■ Bright Venus and Jupiter continue their dramatic performance in the western twilight. This evening Venus stands 2° above Jupiter, as shown below (depending slightly on your location). They set about an hour after dark.

Have you ever tried to find Venus or Jupiter in broad daylight, i.e. before sunset? If the air is very clear Venus can be fairly easy to see once your eye lands on the exact spot. Jupiter is much harder, but its closeness to Venus now helps to guide the way. Bring binoculars! And check out "See Jupiter and Venus in Daylight" in the March Sky & Telescope, page 50.

Venus shines close over Jupiter at dusk, March 3, 2023
Venus shines five times brighter than Jupiter. But the surface brightness of Venus's disk in a telescope is nearly 50 times greater than Jupiter's, because Venus is much closer to the illuminating Sun.


■ Venus and Jupiter are now 3° apart in the west in early evening.

■ On the opposite side of the sky in the east, the bright waxing gibbous Moon forms a tall isosceles triangle with Regulus and orange Gamma Leonis (Algieba) under it, as shown below. The Moon is about 13° from each.

Moon crossing Leo, March 4-7, 2023
For the last year, the Moon has formed isosceles triangles (or nearly so) with Regulus and orange Gamma Leonis when it passes them every month. On Sunday evening March 5th, the triangle is so flat that it's nearly a straight line. It will be more triangle-like again on the 6th.


■ Now the Moon, only a day and a half from full, shines between Regulus and Gamma Leonis. Does the moonlight drown out the two stars? Binoculars do the trick. The stars are about 4° and 4½° from the Moon, respectively, less than the width of a typical binocular's field of view.


■ The Moon is full this evening and tomorrow evening. The Moon is exactly full at 7:40 a.m. EST tomorrow morning, midway between the two evenings.

■ The Moon forms another long isosceles triangle with Regulus and Gamma Leonis, this time below them. Again it's about 13° from each.

■ Spot the big, bright, equilateral Winter Triangle in the south during evening this week. Bright Sirius is its bottom point. Betelgeuse is about two fists upper right of Sirius. Procyon is about two fists to Sirius's upper left. The top of the triangle is perfectly level now about one hour after dark.


■ February was Orion's month to stand at his highest in the south in early evening. Now March pushes Orion westward and brings his dog onto the meridian: Canis Major sporting Sirius on his chest.

Want to try for Sirius B, the famous white dwarf? This year Sirius A and B are at their widest apparent separation in their 50-year orbit: 11.3 arcseconds apart. They will remain at essentially this separation for the next few years before they start closing up again. You'll want at least an 8- to 12-inch scope, a night of really, really excellent seeing (keep checking night after night), and Sirius standing at its highest near the meridian (right after dark now). And see the Sirius-B hunting tips in Bob King's article Sirius B – A New Pup in My Life.

Sirius with tiny Sirius B (just above the upper-left diffraction spike).
Sirius with faint Sirius B (just above the upper left diffraction spike). Imaging reduces the 10,000-to-1 brightness contrast between them; Sirius A, actually a pinpoint at the center of the bright blob, is vastly overexposed, meaning that most of its light went unrecorded. Gabriela and Fabio Carvalho took this image in 2017.

The Pup is currently east-northeast of the Dog Star and is 10 magnitudes fainter: one ten-thousandth as bright. Use your very highest power. As Bob recommends, put a homemade occulting bar across your eyepiece's field stop: a tiny strip of aluminum foil held to the field stop by a bit of tape, with one edge crossing the center of the field. Use a pencil point to nudge the edge of the strip into sharp focus as you hold the eyepiece up to a light and look through. In the telescope, rotate the eyepiece to hide blinding Sirius A just behind the strip's east-northeastern edge.

Even with an occulting bar, Sirius B has been undetectable in my 12.5-inch f/6 reflector even at 450x on all but the very, very steadiest nights.

And the farther south you are the better, because Sirius will be higher when it's crossing the meridian. I'm in Massachusetts at 42° north latitude, so. . . no surprise that it's so hard.

Don't worry about moonlight; the glare of Sirius A is much more the problem.


■ It's early March. So quite soon after dark now, the Big Dipper rises as high in the northeast as Cassiopeia has descended to in the northwest. Midway between them, as always, is Polaris.

■ Follow the curve of the Big Dipper's handle down and around, by a little more than a Dipper-length, to find Arcturus, the bright Spring Star. Or the place where it's about to rise. Arcturus comes up fairly soon after dark now, depending on your location.

■ Algol, in Perseus in the northwest, should be at its minimum brightness for a couple hours centered on 9:36 p.m. EST. Algol takes several additional hours to fade and to rebrighten.

After nightfall, the waning gibbous Moon rises in the east near Gamma Virginis on Wednesday the 8th and near Spica on Thursday the 9th. Each Moon-and-star pair crosses the sky for the rest of the night, changing separation and orientation. By the beginning of dawn the following mornings, they're over in the west as shown here.


■ Pollux and Castor in Gemini pass nearly overhead around 8 or 9 p.m. this week if you live in the world's mid-northern latitudes. They go smack overhead as seen from near latitude 30° north: Austin, Houston and the US Gulf Coast, northernmost Africa, Tibet, and Shanghai.


■ Venus and Jupiter continue to move farther apart in the western evening twilight. Tonight finds them 9° from each other, as shown below.

Venus will keep climbing higher in twilight until May, but Jupiter will sink down out of sight before the end of March.


