Sky at a Glance | April 19th, 2013


Friday, April 19

  • Look left of the Moon this evening for Regulus and the Sickle of Leo, as shown at right.

    Saturday, April 20

  • The Moon now shines under Regulus after dark.

    Sunday, April 21

  • The Lyrid meteor shower should peak before dawn Monday morning local time. Most years it's quite weak, but there have been surprises. See our article Lyrid Meteor Shower in 2013.

    Monday, April 22

  • The two brightest points in the sky after dusk this week are Jupiter in the west and Sirius in the southwest. Midway between them is Orion. This lineup is lying down lower every week now. How late into the spring can you keep it in view?

    Dusk view
    Watch the Moon pair up with Spica and Saturn. (The Moon is positioned for twilight in the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date.)
    Sky & Telescope

    Tuesday, April 23

  • There's a bright gibbous Moon tonight. If you're out with a telescope, you'll notice that the Moon is creeping toward a star: Chi Virginis, magnitude 4.7. The Moon's invisible dark limb, just beyond the terminator, will occult the star for most of North America except the Northeast and north of the Great Lakes. Some times of the star's disappearance: at Washington, DC, 12:20 a.m. EDT; Miami, 11:58 p.m. EDT; Chicago, 10:47 p.m. CDT; Austin, 10:17 p.m. CDT; Denver, 9:07 p.m. MDT; Los Angeles, 7:52 p.m. PDT.

    Wednesday, April 24

  • Look close to the nearly full Moon for Spica tonight. The Moon occults Spica for parts of Central America, South America, and southern Africa; map and timetables.

    Thursday, April 25

  • Full Moon. A very slight partial lunar eclipse is visible from Europe, Africa, Australia, and most of Asia, centered on 20:07 April 25th Universal Time. Details.

  • The "star" near the Moon all night is Saturn, just two days away from its own opposition.

    Friday, April 26

  • Around the end of twilight this evening, the Moon rises below Saturn. With binoculars, look closer below Saturn for the wide double star Alpha2 and Alpha1 Librae, magnitudes 2.8 and 5.2, respectively.

    Saturday, April 27

  • Saturn is at opposition tonight: opposite the Sun as seen from Earth.

  • In early dawn Sunday morning, the red supergiant Antares sparkles below the waning gibbous Moon in the southwestern sky.


    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 guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

    Pocket Sky Atlas
    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

    You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability). As Terence Dickinson and Alan Dyer say in their invaluable 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

    Jupiter on April 22, 2013
    Jupiter's non-Red-Spot side on April 22nd. The dwindling giant planet appears only 70% as large now as it did at opposition last December. But that's still enough for many amateur scopes to show the color difference between the broad South and North Equatorial Belts, and the presence of the thinner North Temperate Belt compared to the absence of its southern equivalent. South is up.

    Mercury is lost in the glow of dawn.

    Venus and Mars remain hidden behind the glare of the Sun.

    Jupiter (magnitude –2.0, in Taurus) is the first "star" to come out in the west after sunset. It descends in the evening and sets around 11 p.m. Below Jupiter sparkles orange Aldebaran, and a similar distance above Jupiter is El Nath (Beta Tauri). Bright Capella shines to the upper right from there.

    In a telescope, Jupiter has shrunk to a disappointing 34 arcseconds wide.

    Saturn (magnitude +0.1, in Libra) is nearing opposition. It glows low in the east-southeast as twilight fades, well to the lower left of Spica and farther lower right of brighter Arcturus. Saturn rises higher all evening and shines highest in the south around 1 a.m. daylight saving time. It's at opposition on the night of April 27th.

    Saturn on April 15, 2013
    Saturn on April 15th, imaged by Christopher Go in the Philippines using a Celestron 14 scope and a Point Grey Research monochrome Flea3 (ICX618) camera with Chroma Technology LRGB color filters. South is up. "The polar hexagon is prominent on this image," he writes. "Note the white spots on the North North Temperate Zone."
    Christopher Go

    Carefully note the brightness of Saturn's rings with respect to the globe. Keep watch. The rings brighten for a few days around opposition due to the Seeliger effect: the solid particles of the rings preferentially reflect sunlight back in the direction it came from, more than Saturn's cloudtops do.

    Uranus is hidden deep in the dawn.

    Neptune (magnitude 7.9, in Aquarius) is very low in the east-southeast just before dawn.


    All descriptions that relate to your horizon — 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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