thursday mornings, about one and a half
hours before sunup, the southeastern sky is adorned by the Moon and two
bright planets. On Tuesday their arrangement, in order from right to left,
is Moon, Jupiter, Saturn, spaced at intervals of about 12 degrees. The star
Aldebaran, eye of Taurus, is in the east, about 23 degrees lower left of
Saturn. Binoculars give fine views of the Hyades star cluster in the same
field as Aldebaran, and the more compact Pleiades cluster 14 degrees above
Aldebaran.
Tuesday, August 3
At nightfall Mars in in SW with 3rd-magnitude Alpha in Libra
3 degrees to its upper left. First-magnitude Antares, heart of the Scorpion
and "Rival of Mars", is in SSW. Watch Mars pass 2 degrees below
Alpha Librae at week's end, and within 3 degrees above Antares in mid-September.
On Wednesday morning 1-1/2 hours before sunrise, the Moon is approaching
Last Quarter phase high in SE, with bright Jupiter about 5 degrees to its
upper right, and Saturn about 10 degrees to Moon's left. These mornings
with Moon near half full are excellent for using binoculars to see craters
and other lunar surface features near the Moon's terminator (day-night boundary).
There the Sun is setting and shadow are long.
Wednesday, August 4
Some 4-1/2 hours after sunset, locate bright Jupiter in
east, with Saturn 12 degrees lower left, and the fat waning crescent Moon
within 5 degrees below Saturn. By 1-1/2 hours before sunrise on Thursday,
Moon is well up in ESE, with Saturn about 6 degrees upper right and Jupiter
another 12 degrees upper right of Saturn. Note Aldebaran, eye of Taurus,
18 degrees to Moon's lower left. Be sure to look again on Friday morning!
Thursday, August 5
About five hours after tonight's sunset, locate bright Jupiter
in E with Saturn 12 degrees to its lower left. A line from Jupiter to Saturn
extended about 18 degrees to Saturn's lower left locates the Moon, one-third
full, just rising in ENE. As the Moon rises higher during Friday's morning
hours, watch it gradually drift along the southern arm of the V-shaped Hyades
cluster and approach first-magnitude Aldebaran, eye of Taurus, the Bull.
Use binoculars or a telescope to watch Moon's darker earthlit side suddenly
uncover 3.6-mag. Gamma Tauri, the star marking point of the "V".
Here are sample times (all Friday a.m.) when star emerges: MST/PDT:
Tucson 1:42; Vancouver 2:13. MDT: Denver 2:56. CDT: Austin
3:30; Kansas City 3:53; Chicago 4:00; Winnipeg 4:15. EDT: Atlanta
4:30; Washington DC 4:49; Boston and East Lansing MI 5:02; Toronto 5:06.
Binoculars give a very striking view of the crescent Moon, Aldebaran,
and the Hyades all in one view. For more, visit IOTA website at: http://www.lunar-occultations.com/iota
Friday, August 6
On Saturday, as dawn begins to brighten, the two brightest
objects in the sky are the crescent Moon in the east and Jupiter higher
in SE; Saturn and Aldebaran lie along the line joining them. Reddish Betelgeuse,
Orion's shoulder, is 14 degrees below Moon, and blue-white Rigel, the Hunter's
foot, is in ESE, 19 degrees right of Betelgeuse. Orion's belt is marked
by a vertical line of three stars midway between Betelgeuse and Rigel.
Saturday, August 7
In SW at nightfall, Mars passes 2 degrees below a 3rd-mag.
star, Alpha Librae. Binoculars show the star has a close 5th-mag. companion.
An hour before sunrise on Sunday, Orion the Hunter is in E to ESE, to
the crescent Moon's right, while the "Twin" stars of Gemini, Castor
4-1/2 degrees above Pollux, lie in ENE, about 20 degrees to Moon's lower
left. Mercury, of mag. +1.2 and just rising in ENE 11 degrees lower right
of Pollux, will brighten sharply in coming days.
Sunday, August 8
An hour before sunup on Monday, the last easy-to-see thin
old crescent Moon is low in ENE. Note bluish earthshine illuminating the
side not directly lighted by the Sun. Find Pollux about 10 degrees to Moon's
upper left, and Castor 4-1/2 degrees above Pollux. First-magnitude Mercury
has just risen in ENE, some 9 degrees to Moon's lower left.
