Abrams Planetarium Skywatcher's Diary
April 1998
To the reader
The Skywatcher's Diary for April 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
Our May 1998 issue may be reprinted for free distribution on
National Astronomy Day, Saturday, May 2.
If you would like a printed sample of the April issue, send a long,
self-addressed stamped envelope to:
April 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/
The compact gathering of Venus, Jupiter,
and Moon at dawn on April 23 is very rare. Don't miss it! Venus-Jupiter
will appear even closer to each other at dusk on February 23, 1999, and
will be seen within half a degree of each other on six or seven other occasions
by the year 2025; but none of those pairings will have the Moon close by!
To enhance the drama and visual impact of the April 23 gathering, choose
a place with an unobstructed horizon between E and ESE, and plan to arrive
there in plenty of time to observe the actual risings of planets and Moon.
The time of rising of Venus and Jupiter in relation to the time of sunrise
is given in a table below. From the contiguous 48 U.S., nearby Canada,
and Hawaii, Venus and Jupiter will rise within a minute of each other,
and soon afterwards the old crescent Moon will clear the horizon to the
lower left of the planets; this happens within just 9 minutes after the
planets rise as seen from the East Coast, within 14 minutes after they
rise on the West Coast, and 19 minutes after the planets rise in Hawaii.
Once all three bodies have cleared the horizon, they'll be in their most
compact visible arrangement, fitting within a field just 2 degrees across
for viewers in Northeastern U.S., 4 degrees across for the West Coast,
and 5-1/2 degrees across for Hawaii. As Moon and planets rise through dawn
mists, enjoy the chorus of bird songs and watch the Moon slowly withdraw
from the planet duo, by half a degree -- one Moon's width -- per hour.
When to begin viewing the gathering of Venus, Jupiter, and Moon on
April 23: The farther south you are, the earlier before sunup the planets
will rise. From lat. 20 degrees N in Hawaii, the planets will rise 2 hr
18 min before sunrise on April 23. Here's how long before sunup Venus and
Jupiter rise for other places in U.S. and southern Canada:
| Lat 25 degrees N |
2 hr 10 min |
| Lat 30 degrees N |
2 hr 01 min |
| Lat 35 degrees N |
1 hr 53 min |
| Lat 40 degrees N |
1 hr 42 min |
| Lat 45 degrees N |
1 hr 30 min |
| Lat 50 degrees N |
1 hr 16 min |
Interpolating for latitude if necessary, subtract the appropriate interval
from your local sunrise time, which you can obtain from the U.S. Naval
Observatory Astronomical Applications webpage, at: http://aa.usno.navy.mil/AA/
Skywatcher's Diary: April 1998
Wednesday, April 1
One hour after sunset, a fat crescent Moon is in WSW, with Aldebaran, eye
of Taurus the Bull, 9 degrees lower right. Betelgeuse, shoulder of Orion,
is 14 degrees to Moon's left.
Forty-five minutes before sunrise on Thursday, look very low, between
E and ESE, for Jupiter rising 18 degrees lower left of brilliant Venus.
On the mornings of April 22 and 23, these two planets will appear only
about half a degree apart. Look daily!
Thursday, April 2
The Moon, approaching First Quarter phase and nearly half full, is high
in SW an hour after sunset. Reddish Betelgeuse is within 12 degrees to
Moon's lower left, and Rigel, Orion's foot, is 19 degrees below Betelgeuse.
Follow Orion for the rest of April as it sinks lower into twilight each
evening.
Friday, April 3
By this evening, Moon has passed First Quarter phase and so it appears
just over half full. Three bright stars appear rather near the Moon tonight
and Saturday. Tonight, look for Pollux and Castor, the Gemini twins, 4-
1/2 degrees apart above the Moon, and for the even brighter star Procyon
to Moon's lower left.
This Friday and Saturday, MSU Observatory will be open for public
viewing from 9:00 until 11:00 p.m. if skies are clear. Telescopes and binoculars
provide stikingly detailed views of the lunar landscape, especially near
the Moon's terminator (day-night boundary).
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. (There are
no shows on Easter Sunday, April 12.)
Saturday, April 4
The waxing gibbous Moon is high in south at dusk, with Procyon, in Canis
Minor, 13 degrees lower right. Sirius, the brightest nighttime star, is
twice as far lower right of Procyon. Tonight, people in most of U.S. and
Canada should advance clocks one hour.
