To the reader:
The Skywatcher's Diary for July 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 July issue, please 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 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/
Evening: Venus at greatest brilliancy (mag. -4.5), is easy to
spot in daylight! Just before sunset, look in W, to upper left of Sun, by
43 degrees on July 1, 27 degrees July 31. Use binoculars or a telescope
before or around sunset to observe Venus' crescent phase. On July 1, Venus
is 37% full and 0.5 arcminute across. By month's end, Venus is a larger
and thinner 11% full and 0.8 arcminute across. Prominent at dusk, Venus
sets 2 hr 20 min after sunset on July 1, and just 45 minutes after sunset
on July 31 (from lower Michigan). Venus passes near Regulus July 10 &
11. They are still within 3 degrees on July 15, forming a spectacular compact
trio with crescent Moon. Mars is bright reddish "star"
in SSW to SW at dusk, fading from mag -0.4 to 0.0. Moon passes by on July
20. Fading Mercury is very low in WNW at dusk, 18 or 19 degrees lower
right of Venus July 1-9.
Two planets at dawn: Jupiter is bright (mag. -2.3 to -2.5) in
ESE to SE, climbing high. Saturn (mag. +0.4 to +0.3) is in E to ESE,
14 to 12 degrees E (lower left) of Jupiter. Waning crescent Moon appears
near these planets on July 7 and 8 at dawn, then on morning of July
10, Aldebaran emerges along Moon's dark, earthlit edge, visible from
Northeast, Mid-Atlantic, and eastern Great Lakes states, and part of eastern
Canada. For more on event, see July 9, and visit website http://www.lunar-occultations.com/iota
Partial lunar eclipse best for westerners, morning of July 28: See
July 27.
Skywatcher's Diary: July 1999
In Skywatcher's Diary, morning events are described on the previous
date.
Thursday, July 1
At sunset, Venus is in west, 43 degrees upper left of the
setting Sun. Using binoculars, can you resolve Venus as a crescent? It will
become easier in coming weeks as Venus swings nearer to Earth and appears
as a larger, but thinner crescent. From Michigan and other locations in
northern U.S., the waning gibbous Moon rises in ESE about two hours after
sunset, shortly before Venus sets in WNW. Can you see both objects simultaneously?
Friday, July 2
This evening about an hour after sunset, two planets each
has a bright companion just under 6 degrees away: Venus in the west is accompanied
by the star Regulus to its upper left. Mars in SSW is accompanied by Spica
to its lower right. Watch for changes in both planet-star pairs in coming
weeks. Mercury is very low in WNW, 18 degrees lower right of Venus, their
narrowest separation during Mercury's current evening apparation.
Saturday, July 3
As the evening sky darkens, the Mars-Spica pair, 6 degrees
apart, is in SW, with golden Arcturus within 33 degrees above. Locate the
Big Dipper in NW, and use its handle to "follow the arc to Arcturus
and drive a spike to Spica." Which appears brighter, Mars or Arcturus?
Continue to compare them in coming weeks, to determine when they'll appear
equal in brilliance.
Sunday, July 4
The brightest objects visible an hour after sunset, in order,
are Venus low in W, Mars in SSW, Arcturus high in SW, and Vega high in E.
Monday, July 5
An hour before sunrise on Tuesday, the Last Quarter Moon
is in SE, with bright Jupiter 19 degrees to its left and a little lower.
Saturn is within 14 degrees lower left of Jupiter. Follow the Moon in daylight
hours until just after midday on Tuesday (midway between sunrise and sunset),
when the Moon sets in the west. Note the Moon at Last Quarter is 90 degrees
(one-quarter circle) west of the Sun and is half illuminated.
Tuesday, July 6
An hour before sunrise on Wednesday, the fat crescent Moon
is in ESE with bright Jupiter 6 or 7 degrees upper left. Saturn is about
twice as far to lower left of Jupiter.
Wednesday, July 7
On Thursday 1-1/2 hours before sunup, in the east, the waning
crescent Moon is accompanied by two planets: Bright Jupiter 10 or 11 degrees
upper right, and Saturn about half as far to the Moon's left or upper left.