Monday, August 9
In ENE on Tuesday an hour before sunrise, a line from Castor
to Pollux, 4-1/2 degrees long, extended 11 degrees downward past Pollux
locates Mercury, now of mag, +0.8. If your horizon is unobstructed and if
the sky is very clear, watch for the old crescent Moon rising 4 or 5 degrees
lower left of Mercury. Binoculars will help located the hairline Moon, some
25 hours before New in eastern U.S.
Tuesday, August 10
Wednesday's New Moon (at 7:08 a.m. EDT) brings with it
a total solar eclipse. Centerline of the path of totality for Wednesday's
eclipse begins in the North Atlantic south of Nova Scotia, and after crossing
the ocean, passes over southwestern England, northern France, southern Germany,
Austria, Hungary, Romania, Bulgaria, the Black Sea, Turkey, Iraq, Iran,
Pakistan, and India. In northeastern U.S. and nearby Canada, a partial
eclipse is deepest as Sun's disk first completely clears ENE horizon,
at these times on Wednesday morning for selected cities: Boston at 5:50
a.m. EDT; Montreal 5:53 a.m.; New York 6:05 a.m.; Philadelphia 6:11 a.m.;
Toronto 6:20 a.m., Washington DC 6:21 a.m. The concluding moments of the
eclipse can seen immediately after sunrise as far west as Cape Hatteras
NC, Richmond VA, London ON and Sault Ste Marie MI, provided the observer
has an unobstructed view of the ENE horizon. Observers in New England, Nova
Scotia, and other places in eastern U.S. have a chance to see the Moon's
shadow projected on Earth's atmosphere before sunrise Wednesday morning;
for more, see article, "The Eclipse Outside of Totality" on pp.
108-110 of August Sky & Telescope.
Wednesday, August 11
Those fortunate enough to be in the narrow path across
Europe and SW Asia will enjoy today's total solar eclipse, the last
of the 20th Century. The next one, on June 21, 2001, is more remote, crossing
southern Africa and Madagascar. The next total solar eclipses to cross the
U.S. will come on August 21, 2017 (Oregon to South Carolina) and April 8,
2024 (Texas to Maine).
Even if you can't travel to the path of today's solar eclipse, the fact
the Moon is New today will compensate you with dark night skies and fine
views of this year's Perseid meteor shower! The shower is at its best
overnight tonight and Thursday night, August 11-12 and 12-13. You're most
likely to see the greatest numbers of meteors in the predawn darkness hours
of Thursday and Friday, until twilight begins to brighten.
Thursday, August 12
The Moon sets within an hour after sunset from northern
U.S., but you can still see it if the sky is very clear and you look early.
From lower Michigan 30 minutes after sundown, the thin crescent is just
3 or 4 degrees above the horizon and 9 or 10 degrees north of due west.
Binoculars give a good view.
After nightfall the rest of the night is dark and moonless, ideal for
observing the peak of the Perseid meteor shower. Expect the greatest number
of meteors in Friday's morning hours, until dawn begins to brighten.
Friday, August 13
Thirty minutes to an hour after sunset, the waxing crescent
Moon is easy to see low in the west. The next three brightest objects visible
then, in order, are orange Arcturus well up in WSW to W; blue-white Vega
very high in E to ESE; and orange Mars in SW.
An hour before sunrise bright Jupiter, high in SSE, far outshines all
other "stars". Next in brightness are the stars Vega low in NW
and Capella high in ENE; then the planets Mercury very low in ENE, and Saturn
in SE, 12 degrees lower left of Jupiter. Today Mercury appears at its greatest
angular distance from the Sun this time around, 19 degrees.
Saturday, August 14
An hour before sunrise on Sunday, locate Orion the Hunter
in ESE, and the Gemini twins, Castor 4-1/2 degrees above Pollux, in ENE.
Mercury twinkles very low in ENE, 13 degrees below Pollux. Procyon is very
low in E, 17 degrees right of Mercury and 26 degrees lower left of Orion's
shoulder, Betelgeuse. In another 15 minutes, follow Orion's belt downward
to the horizon where you will watch for the rising of Sirius, the Dog Star,
in ESE. Betelgeuse, Procyon, and Sirius form the nearly equilateral Winter
Triangle.
Sunday, August 15
Evenings this week are excellent for using binoculars or
a small telescope to study lunar landscape features along the Moon's sunrise
terminator (day-night boundary). An hour after sunset look low in WSW to
find Spica 8 degrees lower left of the waxing crescent Moon. Golden Arcturus
is 27 degrees to Moon's upper right. Use the handle of the Big Dipper to
"Follow the arc to Arcturus and drive a spike to Spica."