Sunday, April 5
WSKY ... Radio Station of the Stars, Sundays 2:30 p.m. at Abrams
Planetarium. (There are no shows on Easter Sunday, April 12.)
Mercury passes inferior conjunction, nearly between Earth and Sun, on
Monday. In late April and early May, from southern US. and the Southwest,
Mercury will be visible very low in E in morning twilight, far to lower
left of Venus and Jupiter. But observers in northern states may not see
it at all or will need binoculars to glimpse it during this year's worst
morning apparition.
Monday, April 6
Face SE one hour after sunset to see Regulus, heart of Leo, about 6 degrees
lower left of Moon.
Tuesday, April 7
Moon is in SE one hour after sunset, with Regulus 6 or 7 degrees to its
upper right.
Wednesday, April 8
This evening, the Moon is about one-third of the way from Regulus toward
Spica, two first-magnitude zodiacal stars. Regulus in Leo is 19 degrees
to Moon's upper right, while Spica in Virgo is 35 degrees to Moon's lower
left. Watch Moon nightly for rest of week.
Thursday, April 9
At dusk, Spica is 24 degrees to Moon's lower left, Regulus is 30 degrees
to Moon's upper right.
Friday, April 10
One hour before sunset, watch for Moon rising within 3 degrees S of due
east. An hour after sunset, Moon is in ESE with Spica 12 degrees
below. Bright Arcturus is 30 degrees to Moon's left.
On Saturday morning, an hour before sunrise, brilliant Venus is low
in ESE with Jupiter 10 degrees lower left. Among the most visually striking
celestial happenings of this year is the close pairing of Venus
and Jupiter on April 22 and 23, with the old crescent Moon especially
nearby on the 23rd. Catch the joy of planet-watching by following the chase
as one planet closes in on the other until Apr. 23, then pulls away from
it thereafter.
Saturday, April 11
>From a place with unobstructed views toward east and west, try to observe
the setting Sun and rising Moon simultanously. It's easiest in New England,
but impossible tonight in the Southwestern U.S., where the Moon comes up
a few minutes after sunset. Watch for the Moon to rise about 8 degrees
south of due east. Tonight's Grass or Egg Moon, first Full Moon of spring,
is also the most distant Full Moon of this year. An hour after sunset,
look for Spica 5 degrees to Moon's south (lower right or right). By an
hour before sunrise on Easter Sunday, Moon is in WSW, with Spica 6 degrees
below.
Sunday, April 12
An hour after sunset, Moon has just risen some 13 degrees south of east.
Note the star Spica 13 degrees to Moon's upper right. This week, Moon rises
nearly an hour later nightly, and farther south each night.
Monday, April 13
Two hours after sunset, Moon is very low in ESE, 25 degrees lower left
of Spica.
Tuesday, April 14
Tonight, the waning gibbous Moon rises in ESE about 2-3/4 hours after sunset
(from latitude of lower Michigan). An hour before sunrise on Wednesday,
Moon is in SSW, with Antares, heart of Scorpius, 11 degrees to its lower
left.
Wednesday, April 15
An hour before sunrise on Thursday, Moon is in S to SSW, with reddish Antares,
heart of the Scorpion, 11 degrees lower right.
Thursday, April 16
An hour before sunrise on Friday, two brilliant planets, Venus and Jupiter,
are just 5 degrees apart in ESE. Venus is the brighter one, to the upper
right. They'll appear about one degree closer each morning. Also note the
location of the Moon. Look daily!
Friday, April 17
At nightfall in mid-April each year, Orion is low in WSW to W. Look for
his distinctive belt of three stars in a row, with reddish Betelgeuse above
and blue-white Rigel below. Extend Orion's belt to the left to locate Sirius,
the brightest nighttime star, in SW. Extend the belt to the right to find
bright Aldebaran, eye of Taurus, in W, and the Pleiades cluster in WNW.
Look early each clear evening for the next several weeks, keeping records
of which stars you see. All of these will be gone by the 3rd week in May.
Saturday, April 18
A spectacular close pairing of the two brightest planets will occur on
the mornings of Wednesday and Thursday, April 22 and 23, as Venus and Jupiter
appear only about half a degree apart. An hour before sunrise Sunday (tomorrow)
morning, the two are just over 3 degrees apart, with Jupiter lower left
of brighter Venus. Look between E and ESE. The Moon, approaching Last Quarter
phase and just over half full, is in SSE.