■ Bright Sirius now stands due south on the meridian just as twilight fades into night. Sirius is the bottom star of the equilateral Winter Triangle; the others are orange Betelgeuse to Sirius's upper right (Orion's shoulder) and Procyon to Sirius's upper left. At this time of year, the Winter Triangle balances on Sirius soon after dark.

■ Daylight-saving time begins at 2 a.m. tonight for most of North America. Clocks spring ahead an hour.


■ More about Sirius and Canis Major. In a very dark sky the Big Dog's stick figure is fairly plain to see with the naked eye — the dog is in profile prancing to the right on his hind legs, with Sirius as the shiny dog tag on his chest. The stars of his triangular, pointy-nosed head are dim at 4th magnitude.

For most of us, only his five brightest stars show through our light-polluted skies. These form the unmistakable Meat Cleaver. Sirius and Murzim (to its right) are the wide top end of the Cleaver, with Sirius sparkling on its top back corner. Down to Sirius's lower left is the Cleaver's other end including its short handle, formed by the triangle of Adhara, Wezen, and Aludra. The Cleaver is chopping toward the lower right. Its stubby handle is Canis Major's tail.


This Week's Planet Roundup

Mercury is out of sight in conjunction with the Sun.

Venus and Jupiter shine together in the west at dusk. Venus is the brightest at magnitude –3.9. Jupiter, at magnitude –2.1, is a fifth as bright. Venus is now the upper one, having traded places with Jupiter at their March 1st conjunction.

They get farther apart every day. On Friday March 3rd they's separated by 2°, as shown at the top of this page. By the 10th they widen to 9° apart.

Telescopically, Venus is a shimmering little gibbous ball 12½ arcseconds in diameter and 84% sunlit. Jupiter is 34 arcseconds wide, almost as small as we ever see it; Jupiter is nearly on the other side of the solar system from us now. Moreover, Jupiter is a getting very blurry in a telescope as it sinks to an ever-lower altitude.

But there's an interesting observation that a telescope will still enable. Jupiter displays a strikingly dimmer surface brightness than Venus something you wouldn't guess looking at them with the naked eye. The reason? Jupiter is nearly 7 times farther from the illuminating Sun than Venus is, so its cloudtops are lit nearly 49 times less brightly.

Mars, in Taurus, shines very high toward the south as the stars come out. It shifts southwest, then west and lower, as evening proceeds.

Mars continues to fade, from magnitude +0.4 to +0.5 this week, but it's still a little brighter than Aldebaran (+0.9) some 14° below it. Mars and Aldebaran will match in brightness around the turn of spring (March 20th).

This week, Mars again passes between the horntip stars of Taurus, heading east this time. Watch it change position with respect to them night by night. Mars shines exactly between them on the evening of the 11th, closer to Beta Tauri (to its right) than to dimmer Zeta Tauri (to Mars's left).

In a telescope Mars is now only 8 arcseconds wide. That's too small to show visual details in most telescopes on most nights, aside from its gibbous shape (90% sunlit, see below) and maybe signs of its North Polar Cap.

Gibbous Mars on Feb. 2, 2023
Receding Mars as imaged on February 2nd by Christopher Go in the Philippines. South is up. Upper left of center, the most prominent diagonal dark marking is Mare Sirenum. The North Polar Cap is at bottom. The dark arc just inside the bright limb is partly a processing artifact, but the dark margin of the North Polar Cap is a known real thing.

Saturn is buried deep in the sunrise.

Uranus, magnitude 5.8 in Aries, is high in the west right after dark, way above Venus. See the Uranus finder charts in the November Sky & Telescope, page 49.

Neptune is lost in the sunset.

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 Standard Time (EST) is Universal Time minus 5 hours. Eastern Daylight Time (EDT) is UT minus 4 hours. (UT is also called 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 a more detailed 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 much more 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 all stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo edition
The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown here is the Jumbo Edition, which is in hard covers and enlarged for easier reading outdoors by red flashlight. Sample charts. More about the current editions.

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. 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


Image of misha17


March 3, 2023 at 1:54 pm

As I commented a couple of weeks ago, the Moon passes north of Spica each month but it is slowly approaching closer to the star with passage as the lunar descending node regresses westward.

A series of occultations of Spica begins in 2024, so over the next year we can watch the changes

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Image of Rod


March 5, 2023 at 8:19 pm

I did some stargazing this evening, and some Moon gazing too. 🙂 Observed 1800-1930 EST. Sunset 1803 EST, Full Moon 07-Mar-2023 1240 UT. I enjoyed telescope views of the waxing gibbous Moon and Eta Leonis tonight at 25x. Near 1811 EST, Stellarium 1.2 showed the pair about 17 arcminutes apart, later near 1930 EST about 47 arcminutes apart. Viewing like this shows the Moon's faster orbital velocity in Leo tonight compared to Earth's rotation as the Moon and Eta Leonis rose. Eta Leonis position near the NE quadrant of the Moon’s limb, Mare Crisium visible. I also enjoyed some views of Mars in Taurus at 111x. Nothing special but the planet as a planetary shape and gibbous phase quite distinct near 8 arcsecond angular size. Stellarium 1.2 shows Mars 89.8% illuminated. As I observed, more cirrus clouds moved in near 1930 EST, so I decided to come inside for the evening. I used my 90-mm refractor telescope with TeleVue 40-mm plossl and TeleVue 9-mm Nagler eyepieces. Skies initially mostly clear, then cirrus bands moved in. Temperature 9C, winds NW/5 knots.

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