April Sky Chart; Northern Hemisphere gazer's guide

April 2: Mercury is at greatest westerly elongation (greatest distance to the right -- west -- of the sun). Ordinarily this puts the planet in best position for viewing as a morning star, since, to the sun's right, it rises before the sun and can be seen in the east during predawn darkness. But this is an unfavorable elongation, not because Mercury isn't far enough away from the sun (at about 28 degrees, it is as far to the right of the sun as it ever gets), but because of the direction along which this distance is measured.

April 5: Venus is at greatest easterly elongation, and this is a very favorable one! When eastm of the sun, a planet is to the sun's left, and therefore remains in the sky in the evening after sundown. Venus is 46 degrees to the left of the sun tonight, in a direction that takes it quite far north relative to the sun. Consequently, the planet is high in the sky at sunset and takes several hours to set. For this reason, and because it is such a brilliant object, Venus will be spectacular this month. Each clear night, it will appear high in the west very soon after sundown, long before the sky has darkened appreciably.

April 7: Mars has completed its retrograde (westerly) sojourn in Leo. It becomes stationary today, and then resumes its normal (easterly) motion.The planet is now well to the right of Regulus (in Leo) and the brilliant Jupiter, but it will be approaching them rapidly during the next several weeks, passing to the left (east) of Regulus in late April, of Jupiter in early May.

April 9: Pluto, at opposition from the sun, becomes an evening star.

April 13: The late crescent moon passes in front of Mercury this morning. The occultation occurs over the Southern Hemisphere, but the two objects are very near the sun's position and therefore above the horizon during daylight or morning twilight.

April 14: Perigee moon (nearest Earth) occurs about 21 hours before the new moon, and its effect will enhance the normally stronger spring tide that accompanies each syzygy (when sun, moon, and Earth are in line). Look for higher than usual tides tonight and especially tomorrow morning.

The bright star near Venus this evening is Aldebaran, in Taurus.

April 17: The slim crescent moon passes close to Aldebaran late this evening, covering the star (an occulaltation) over parts of the Northwestern United States and western Canada, where they are above the horizon at about 11 p.m., e.s.t., the time when the moon comes between the star and Earth. In the early evening tonight, Aldebaran will be close by the lower "horn" of the lunar crescent, while very brilliant Venus is also nearby.

April 21: The first quarter moon will set this evening in plenty of time to leave dark skies for viewing the Lyrid meteor shower after midnight.But this is not a very productive shower (about 15 shower meteors per hour), nor are its meteors usually very bright.

April 23-24: The waxing gibbous moon passes Mars, Regulus, and Jupiter all with four hours after midnight tonight, highlighting the close proximity of these three bright objects to one another. The moon will be west (to the right and above) of the three when they become visible in the east after dark. Then, as all rise and drift to the west, the moon will slide below Mars at about 2 a.m., e.s.t., and just barely below Regulus and Jupiter at two-hour intervals later. Saturn is the object to the left and below the moon. During the conjunctions this evening, the moon occults Regulus and Jupiter over the Southern Hemisphere.

April 25-26: The moon passes and occults (over the Southern Hemisphere) Saturn at about midnight e.s.t. this evening. It will be interesting to watch it approach the planet during the early evening, slide past just below and nearly touching, and then move away to the left (east) during morning hours. Mars, Jupiter, and Regulus are close together, to the west of the moon and Saturn.

April 26: Jupiter becomes stationary today and resumes its direct (easterly) movement through the stars. After approaching Regulus from the left for the past four months, the bright planet now moves away from it, back to the left (east).

April 26: The moon is at apogee, where it is farthest from Earth this month.

April 27: Communities that go on daylight time adjust their lives so that events occur one hour earlier, but at the same clock time. They do this by the technique of "advancing the clock" by one hour early this morning, thus converting what is called "standard" time to "daylight" time. Of course, the same effect could be accomplished by just doing things one hour earlier than we are accustomed to, but it's psychologically easier to do that if our clocks show the time as the same.

April 29: Mars passes Regulus again, going from right to left past the star. It did this last November, but then turned around and passed Regulus in March going from left to right, during its retrograde (westerly) loop. Having ended its retrograde motion early this month, it is now moving eastward once more.

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