Can you see Aldebaran very low in ENE, 25 degrees lower left of Saturn and
14 degrees below the Pleiades star cluster? On Saturday, from parts of northeastern
U.S., the Moon will occult or cover Aldebaran. More on Friday.
Thursday, July 8
In the eastern sky beginning two hours before sunrise on
Friday, four bright objects lie in a nearly straight line. In order from
upper right to lower left, they are: Bright Jupiter; Saturn 13 degrees to
its lower left; the crescent Moon; and first-magnitude Aldebaran, eye of
Taurus the Bull. Note also the Pleiades star cluster 11 degrees to Moon's
upper left, and the Hyades cluster within 4 degrees upper right and above
Aldebaran. Binoculars give good views of both clusters, and of Saturday
morning's Moon-star gathering! More Friday.
Friday, July 9
Moon's dark, earthlit edge suddenly uncovers Aldebaran
early Saturday morning. This occultation reappearance is visible
from Northeast, Mid- Atlantic, and eastern Great Lakes states, and part
of eastern Canada, east of a line from Charleston SC to Duluth MN. From
many locations, Aldebaran is hidden from view behind the Moon as it rises.
The reappearance of Aldebaran can be observed with unaided eye if it occurs
not too close to horizon, but is best enjoyed with binoculars or a telescope.
Times for selected cities: Chicago (star barely above horizon!) 3:16 am
CDT; Wilmington NC 4:04 am EDT; Norfolk VA 4:07; Washington DC 4:10; Philadelphia
4:11; New York and Pittsburgh 4:12; Boston (star 12 degrees up) 4:13; Cleveland
4:14; East Lansing MI and Toronto ON 4:16; Montreal 4:18; Sault Ste. Marie
4:21 am. In Michigan, time of Aldebaran's reappearance ranges from 4:15
am in far SE corner of state to 4:24 am on Isle Royale, but the star is
then at best 3 to 5 degrees above ENE horizon, on the eastern side of the
state. After the star's reappearance, watch the Moon gradually pull away
from it. The earlier disappearance of Aldebaran behind lower bright edge
of crescent Moon is visible from Boston at 3:23 am EDT, and from Montreal
at 3:28 am, but from both locations, the star is then only 3 degrees above
the horizon. For more, visit website of International Occultation Timing
Association, at: http://www.lunar-
occultations.com/iota
Saturday, July 10
Face west as evening sky darkens, and look for the star
Regulus, heart of Leo the Lion, only 1-1/4 degrees above brilliant Venus.
They'll appear slightly closer on Sunday.
Last chance to see the old Moon: An hour before sunrise on Sunday, the
thin old crescent is very low in ENE, about 16 degrees lower left of Aldebaran.
Starting with bright Jupiter well up in ESE and working your way toward
lower left, note the nearly straight-line arrangement of Jupiter, Saturn,
Aldebaran, and the crescent Moon. Extend the line farther, to the Sun, below
the NE horizon to Moon's lower left.
Sunday, July 11
Look west as darkness falls, and enjoy the closest pairing
of Venus and Regulus, as the planet passes only 1.2 degrees lower left of
the star tonight. Look each evening as they gradually spread apart. In a
few days, before they're even 3 degrees apart, the young crescent Moon will
join them in a spectacular close grouping! Venus attains greatest brilliancy
this week!
Monday, July 12
The Moon is New today at 10:24 p.m. EDT (7:24 p.m. PDT,
4:24 p.m. in Hawaii). On which evening will you first spot the young Moon?
Tuesday, July 13
From far southern and southwest U.S. within 30 minutes
after sunset, if you use binoculars, you have a chance to view the young
Moon setting in WNW. From San Diego, the Moon is only 25 hours past New.
The crescent should be visible with unaided eye in Hawaii, with faint 2nd-
mag. Mercury visible in binoculars 4 degrees to Moon's upper left.
