Moon under Leo, March 9-12, 2017
As the Moon waxes though full, it shines under Leo. As always, for clarity, the Moon is shown here three times its actual apparent size.

Friday, March 10

• The bright Moon hangs a few degrees below or lower left of Regulus this evening, as shown here. The Sickle of Leo extends from Regulus toward the upper left.

• Late tonight comes the second-brightest asteroid occultation predicted this year for North America. A 6.3-magnitude star in Leo’s snout, just in front of the Sickle, should snap out of sight for up to 3 seconds for observers along a narrow track running from the Georgia coast to just north of San Francisco. The culprit is the 15th-magnitude asteroid 1343 Nicole, only about 26 km (16 miles) wide.

Leo will be very high in the southwest or south at the time. For times, detailed maps, a finder chart for the star (easily spotted less than 1° northeast of Lambda Leonis), and other information, see Steve Preston's prediction pages for this event.

Saturday, March 11

• The Moon is equally full this evening and tomorrow evening, as seen from the longitude of the Americas. That's because the exact time of full Moon, 10:54 a.m. March 12th EDT, lands halfway between the two evenings. This evening the Moon shines by the dim hind leg of Leo (too dim to be plotted above). Tomorrow evening it's by the dim head of Virgo.

• Daylight-saving time begins at 2 a.m. Sunday morning for most of North America. Clocks spring forward.

Sunday, March 12

• As the stars come out this week, Sirius shines high in the south. Sirius is the bottom star of the bright, equilateral Winter Triangle. The Triangle's other two stars are orange Betelgeuse to Sirius's upper right (Orion's shoulder) and Procyon to Sirius's upper left.

Monday, March 13

• The Moon rises due east around the end of twilight. Almost an hour later Jupiter follows up below it, and about 20 minutes later Spica rises to Jupiter's lower right. This curving vertical lineup is high in fine view by about 9:30 or 10.

Tuesday, March 14

• Jupiter, Spica, and the waning gibbous Moon form a triangle that rises in the east around 9 or 10 p.m. tonight.

• Algol shines at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for roughly two hours centered on 9:24 p.m. Pacific Daylight Time.

Wednesday, March 15

• The tiny black shadow of Jupiter's moon Europa crosses the planet's face tonight from 10:48 p.m. to 1:17 a.m. EDT, with Europa itself following behind from 11:55 p.m. to 2:16 a.m. EDT. Subtract 1 hour from these times to get CDT, 2 hours to get MDT, 3 hours to get PDT.

Thursday, March 16

• We've entered the time of year when Orion declines in the southwest after dark, with his Belt turning horizontal. But when does Orion's Belt appear exactly horizontal? That depends on where you're located east-west in your time zone, and on your latitude.

Can you time this event? If you're near your time zone's standard longitude, expect it around 9:10 this evening. . . more or less.

Friday, March 17

• On the traditional divide between the winter and spring sky is the dim constellation Cancer. It lies between Gemini to its west and Leo to its east. Dim it may be, but Cancer holds something unique: the Beehive Star Cluster, M44, in its middle. The Beehive shows dimly to the naked eye if you have little or no light pollution. With binoculars, it's a snap even from fairly polluted areas. Look for it a little less than halfway from Pollux in Gemini to Regulus in Leo.

• Algol is at minimum light for about two hours centered on 9:14 p.m. Eastern Daylight Time.

Saturday, March 18

• Jupiter's moon Io, barely off Jupiter's western limb, disappears into eclipse by Jupiter's shadow around 10:24 p.m. EDT. A small telescope will show it slowly fade away.


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 guide to astronomy.

Pocket Sky Atlas, jumbo edition
The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae. Shown above is the new Jumbo Edition for easier reading in the night. Click image for larger view.

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, is 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, or the bigger Night Sky Observer's Guide 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."

