The morning sky's monopoly of the planets began to break up in March when Mercury moved into the evening sky. Mercury actually returns to the morning sky late this month (in inferior conjunction on the 22nd), but it doesn't help much. Pluto shifts to an evening star when it goes through opposition from the sun on the 20th. And the three brightest planets of this month, Mars, Jupiter, and Saturn,
are all moving retrograde (westerly past the stars) before the end of April, a sure sign that they will very soon enter the evening sky. By early July, in fact, all the planets will be in the evening sky, a remarkable reversal in only a few months.
When the outer planets begin moving retrograde, they are still morning stars technically; but they are also becoming part of the evening scene, in the sense that they are up before midnight. So it is this month with Saturn, Mars, and Jupiter. By mid-month, Saturn is up by 8, Mars an hour later, and Jupiter close to midnight. All rise about an hour earlier by month's end, Saturn only a short time after sunset. The three planets, with the bright nearby stars Spica in Virgo and Antares in Scorpius, are strung out across the sky virtually in line, easily seen as morning stars in the east and southeast from an hour after midnight until dawn. Lowest and brightest in the east is Jupiter, then reddish Antares - a little below the line, Mars - second brightest, Saturn, and finally Spica - highest. Though best seen after midnight, the string of objects begins coming up much earlier; at 11 p.m., for example, all can be seen but Jupiter. Make a point of looking for the moon from the 15th through the 20th as it moves past each object in turn. It will be exceptionally close to Saturn during the night of the 16th, to Mars on the following night.
April 1: The moon, in Cetus, becomes new and enters the evening sky at 7:10 a.m., EST, but we won't see it for two or three days, when it separates far enough from the sun to its left.
April 2-5: Mercury is in conjunction with the moon about 7:00 p.m., EST, on the 2nd, north of the moon in the evening sky. It is also at its maximum separation to the sun's left, placing it favorably in the evening sky.
April 4: Mars has been drifting left from Saturn, but stops today and moves toward it again. This is the retrograde motion that begins a few weeks before Mars is at opposition from the sun in early May. Watch the planet brighten now, double in the next five weeks!
April 5: Aldebaran and Taurus's ''face'' are below the moon tonight. Look for a reddish star with a ''V'' of fainter stars attached.
April 6: The crescent moon is virtually between the ''horns'' of Taurus tonight, the brighter El Nath above and Tau Tauri below.
April 8-9: The moon is in Gemini on the 8th, reaching first quarter phase at nine minutes before midnight.
April 11: Regulus, in Leo, is directly below the gibbous moon tonight, with the circular group of stars marking Leo's head above the moon.
April 13: The moon is at perigee (nearest earth) early today. It's in Virgo tonight, about midway between Regulus, to the right, and Spica (Virgo's brightest star).
April 15: Only Spica can be seen within the bright glow of the moon tonight, full at 2:11 p.m., EST. Later at night, look for Saturn to the moon's left, Mars still further left and brighter.
April 16-18: The bright gibbous moon is just below Saturn when it passes the planet at about 8:00 p.m., EST on the 16th. Mars is to their left. But don't get mixed up on the evening of the 17th when it's Mars near the moon, with Saturn to their right. At about 6:00 p.m., the moon passes just below Mars. Both planets are covered (occulted) by the moon from some parts of the earth as it goes by them. Saturn's occultation, on the 17th, can be seen over the South Atlantic and adjacent lands, Mars's over Western Pacific and Indian Ocean regions.
April 20-21: The moon joins Jupiter in Sagittarius. They rise a little after midnight, and in about two hours they should be high enough in the southeast that you can see the teacup-shaped stars of Sagittarius to their right.
April 22: Mercury passes the sun today, between earth and sun (inferior conjunction), and enters the morning sky. Last quarter moon, in Capricornus, is at 7:26 p.m., EST, but the moon doesn't rise until about 2:00 a.m.
April 26: Apogee moon (farthest from earth) occurs today. The waning crescent is in Aquarius this morning.
April 27: Probably the last morning for the late crescent moon during this cycle.
April 29: The third of the bright morning planets, Jupiter, becomes stationary today, and begins moving westerly through the stars of Sagittarius again. Now all three, Saturn, Mars, and Jupiter, are moving retrograde, and the presence of bright stars nearby (Spica, Antares, and those of Sagittarius) should allow you to see their westerly drift over the next several weeks. All, of course, are approaching opposition from the sun. Still morning stars, they are up before midnight now and remain above the horizon past dawn.
April 30: The month ends with another new moon, in Aries, at 10:45 p.m., EST.