This Week’s Sky at a Glance, April 2 – 10

Eighth-magnitude Nova in Cassiopeia. Nova Cassiopeiae 2021, now also referred to as V1405 Cassiopeiae, was nonetheless at about magnitude 8.2 as of April 2nd, after it was found at 9.6 on March 18th and shortly peaked at 7.7. For finder charts and extra data, see Bright Nova Erupts in Cassiopeia.

To get a gentle curve with essentially the most up-to-date brightness measurements, go to and in “Pick a Star”, enter “V1405 Cas” and select “Plot a light curve”. There, visible observers’ estimates are the open black circles, and photoelectric V magnitudes are the green squares. (You can see calendar dates as an alternative of Julian Days utilizing “Preferences”.)

And the place’s Cassiopeia itself? Catch it sinking within the north-northwest proper after the top of twilight. Look early earlier than it will get too low!


■ Shortly after the top of twilight round this time of year, Arcturus, the brilliant Spring Star climbing within the east, stands simply as excessive as Sirius, the brighter Winter Star descending within the southwest (for skywatchers at mid-northern latitudes).

These are the 2 brightest stars within the sky at the time. But Capella is a very shut runner-up to Arcturus! Spot it excessive within the northwest.

Jupiter and Saturn edge ever increased within the southeast throughout early daybreak all April. . .


■ The enormous, vivid Winter Hexagon continues to be in view early after darkish, filling the sky to the southwest and west.

Start with sensible Sirius within the southwest, the Hexagon’s decrease left nook. High above Sirius is Procyon. From there look increased higher proper for Pollux and Castor (lined up almost horizontal), decrease proper from Castor to Menkalinan after which vivid Capella, decrease left from there to Aldebaran (previous Mars), decrease left to Rigel at the underside of Orion, and again to Sirius.

The Hexagon is considerably distended. But in the event you draw a line via its center from Capella to Sirius, the “Hexagon” is pretty symmetric with respect to that axis.

■ Last-quarter Moon tonight (precisely final quarter at 6:02 a.m. Sunday morning EDT). The Moon rises tonight very late, round 2 or 3 a.m. Before daybreak on Sunday morning the you will discover it shining at the deal with of the Sagittarius Teapot.


■ Right after it is totally darkish, Sirius shines brilliantly within the south-southwest. Lower left of Sirius, by about one fist, is the triangle of Adhara, Wezen, and Aludra, from proper to left. They type Canis Major’s hind foot, rear finish, and tail, respectively. Or, alternatively, the decrease finish and deal with of the Meat Cleaver.

Slightly higher left of them, forming a Third- and 4th-magnitude arc 7° lengthy, are the three uppermost stars of the constellation Puppis. No, that is not a pet, regardless of following proper behind the Big Dog. It’s the Poop Deck (stern) of the large historical constellation Argo Navis, the ship of Jason and the Argonauts. These three are the one stars of Argo which are readily seen naked-eye from mid-northern latitudes.

Just 1.5° higher proper of the center of the three, binoculars on a darkish evening will present the Sixth-magnitude open cluster M93. It’s elongated northeast-southwest.


■ Shortly after the top of twilight round this time of year, Arcturus, the brilliant Spring Star climbing within the east, stands simply as excessive as Sirius, the brighter Winter Star descending within the southwest (for skywatchers at mid-northern latitudes).

■ Early in Tuesday’s daybreak the crescent Moon shines beneath Saturn, as proven under. Then in Wednesday’s daybreak, the Moon shines beneath Jupiter.

. . .And on April Sixth and seventh, the waning Moon poses beneath the large planets.


■ The vivid star excessive within the west-northwest throughout and after nightfall is Capella. Its pale-yellow colour matches that of the Sun, which means they’re each about the identical temperature. But in any other case Capella may be very completely different. It consists of two yellow-giant stars orbiting one another each 104 days.

Moreover, for telescope customers, it is accompanied by a distant, tight pair of red dwarfs: Capella H and L, magnitudes 10 and 13. Article and finder charts.


■ Castor and Pollux shine collectively almost overhead within the south after darkish. Pollux is barely the brighter of those “twins.” Draw a line from Castor via Pollux, observe it farther out by a large 26° (about 2½ fists at arm’s size), and also you’re at the dim head of Hydra, the Sea Serpent. In a moonless darkish sky it is a refined however distinctive star grouping, in regards to the width of your thumb at arm’s size. Binoculars present it simply via gentle air pollution or moonlight.

Continue the road farther by a fist and a half and also you hit 2nd-magnitude Alphard, Hydra’s orange coronary heart.

