Some daily events in the changing sky for April 16 – 24.
Friday, April 16
Saturday, April 17
Sunday, April 18
Monday, April 19
Tuesday, April 20
Wednesday, April 21
Thursday, April 22
Friday, April 23
Saturday, April 24
Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).
Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper Uranometria 2000.0 (stars to magnitude 9.75).
You'll also need good deep-sky guidebooks, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic if somewhat dated Burnham's Celestial Handbook. Read how to use your charts effectively.
Can a computerized telescope take their place? I don't think so — not for beginners, anyway (and especially not on mounts that are less than top-quality mechanically). As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."
This Week's Planet Roundup
Mercury is fading and dropping out of sight in the sunset, after pairing with Venus for the first half of April.
Venus (magnitude –3.9) shines brightly in the west-northwest during twilight, becoming a little higher and more obvious every week. It will climb higher in May and June but not by very much (for observers at mid-northern latitudes). Then it will gradually sink back down for the rest of the summer.
Mars, dimming into the distance at magnitude +0.5, shines very high in the southwest during evening. It's in Cancer, left of Pollux and Castor and above Procyon. Near it binoculars show the big Beehive Star Cluster, M44.
In a telescope, Mars is gibbous and shrinking: from 8.0 to 7.5 arcseconds in diameter this week. Can you still see its north polar cap? The cap is shrinking as the Sun rises higher on it in the late spring of Mars's northern hemisphere.
Jupiter (magnitude –2.1) is low in the dawn. Look for it above the eastern horizon about 45 minutes before your local sunrise time. Nothing else there is nearly so bright.
Saturn (magnitude +0.7, in the head of Virgo) is high in the southeast to south during evening. In a telescope Saturn's rings are tilted only 2.2° from edge-on. They'll narrow to 1.7° from mid-May through early June, then begin widening again. Now's a fine time to try for the more difficult of Saturn's moons with your telescope; see the May Sky & Telescope, page 61, and the April issue, page 47.
Uranus and Neptune are still in the glow of sunrise.
Neptune, however, is passing a historic milestone this month. For the first time since the planet was discovered in 1846, it has completed a full circuit of the sky and has returned very close to the point (near the Aquarius-Capricornus border) where Johann Galle first spotted it from Berlin Observatory on September 23rd of that year — following a prediction of its existence by Urbain Le Verrier based on its perturbations of Uranus. See The Return of Neptune.
Pluto (magnitude 14, in northwestern Sagittarius) is highest in the south before dawn.
All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.
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