Monday, August 16
An hour after sunset, the crescent Moon is nearly one-third
full in SW to WSW. Spica is about 10 degrees to Moon's lower right, while
reddish Mars is about 20 degrees to Moon's left. The red supergiant star
Antares is in SSW, 20 degrees left of Mars. In mid-September Mars and Antares
will be less than 3 degrees apart. Keep track of these two "red stars"
for the next month as Mars closes the gap between them.
Tuesday, August 17
An hour after sunset, the fat crescent Moon is in SW, with
Mars about 9 or 10 degrees lower left. Antares is in SSW, about twice as
far to the left of Mars. Between Mars and Antares, look for a vertical "fence"
of three stars in a slightly curved line; these mark the head of the Scorpion.
Mars will pass closely above the middle star on Sept. 6. Look nightly to
follow the progress of Mars.
Wednesday, August 18
Face the setting Sun, then look 90 degrees or a quarter-circle
to your left (over your left shoulder) to see the First Quarter Moon, with
its right half illuminated. As the sky darkens, Mars is about 7 degrees
to its lower right. Antares is 19 degrees left of Mars.
Thursday, August 19
A slightly gibbous Moon (just over half full) is in SSW
at dusk. Antares is 9 degrees to its south (lower left), while Mars is 18
degrees west (right) of Antares.
Friday, August 20
Venus passes inferior conjunction today, 8 degrees south
of Sun, as planet nearly between Earth and Sun and moves into morning sky.
On what date will you first see Venus as a morning "star"? See.
Aug. 28.
Saturday, August 21
This is not a good evening for viewing the Milky Way! Tonight
the Moon appears above the Teapot of Sagittarius, only 10 degrees fom the
direction of the center of our Galaxy. The flood of bright moonlight makes
it difficult to see the wonderful star clouds, star clusters, and nebulae
along the belt of the Milky Way. Wait until at least Aug. 29, when the Moon
will rise after darkness falls.
Sunday, August 22
The Moon, approaching due south at nightfall, is 5 degrees
above 2nd-magnitude Sigma Sagittarii, brightest star in the handle of the
Teapot.
Monday, August 23
High in the southern sky an hour before sunrise, brilliant
Jupiter is accompanied by Saturn 12 degrees to its east (left). This week,
Saturn's rings are tipped 21 degrees from edge-on, the best for this year.
Tuesday, August 24
In SW to SSW an hour after sunset, Mars and Antares are
15 degrees apart this evening and Wednesday. Which appears brighter, Mars
or Antares, the "Rival of Mars"?
Wednesday, August 25
Compare the colors of Arcturus, well up in west an hour
after sunset, and Vega, nearly overhead.
Thursday, August 26
Full Moon occurs at 7:48 p.m. EDT. Tonight's Green Corn
Moon or Grain Moon rises south of east 3 to 16 minutes after sunset from
all of U.S. except Alaska, and remains visible until shortly after sunrise
on Friday.
Friday, August 27
This weekend Saturn is 14 degrees from the Pleiades star
cluster (their least separation this year), and for the next few months
moves slowly retrograde, away from the Pleiades.
Saturday, August 28
Half an hour before sunrise on Sunday, from a place with
an unobstructed view of the eastern horizon, locate Venus very low, about
6 degrees north of due east. Using binoculars, scan the horizon nearly 11
degrees left of Venus to find Mercury. Using binoculars or a telescope,
follow Venus until sunrise and observe its very thin crescent, nearly one
arcminute across but only 4 percent illuminated.
Sunday, August 29
The Moon rises closely north of east just after the end
of evening twilight. Jupiter rises about half an hour later, within 20 degrees
to Moon's lower left. As dawn begins to brighten on Monday, Moon is high
in SSW, with Jupiter and Saturn to its upper left.
Monday, August 30
About 3-1/2 hours after sunset, the waning gibbous Moon
is low in east with Jupiter 6 degrees upper left, and Saturn 12 degrees
lower left of Jupiter. In another hour, look for the Pleiades cluster 14
degrees left of Saturn, and Aldebaran, the "Follower of the Pleiades"
and eye of Taurus, 14 degrees below the Pleiades. Moon and Jupiter remain
close together for the rest of the night; as dawn begins to brighten on
Tuesday, they're high in the south, with Jupiter 4 degrees above the Moon.
Tuesday, August 31
About 3-1/2 hours after sunset, Moon is low in eastern
sky with Saturn 4 degrees upper left, and bright Jupiter about 11 degrees
upper right. Moon-Saturn remain only 3 or 4 degrees apart for the rest of
the night, ending high in the south an hour before sunup.
*****end of Skywatcher's Diary for August 1999*****