Sky at a Glance | April 4th, 2008

Some daily events in the changing sky for April 4 – 12.

Looking west in twilight
The thin waxing crescent Moon of April is always upright like a cup, or a Cheshire-cat smile, for those of us at mid-northern latitudes. On the evening of Tuesday the 8th it crosses the northern edge of the Pleiades cluster as seen from eastern North America. For clarity, the Moon in these diagrams is drawn three times its actual size. (European observers: move each Moon symbol a quarter of the way toward the one for the previous date.)

Friday, April 4

  • If it's April, we're coming into the height of Big Dipper season; the Dipper is already high overhead toward the north-northeast these evenings. All around it, galaxies are scattered. See the guide to finding the pair of them above the Great Bear's back in the April Sky & Telescope, page 51, and other telescopic sights among the Bear's feet on page 73.

    Saturday, April 5

  • New Moon (exact at 11:55 p.m. Eastern Daylight Time).

    Sunday, April 6

  • A small telescope will always show Titan, Saturn's largest and wildest moon. Tonight Titan is four ring-lengths to Saturn's east. A guide to identifying all six of Saturn's satellites that are sometimes visible in amateur scopes is in the April Sky & Telescope, page 58.

    Monday, April 7

  • Sirius, the brightest star in the evening sky, still shines moderately high in the south-southwest after sunset in early April. How early in twilight can you first spot it?

    Tuesday, April 8

  • The thin crescent Moon hangs hear the Pleiades in the west at dusk, occulting (covering) some of the Pleiades stars as seen from parts of the northeastern US and eastern Canada.

    Wednesday, April 9

  • The waxing Moon now forms a biggish triangle with the Pleiades and Aldebaran; it's hanging above them.

    Thursday, April 10

  • The red long-period variable star S Ursae Majoris, just off the Big Dipper, should be at maximum light (7th or 8th magnitude) this week. Use binoculars and the comparison-star chart in the April Sky & Telescope, page 70.

    Friday, April 11

  • The Moon (nearly first-quarter) passes very near Mars in Gemini tonight. Their closest approach, around midnight Pacific Daylight Time, is best seen from western North America.

    Saturday, April 12

  • First-quarter Moon (exact at 2:32 p.m. EDT).

    The Moon crossing the Twins
    As the Moon waxes thicker, it moves higher to the upper right and passes Mars in Gemini.

    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 foldout map in 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'll need a detailed, large-scale sky atlas (set of maps; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the enchanting though increasingly dated Burnham's Celestial Handbook). Read how to use them effectively.

    More beginners' tips: "How to Start Right in Astronomy".

    This Week's Planet Roundup

    Jupiter is getting high enough now in early dawn to show detail well in a telescope . The North Equatorial Belt (brown band just above center) remains wide and very dark. The South Equatorial Belt (just below center) has divided into northern and southern halves. A South Equatorial Belt Disturbance has created the irregular white markings near the left (following) limb. Note the very different colors of the belts in the in the northern and southern hemispheres. The Equatorial Zone, after being remarkably dark last year, has returned to its normal bright state. Christopher Go took this image on April 3, 2008. The time was 20:20 UT, and the System II central-meridian longitude was 32°. North is up (but remember that many telescopes will show south up).
    Mercury is lost in the glare of sunrise.

    So is Venus. . . or is it? How low does bright Venus (magnitude –3.8) really have to go before it disappears? We want your observations; see our article.

    Mars (magnitude +0.9, in the center of Gemini) shines in the southwest to west during evening, high over Orion. In a telescope Mars is just 6.5 arcseconds wide now — just a tiny blob. A telescope will, however, show that Mars is gibbous.

    Jupiter (magnitude –2.3, in eastern Sagittarius) glares in the southeast before and during dawn. The farther south you live, the higher you'll be able to observe it before dawn gets too bright.

    Saturn (magnitude +0.4, near Regulus in Leo) glows high in the southeast to south during evening. Fainter Regulus (magnitude +1.4) is a bit less than 3° from Saturn: to its right at dusk, and lower right of it later at night. Watch Saturn and Regulus draw a bit closer together for the rest of April.

    The two form a narrow triangle with Gamma (γ) Leonis, which at magnitude +2.1 is only a little dimmer than Regulus. It's located 8° to Saturn's north.

    Saturn, March 25, 2008
    Saturn with four of its satellites, shot on the evening of March 25th. Orange Titan is at top, Rhea is at top right, Dione is directly to Saturn's right, and Tethys is just to the planet's lower left. North is up. Scott Hammonds took the raw video frames in Florida using a Meade 10-inch Schmidt-Cassegrain telescope and a DMK 21AU04.AS camera; processing by Sean Walker.
    Scott Hammonds and Sean Walker
    Telescope users: there's more to Saturn than you may realize. See our Saturn observing guide in the April Sky & Telescope, page 66.

    Uranus and Neptune are still low before dawn.

    Pluto (magnitude 14.0, in northwestern Sagittarius) is well up in the south-southeast before dawn's first light.

    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 (UT, UTC, or GMT) minus 4 hours.

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