This Week's Planet Roundup

Venus waning
Raffaello Lena in Rome has been imaging Venus as it wanes in phase and enlarges in size, using a 7-inch Maksutov-Cassegrain scope. He plans to continue right up to Venus's conjunction 8° north of the Sun.
Jupiter on Feb. 25, 2017
Jupiter on February 25th, with two red spots: the Great Red Spot and Oval BA ("Red Spot Junior"), which is drawing increasingly far away to the GRS's preceding (celestial west) side. The small dark patch that was in the north part of the GRS two days earlier is gone; the spot's deep-red center remains. North is up. Note the darkness of the North Equatorial Belt compared to its south equivalent, and the white outbreak occurring in the NEB at the central meridian. Damian Peach in the UK took this image remotely with the 1-meter Chilescope.
Saturn on Feb. 26, 2017
Saturn on February 26th, remotely imaged by Damian Peach with the 1-meter Chilescope. South is up. "Seeing was good (though not excellent)," he writes, "but large aperture on Saturn really seems to work wonders. The [North Polar] Hexagon is nicely seen. Also note that the Encke Gap is seen around the whole of Ring A."
Mercury is begins to emerge low in the afterglow of sunset at the end of this week. By March 17th, use binoculars about 20 minutes after sunset to look for it about 10° lower left of much brighter Venus.

Venus (magnitude –4.4) is dropping fast day be day in the western evening twilight. It's swinging toward our line of sight to the Sun, making it an ever thinner crescent in a telescope or even high-quality binoculars. It's now a big 55 arcseconds or so from cusp to cusp, and from March 10th to 17th its phase things from 8% to just 3% sunlit.

Get your scope on Venus before sunset — while keeping the Sun behind a western horizon obstruction so you don't accidentally sweep across the Sun's blinding face. Can you detect any sign of cusp extensions around Venus's rim? See the March Sky & Telescope, page 52.

Venus will continue to sink, expand, and wane in phase until inferior conjunction on March 25th, when it will pass a full 8° north of the Sun. For Northern Hemisphere observers, this is the ideal apparition for following Venus way down in the west right after sunset — and picking it up very low in the east before dawn. In fact, plan to look for it at both dusk and dawn on the same day, or across the same night! Your best bet for this rare dual sighting of Venus is on March 22nd, as told in the March Sky & Telescope, page 46.

There you'll also find a tip for detecting the crescent of Venus naked-eye when it's as large as it is now, by sighting through a tiny round hole in a piece of paper or cardboard held against your eye to mask off aberrations in the outer part of your eye's pupil. Experiment with different size holes.

Mars (magnitude +1.4, in Aries) is the faint orange "star" well to the upper left of Venus, by 20° to 26° this week. In a telescope Mars is just a tiny fuzzblob 4.5 arcseconds across.

Mars is traveling eastward against the stars almost as fast as the seasonal turning of the sky carries the stars westward above your local landscape (as seen at the same time each evening). So even as Venus plummets, Mars will continue to hang almost in place from night to night.

Jupiter (magnitude –2.4, in Virgo) rises around not long after dark and shines high in the east by 11 p.m. Spica dangles 4° or 5° lower right of it after they rise, more directly below it around the middle of the night, and lower left of it in early dawn. By then they've moved over and down to the southwest.

In a telescope Jupiter is about 44 arcseconds across its equator, essentially as big as it will appear even around its April 7th opposition.

Saturn (magnitude +0.5, at the Ophiuchus-Sagittarius border) rises in the early morning hours and glows in the south-southeast before and during dawn. Redder Antares (magnitude +1.0) twinkles 18° to its right.

Uranus is sinking down in the west at nightfall, between Mars and Venus.

Neptune is hidden deep in the glow of sunrise.


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 Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 hours. Eastern Daylight Time (EDT) is UT minus 4 hours.


"This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours."
— Neil deGrasse Tyson, 2014

"Objective reality exists. Facts are often determinable. Vaccines stop diseases. Carbon dioxide holds in global warmth. Science and reason are no political conspiracy; they are how we discover objective reality. Civilization's survival depends on our ability, and willingness, to do so."
— Alan MacRobert, your Sky at a Glance editor

"Facts are stubborn things."
— John Adams, 1770

Stand against falsehoods, denialism, and suppression of research. March For Science on April 22nd, to “champion publicly funded and publicly communicated science as a pillar of human freedom and prosperity.”



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March 11, 2017 at 10:35 am

I've been watching Venus for several months with a 70mm refractor. I just bought (3 months ago) a 130mm reflector and I love the view of Venus at 144x . I've looked at Venus quite a lot in my 60 years, I've owned 4 telescopes(3 of them small refractors) But I've never followed it all the way to inferior conjunction. If the weather holds out, I will this time.

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March 15, 2017 at 1:10 pm


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