FRIDAY, APRIL 8
■ The first-quarter Moon this evening forms a tall, nearly isosceles triangle with Pollux and Castor above it: the two top stars of the Arch of Spring. The Moon is about 8° from each. The stars are 4½° apart.
The rest of the Arch of Spring consists of Procyon, shining lower left of Pollux and Castor, and Menkalinan and then bright Capella farther to the twins' lower right.
■ Over and done are the planetary triangles and bunchings that have highlighted the early dawn. Venus, Mars, and Saturn now form an expanding diagonal line, as shown below. From now on this line will just get longer and longer.
SATURDAY, APRIL 9
■ Now the Moon shines left or upper left of Pollux and Castor in the evening.
■ Seen soon after dark this week, Orion tilts in the southwest in his spring orientation: striding down to the right, with his belt horizontal. The belt points left toward Sirius and right toward Aldebaran and, farther on, the Pleiades.
SUNDAY, APRIL 10
■ Sirius, Procyon, the Moon, and the Pollux-Castor pair form an enormous Y in the sky. Face southwest. Brilliant Sirius is the Y's bottom. Procyon is its middle. The Moon marks the tip of its left branch, and Pollux and Castor give a flourish to the end of its right branch.
MONDAY, APRIL 11
■ The Sickle of Leo hooks around the waxing gibbous Moon this evening. The Sickle is standing upright with its open side to the right. Its brightest stars are Regulus below or lower left of the Moon soon after dark (for North America), and Gamma Leonis (Algieba) the same distance left of the Moon.
You'll need clear air to see the fainter stars of the Sickle well through the Moon's bright light. As always, binoculars help.
TUESDAY, APRIL 12
■ Now the gibbous Moon forms an equilateral triangle with Regulus and Algieba (for North America), 8° on a side.
Twice as far to the Moon's lower left is Denebola, Leo's tail-tip.
■ At this time of year, the two Dog Stars stand vertically aligned around the end of twilight. Look southwest. Brilliant Sirius in Canis Major is below, and Procyon in Canis Minor is high above it.
WEDNESDAY, APRIL 13
■ The Moon continues its eastward advance. Denebola is now closer to its upper left, and the Sickle has been left far behind.
Look three or four fists lower left of the Moon for Spica, and three fists upper left from Spica for brighter Arcturus.
■ While Arcturus is climbing high in the east, equally bright Capella is descending high in the northwest. They stand at exactly the same height above your horizon at some moment between about 9:00 and 10:30 p.m. daylight-saving time, depending mostly on how far east or west you live in your time zone.
How accurately can you time this event for your location? Like everything constellation-related, you'll find that it happens 4 minutes earlier each night.
THURSDAY, APRIL 14
■ Capella, high in the northwest during and after dusk, has a pale yellow color matching the Sun's, which means they're about the same temperature. But otherwise Capella is very different. It consists of two yellow giant stars orbiting each other every 104 days.
Moreover, for telescope users, it's accompanied by a distant, tight pair of red dwarfs: Capella H and L, magnitudes 10 and 13. That's about 10,000 and 60,000 times fainter than Capella itself! Article and finder charts. Can you make out at least H with your scope through the moonlight?
FRIDAY, APRIL 15
■ This evening the Moon is only about 3/4 of a day from full (for evening in North America). Look below it for Spica. Much farther to the Moon's left is brighter Arcturus.
SATURDAY, APRIL 16
■ Full Moon (exactly full at 2:55 p.m. EDT). At nightfall, the Moon is in the dim feet of Virgo. Spica shines about 9° to its upper right (nearly a fist at arm's length), perhaps struggling to be seen through the moonlight. Brighter Arcturus is some 30° to the Moon's upper left.
This Week's Planet Roundup
Mercury, after last week's conjunction with the Sun, creeps up into the low afterglow of sunset late this week. By about Thursday the 14th, look for it low above the west-northwest horizon 30 or 40 minutes after sunset. At least it's bright, magnitude –1.2 that evening. Binoculars will help. With binoculars you may start to pick it up a few days earlier.
Venus, magnitude –4.4, is the bright "Morning Star" shining low in the southeast during dawn.
Mars and Saturn glimmer to Venus's upper right, in that order. They're vastly fainter: almost identical at magnitudes +1.1 and +0.9. Mars, however, is more orange than pale yellow Saturn. Each morning they're a little farther from Venus and from each other.
Jupiter emerges into dawn view this week, well to the lower left of Venus. On the morning of April 9th, it's 19° from Venus. By April 16th they close to within 13° of each other. Look for Jupiter about 45 to 30 minutes before sunrise.
Uranus is lost in the sunset.
Neptune remains invisible in the sunrise glow, close to Jupiter but only magnitude 7.9.
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 and graphics that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time, EDT, is Universal Time minus 4 hours. (Universal Time is also called UT, UTC, GMT or Z time.)
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. 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.
Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And be sure to read How to Use a Star Chart with a Telescope. (It applies just as much to charts on your phone or tablet as to charts on paper.)
You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.
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, meaning heavy and expensive. And 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."
Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the heavens above. It's free.
"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996
"Facts are stubborn things."
— John Adams, 1770