Wednesday, July 14
First easy chance for the young Moon: Forty-five minutes
after sunset, look very low, between W and WNW for the thin crescent Moon
13 degrees lower right of Venus. As the sky darkens, look for Regulus 2.2
degrees upper right of Venus. Can you guess what will happen on Thursday
evening? Don't miss it! Mars-Spica have now spread to 10 degrees apart in
SW.
Thursday, July 15
An easy chance to see Venus in daylight: Just before sunset,
face west to see Venus about 2 degrees lower left of the crescent Moon.
This evening, don't miss the spectacular compact trio of the 3-day-old
crescent Moon, Venus, and Regulus! From lower Michigan an hour after
sunset, Venus-Regulus are below the Moon, within 2.7 degrees of each other,
and each just over 2 degrees from the Moon's sunlit edge. The striking triangle
easily fits within the field of binoculars. From places farther west, the
Moon is seen farther to upper left of Regulus. >From extreme western
Europe including the U.K., the Moon occults or covers Regulus.
Friday, July 16
At sunset, Venus is in W, about 14 degrees lower right
of the waxing crescent Moon. Binoculars and telescopes show Venus as a crescent,
two-thirds of an arcminute across and one-quarter full. As the sky darkens,
Regulus appears just over 3 degrees upper right of Venus. Mars is in SW,
with Spica 11 degrees lower right. The 3rd-magnitude star Alpha Librae,
or Zubenelgenubi, is the same distance to Mars' upper left. Binoculars show
that star, formerly the "northern claw" of the Scorpion, has a
close 5th-magnitude companion. Mars will pass just 2 degrees below Alpha
Librae on Aug. 7, and will pass 3 degrees above Antares, the Scorpion's
heart, on Sept. 17.
Skywatching at Michigan State University Observatory is held tonight
and Saturday, 9-11 p.m. if sky is clear. Featured will be telescopic views
of Moon and deep-sky objects, and naked-eye views of stars and two planets.
Saturday, July 17
At sunset the crescent Moon is in WSW, about 63 degrees
upper left of setting Sun. Venus is in W, 38 degrees upper left of Sun and
26 degrees
to Moon's lower right, a few degrees below the line joining Sun and Moon.
Today a telescope magnifying 48 power would give an image of Venus roughly
the same size and phase as the Moon viewed with unaided eye.
Sunday, July 18
An hour after sunset, low in W, Venus and Regulus are just
4 degrees apart. They are getting lower each night, and soon both will be
gone. On what night will you last see each? The Moon is in WSW, with Spica
and Mars to its left. Look again next three nights.
Monday, July 19
The Moon, nearing First Quarter phase, is in SW at dusk,
almost 90 degrees or one-quarter circle from the Sun. Note the Moon is almost
half full. The star Spica in Virgo is 6 degrees south (lower left) of the
Moon, while Mars is 12 degrees to Spica's upper left. In mid-October, nearly
a quarter of a year from now, the Sun will appear to pass just 2 degrees
N of Spica, rendering that star invisible from Earth for several weeks.
It is actually Earth's orbital motion around the Sun which causes the disappearance
of Spica each autumn.
Tuesday, July 20
In SW as the sky darkens, the slightly gibbous (more than
half full) Moon is accompanied by Mars 6 degrees below.
Wednesday, July 21
Low in W an hour after sunset, Venus and Regulus are 5
degrees apart. At nightfall the Moon, two-thirds full, is in the SW sky,
between a pair of 3rd-magnitude stars and 4 or 5 degrees from each. The
upper one is Zubeneschamali, the lower Zubenelgenubi, formerly marking the
northern and southern claws of the Scorpion but now designated Beta and
Alpha in Libra. Mars and Spica are about 13 and 25 degrees to Moon's lower
right.
Thursday, July 22
At sunset, the waxing gibbous Moon is nearly due south,
while Venus is nearly due west, 35 degrees upper left of Sun. Moon and Venus
appear a few degrees short of 90 degrees apart this evening. At dusk, look
for reddish Antares 13 degrees to Moon's lower left.
