8th-magnitude Nova in Cassiopeia. Nova Cassiopeiae 2021, now also known as V1405 Cassiopeiae, was holding at about magnitude 7.9 as of March 29th, after it was discovered at 9.6 on March 18th and quickly peaked around 7.7. For finder charts and more info, see Bright Nova Erupts in Cassiopeia. Moonlight is gone from the early-evening sky starting on the 30th.

To get a light curve with the most up-to-date brightness measurements, go to aavso.org and in "Pick a Star", enter "V1405 Cas" and choose "Plot a light curve". There, visual observers' estimates are the open black circles, and photoelectric V magnitudes are the green squares. (You can see calendar dates instead of Julian Days using "Preferences".)

And where's Cassiopeia itself? Catch it sinking in the north-northwest right after the end of twilight. Look early before it gets too low.


■ Now that spring is under way, Orion has taken up his early-spring posture in the southwest during evening. He's tipping westward, and his Belt is turning horizontal as shown below.

Orion in early spring tips toward the right, and his three-star Belt turns horizontal. As always, the Belt points roughly toward orange Aldebaran and the V-shaped Hyades. Akira Fujii
Orion in early spring tips toward the right, and his three-star Belt turns horizontal. As always, the Belt points roughly toward orange Aldebaran and the V-shaped Hyades. Akira Fujii

When does Orion's Belt appear exactly horizontal? That depends on where you live east-west in your time zone, and on your latitude. How well can you time this event? If you're near your time zone's standard longitude, expect it around 8:40 this evening (daylight-saving time). . . more or less.


■ The Moon this evening is less than a day from being exactly full. After dark look far to its lower left, by three or four fists at arm's length, for bright Arcturus, pale yellow-orange, making its way up the eastern sky. By about 9 p.m. daylight-saving time, look two or three fists below the Moon for Spica on the rise.


■ Full Moon (exactly full at 2:48 p.m. EDT). Spica is now about one fist below it come evening. Arcturus is more than twice that far to the Moon's left.


■ This evening Spica shines to the right of the Moon low in the east, by less than a fist at arm's length. Arcturus is three or four times as far to the Moon's upper left.

All week and in fact all April, Jupiter and Saturn edge higher in the southeast during early dawn.


■ We now have an hour of moonless dark sky after the end of twilight (those of us in the world's mid-northern latitudes). This is a good time to check in on Nova Cassiopeiae! See the top of this page.

■ Also while the sky is still dark: Spot the Big Dipper "dumping water" very high in the northeast. The Dipper is the hindquarters and long tail of Ursa Major, the Great Bear.

Nearly crossing the zenith are three pairs of dim naked-eye stars, all 3rd or 4th magnitude, marking the Bear's feet. They're also known as the Three Leaps of the Gazelle, from early Arab lore. They form a long east-west line roughly midway between the Bowl of the Big Dipper and the Sickle of Leo; see the evening constellation chart in the center of the April Sky & Telescope.

According to the Arabian story, the gazelle was drinking at a pond — the big, dim Coma Berenices star cluster — and bounded away when startled by a flick of Leo's nearby tail, Denebola. Leo, however, seems quite unaware of his potential prey at the water hole; he's facing the other way.


■ Castor and Pollux shine together nearly overhead in the south after dark. Pollux is slightly the brighter of these "twins." Draw a line from Castor through Pollux, follow it farther out by a big 26° (about 2½ fist-widths at arm's length), and you're at the dim head of Hydra, the Sea Serpent. In a moonless dark sky it's a subtle but distinctive star grouping, about the width of your thumb at arm's length. Binoculars show it easily through light pollution or moonlight.

Continue the line farther by a fist and a half and you hit 2nd-magnitude Alphard, Hydra's orange heart.

Another way to find Hydra's head: It's almost midway from Procyon to Regulus.

■ The waning gibbous Moon shines in the hours before dawn Thursday morning, in the head of Scorpius now making its late-night appearance. Below or lower left of the Moon you'll find orange Antares.


■ This is the time of year when the dim Little Dipper juts to the right from Polaris (the Little Dipper's handle-end) during late evening. The much brighter Big Dipper curls over high above it, "dumping water" into it. They do the reverse water dump in the fall.


■ Shortly after the end of twilight around this time of year, Arcturus, the bright Spring Star climbing in the east, stands just as high as Sirius, the brighter Winter Star descending in the southwest (for skywatchers at mid-northern latitudes).

These are the two brightest stars in the sky at the time. But Capella is a very close runner-up to Arcturus! Spot it high in the northwest.


■ The huge, bright Winter Hexagon is still in view early after dark, filling the sky to the southwest and west.

Start with brilliant Sirius in the southwest, the Hexagon's lower left corner. High above Sirius is Procyon. From there look higher upper right for Pollux and Castor (lined up nearly horizontal), lower right from Castor to Menkalinan and then bright Capella, lower left from there to Aldebaran (past Mars), lower left to Rigel at the bottom of Orion, and back to Sirius.

The Hexagon is somewhat distended. But if you draw a line through its middle from Capella to Sirius, the "Hexagon" is fairly symmetric with respect to that axis.


This Week's Planet Roundup

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

Mars (magnitude +1.3, in Taurus) shines high in the west after dark. Mars is now visibly fainter than orange Aldebaran below or lower left of it. In a telescope Mars is a mere 5 arcseconds wide: a tiny, shimmering bright blob too small for any surface detail.

Jupiter and Saturn have been slowly emerging into dawn view for the last month. Look for them low in the southeast about 50 or 40 minutes before your local sunrise time. Saturn is the higher of the two, but it's much dimmer at magnitude +0.8. Jupiter shines at magnitude –2.1 (not counting the atmospheric extinction for something so low). Find Jupiter some 12° to Saturn's lower left, roughly a fist at arm's length.

Jupiter is still down low in the dawn, but at Christopher's Go's tropical latitude of just 10° north (Cebu City, Philippines) it stands higher than for those of us at north temperate latitudes. He got this shot on March 26th even through poor seeing and a bright 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 bright blue sky during the image processing, which necessarily degraded the signal-to-noise ratio somewhat.

South here is up. "Oval BA [above center and a bit left] can be seen just after the central meridian. It is still very pale." The South Equatorial Belt "looks very strange," he notes, with its very narrow dark parts and its thin pale center. The Equatorial Zone "has a very strong ochre color" in its central and north parts. "The North Equatorial Belt looks quiet in this region. It also has a very dark color."

Uranus (magnitude 5.8, in western Aries) is sinking away low in the west right after the end of evening twilight.

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, is Universal Time minus 4 hours. Universal Time is also known as UT, UTC, GMT, or Z time. For all the down-and-dirty details see Time and the Amateur Astronomer.

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.

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 sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger (and illustrated) 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."

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



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