Sunday, April 19
An hour before sunrise on Monday, look low, between E and ESE, for Jupiter
2.3 degrees lower left of brilliant Venus. The Moon, now a fat crescent,
is in SE. Moon and planets are fascinating to watch all this week. Don't
miss Thursday's spectacular gathering!
Monday, April 20
An hour before sunup on Tuesday, a fat crescent Moon is in E with Venus
and Jupiter, now within 1.5 degrees apart, some 25 degrees to Moon's lower
left. Jupiter is to Venus' lower left. Watch the order of the three bodies
change within the next few mornings.
Tuesday, April 21
A gathering of the three brightest objects will be strikingly beautiful
on Wednesday morning and spectacular on Thursday. Face ESE an hour before
sunrise. From Michigan and middle of the U.S. on Wednesday, Venus will
be within 12 degrees to Moon's lower left, while Jupiter will be 0.6 degree
to Venus' lower left.
Wednesday, April 22
Do not miss the remarkable gathering of Venus, Jupiter, and the crescent
Moon on Thursday morning. The best time to look, from most locations
in U.S. and southern Canada, may be about one hour before sunrise. For
the most dramatic effect, go out in time to watch the close pair of planets
rise ahead of the Moon. For details on the gathering for all locations
in U.S. and southern Canada between latitudes 20 and 50 degrees north,
see the article on the compact gathering
at the beginning of this diary.
Here are the specifics on Thursday morning's gathering for observers
in lower Michigan:
In the Lansing area, Venus and Jupiter rise within half a minute of
each other at 5:08 a.m. EDT, in a dark sky only 10 minutes after astronomical
twilight begins (when Sun is 18 degrees below horizon). The planets rise
27 arcminutes (just under half a degree) apart, about 7 degrees south of
due east. Jupiter is to the right of Venus and slightly lower. The lunar
crescent begins rising just to the lower left of the planet pair at 5:15
a.m. and concludes its rising by 5:18 a.m. Starting then, the gathering
of three objects is completely visible, provided there are no obstructions
on the horizon. At 5:18 a.m. EDT, the width of the gathering, from Jupiter
to the far lower left edge of the illuminated crescent Moon, is 2.2 degrees.
Nautical twilight (Sun 12 degrees down) is at 5:38 a.m., when the grouping
of Moon and planets is some 11 degrees south of due east and is 3 to 5
degrees above the horizon. By 5:44 a.m., one hour before sunrise, the gathering
is 4 to 6 degrees above the horizon, 12 or 13 degrees south of due east,
and may offer the most pleasing view. The Sun rises at 6:44 a.m.
For times in Detroit, subtract 6 minutes from the times listed above;
for Port Huron, subtract 8 minutes. For Grand Rapids, add 5 minutes.
Thursday, April 23
On Friday about 45 minutes before sunrise, the last thin old crescent Moon
has just risen in east. Some 16 degrees to Moon's upper right is brilliant
Venus with Jupiter 1.3 degrees to its upper right. Using binoculars, try
for Mercury rising in the bright twilight glow 5 or 6 degrees to Moon's
lower left. Moon and Mercury are easier to see from southern states.
Friday, April 24
On Saturday an hour before sunrise, look very low, between E and ESE, for
two bright planets 2.2 degrees apart: Jupiter to upper right of brighter
Venus.
Saturday, April 25
On each successive morning now, Venus and Jupiter are nearly one degree
farther apart. On Sunday, they're 3 degrees apart. Look 45 minutes to an
hour before sunrise.
Sunday, April 26
New Moon occurs at 7:41 a.m. EDT today and is not visible, except from
Hawaii, where it may be glimpsed briefly at dusk.
Monday, April 27
First chance to see young Moon: Half an hour after sunset, look very low,
10 degrees N of due west. As sky darkens, look for first- magnitude Aldebaran,
eye of Taurus, about 10 degrees to Moon's upper left, and the Pleiades
cluster, nearly as far to Moon's upper right.
Tuesday, April 28
An hour after sunset, look for Moon low in W to WNW. Aldebaran is to Moon's
lower right, by 3 degrees along E Coast, 5 degrees from W Coast, 6 degrees
from Hawaii.
Wednesday, April 29
An hour after sunset, crescent Moon is in W, with Betelgeuse 11 degrees
lower left.
Thursday, April 30
An hour after sunset, face west. Pollux and Castor, Gemini twins, are 4-
1/2 degrees apart, 16 degrees above Moon, while Procyon, Little Dog Star,
is 18 degrees to Moon's left.