Friday, July 23
An hour after sunset, face south to find Antares twinkling
8 or 9 degrees south of (below) the Moon. In the SW, 14 degrees apart, Spica
twinkles about as much as Antares, but Mars twinkles little, if at all.
Saturday, July 24
Low, north of W at dusk, try for Regulus 6 degrees lower
right of Venus, or to its right as seen from southern states. Binoculars
help you spot Regulus, especially from N states. The red supergiant star
Antares, heart of Scorpius, is in S, 16 degrees to Moon's lower right.
Sunday, July 25
Between two and three hours after sunset, after the sky
has darkened, the Moon passes south while 4 or 5 degrees above the 3rd-magnitude
star Lambda Sagittarii, the top of the Teapot. Lambda is also called Kaus
Borealis, the "northern star of the bow" of the Archer. Four stars
to Lambda's lower left and three to its lower right complete the handle
and spout of the 8-star Teapot asterism, comprised entirely of 2nd and 3rd-magnitude
stars. The Milky Way passes nearby, but tonight's bright Moon washes it
out. Wait until Aug. 1, and the Moon will rise late enough to allow good
viewing of the Teapot and the Milky Way.
Monday, July 26
In SW an hour after sunset, Spica is 15 degrees right of
Mars and a little lower. Antares is in S, just over 30 degrees left of Mars.
Mercury passes inferior conjunction today, nearly between Earth and Sun,
and in 2nd week of August will emerge as a morning "star."
Tuesday, July 27
The Moon rises in ESE shortly before sunset. Approaching
Full overnight, it undergoes a partial lunar eclipse best for westerners
Wednesday morning. Greatest eclipse, when Earth's shadow reaches 40%
of the way across Moon, occurs at 1:34 am Hawaii time, 4:34 am PDT, 5:34
am MDT, 6:34 am CDT. Umbral eclipse lasts for 1 hour 12 min before and after.
Moon's encounter with dark core of Earth's shadow will not be seen along
and east of line from eastern MI through OH, WV, VA, to coast of NC; there
Moon sets before umbral eclipse gets underway. The farther west of that
line you are, the more of eclipse you'll see. Along line from western ND
to southeast corner of TX, Moon sets at mid-eclipse, and there the first
half of the eclipse is visible in brightening dawn as the Moon sinks in
WSW. From West Coast of U.S. and Canada, most of Alaska, and all of Hawaii,
entire umbral eclipse can be seen. In Hawaii, observers can look for Delta
Aquarid meteors around mid-eclipse, before twilight starts. From all locations,
Moon sets in WSW around sunrise on Wednesday.
Wednesday, July 28
At sunset, look for Venus low in W, 30 degrees to Sun's
upper left. Binoculars show Venus as crescent, 0.8 arcminute across and
14 percent illuminated. The Moon, just past Full, rises in ESE about 15
to 20 minutes after sunset from 48 states.
Thursday, July 29
From N states, it's hard to see Regulus in evening twilight;
using binoculars, look 7 degrees upper right of the soon-to-depart Venus.
>From S states, both are higher and easier in a darker sky. Mars is in
SW at nightfall. The 3rd-magnitude star Alpha in Libra is 5 degrees upper
left of Mars.
Friday, July 30
Tonight the waning gibbous Moon rises one-and-a-half hours
after sunset from the latitude of lower Michigan. For the next few evenings,
from northern U.S., the Moon rises only about half an hour later and 6 or
7 degrees farther north along the eastern horizon nightly.
Saturday, July 31
One-and-a-half hours before sunrise on Sunday, Orion, with
his two bright stars reddish Betelgeuse and blue-white Rigel, and his 3-star
vertical belt between, has just risen in east. The reddish first-magnitude
star Aldebaran, eye of Taurus, is above Orion and 14 degrees below the Pleiades
cluster. Saturn is in ESE, 23 degrees upper right of Aldebaran and 12 degrees
lower left of bright Jupiter. Note Jupiter and Saturn shine with a very
steady light. A telescope shows Jupiter's four bright moons and its cloud
belts, and Saturn's rings tipped 21 degrees from edge-on.
***** end of Skywatcher's Diary for July 1999 *****