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Abrams Planetarium SKYWATCHER'S DIARY: April 1998
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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 Sky Calendar 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
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 via a World-Wide Web browser such as
Netscape or Internet Explorer, 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

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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.

***** end of Skywatcher's Diary for April 1998 *****