Another way to search out Hydra’s head: It’s nearly halfway from Procyon to Regulus.


■ At this time of year, the 2 Dog Stars stand vertically aligned across the finish of twilight. Look southwest. Brilliant Sirius in Canis Major is under, and Procyon in Canis Minor is excessive above.


■ Vega, the brilliant “Summer Star,” rises within the northeast late these evenings. Exactly the place do you have to look ahead to it to come back up? Spot the Big Dipper nearly overhead within the northeast. Look at Mizar at the bend of its deal with. If you’ll be able to see Mizar’s tiny, shut companion Alcor (binoculars present it simply), observe a line from Mizar via Alcor all of the way all the way down to the horizon. That’s the place Vega will make its look.


■ By late night the Sickle of Leo stands almost vertical excessive within the south. Its backside star is Regulus, the brightest of Leo. Leo himself is strolling westward. The Sickle types his entrance leg, chest, mane, and a part of his head. Off to the left, a lengthy proper triangle types his hind finish and lengthy tail.


This Week’s Planet Roundup

Mercury, Venus, and Neptune are out of sight within the glare of the Sun.

Mars (magnitude +1.3, in Taurus) shines excessive within the west after darkish. It’s visibly fainter now than than orange Aldebaran under it, to not point out brighter orange Betelgeuse farther to Mars’s left. In a telescope Mars is a mere 5 arcseconds vast: a tiny, shimmering vivid blob too small for any floor element.

Jupiter and Saturn have been rising into daybreak view for the final month. Look for them low within the southeast about 60 to 40 minutes earlier than your native dawn time. Saturn is the upper of the 2, nevertheless it’s a lot dimmer at magnitude +0.8. Jupiter shines at magnitude –2.1 (these values do not depend the atmospheric extinction for objects at low altitudes). Find Jupiter some 12° to Saturn’s decrease left: roughly a fist at arm’s size.

Jupiter continues to be down low within the daybreak, however at Christopher’s Go‘s tropical latitude of simply 10° north (Cebu City, Philippines) it stands increased than for these of us at north temperate latitudes. He bought this shot on March twenty sixth even via poor seeing and a vivid sky. “Here are my first images of Jupiter for this season,” he writes. “Jupiter was only 25 deg above the horizon. It was almost sunrise.” He subtracted out the brilliant blue-sky foreground in the course of the picture processing, which essentially degraded the signal-to-noise ratio considerably.

South right here is up, celestial west is left. “Oval BA [well above center and a bit left] can be seen just after the central meridian. It is still very pale,” he notes. The South Equatorial Belt “looks very strange” with its very slender darkish traces and skinny pale heart. The Equatorial Zone “has a very strong ochre color” in its central and north components. “The North Equatorial Belt has a very dark color.”

Uranus (magnitude 5.8, in western Aries) units within the west simply after the top of night twilight.

All descriptions that relate to your horizon — together with the phrases up, down, proper, and left — are written for the world’s mid-northern latitudes. Descriptions that additionally rely upon longitude (primarily Moon positions) are for North America.

Eastern Daylight Time, EDT, is Universal Time minus 4 hours. Universal Time is also referred to as UT, UTC, GMT, or Z time. To turn into extra skilled about time techniques than 99% of the folks you will ever meet, see our article Time and the Amateur Astronomer.

Want to turn into a higher astronomer? Learn your way across the constellations. They’re the important thing to finding all the things fainter and deeper to hunt with binoculars or a telescope.

This is an outside nature pastime. For an easy-to-use constellation information masking the entire night sky, use the large month-to-month map within the heart of every challenge of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you will want a detailed, large-scale sky atlas (set of charts). The primary commonplace is the Pocket Sky Atlas (in both the original or Jumbo Edition), which exhibits stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo edition
The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and a whole bunch of telescopic galaxies, star clusters, and nebulae amongst them. Shown right here is the Jumbo Edition, which is in exhausting covers and enlarged for simpler studying outdoor by red flashlight. Sample charts. More about the current editions.

Next up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; almost 3 times as many. The subsequent up, as soon as you recognize your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And make sure you learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, corresponding to Sky Atlas 2000.0 Companion by Strong and Sinnott, or the larger (and illustrated) Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope exchange charts? Not for freshmen, I do not suppose, and never on mounts and tripods which are lower than top-quality mechanically, which means heavy and costly. And as Terence Dickinson and Alan Dyer say of 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 beneath the night sky along with your
earbuds in place, take heed to Kelly Beatty’s month-to-month
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

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart