Nova Cassiopeiae, continued: It's been 11 weeks since Nova Cas 2021 erupted to magnitude 7.7. Surprisingly, it has stayed about that bright ever since except for swelling to 5.3, faint naked-eye visibility, for a week in early-mid May. As of June 7th it was holding at 7.0.

The nova is low-ish in the north-northeast after dark, depending on your latitude. It climbs higher through the night and is very high before dawn. Charts and comparison stars.


■ For much of the spring at our mid-northern latitudes, the Milky Way lies right down out of sight all around the horizon. But watch the east now. The rich Cepheus-Cygnus-Aquila stretch of the Milky Way looms up horizontally across the eastern sky as night advances, earlier and higher each week. A hint for the light-polluted: The Milky Way runs horizontally under Vega, right along the bottom of the Summer Triangle.

Mars stands left of Pollux and Castor this week. On Friday the 4th it's still below the line formed by the two stars, as shown here. It crosses their line on June 7th, then moves farther to their upper left thereafter. Meanwhile, Venus shines at Castor's feet.

■ Make your plans for the eclipse of the Sun Thursday morning June 10th! The eclipse will be annular from sparsely populated northern Ontario through parts of the arctic. But a partial eclipse will occur during and after sunrise if you're northeast of a line from North Carolina through North Dakota. In the US Northeast and eastern Canada, the rising crescent Sun will be spectacular! You will need to scout a spot with a view to the east-northeast horizon. For details, maps, and local timetables, see Joe Rao's article in the June Sky & Telescope, page 34, or the smaller version online.

Europe and most of Russia will see the partially eclipsed Sun high in the middle of the day.


■ Have you ever seen Alpha Centauri? At declination –61° , our brilliant, magnitude-zero neighbor is permanently out of sight if you're north of latitude 29°. But if you're at the latitude of San Antonio, Orlando, or points south, Alpha Cen skims just above your southern true horizon for a little while late these evenings.

When does this happen? When should you look? Just about when Alpha Librae, the lower-right of Libra's two brightest stars, is due south over your landscape. At that time, drop your gaze down from there!


■ The early dawns and bright early mornings of the warm-weather season are a gorgeous time to enjoy the outdoors uncrowded. Habitual slugabeds don't know what they're missing. If you're one of those adventurous few or if you have a crack-of-dawn commute take note: Jupiter and Saturn in early dawn now form a right triangle with Fomalhaut, the out-of-season Autumn Star, way down below. Jupiter is the right angle.


■ Mars, Pollux, and Castor form a straight line this evening. Look fairly low in the west-northwest right after dusk. Mars is the one on the left. By tomorrow, Mars will be very slightly above the line.


■ Here it is just 12 days to summer. But as twilight fades, look very low in the north-northwest for wintry Capella very out of season. The farther north you are, the higher it will appear. You may need binoculars. If you're as far north as Montreal or a Portland (either the one in Oregon or Maine), Capella is actually circumpolar.


■ New Moon and an annular eclipse of the Sun tomorrow morning June 10th! The eclipse will be annular only along a path from northern Ontario across parts of the arctic. But during and after sunrise, a partial eclipse will occur if you're northeast of a line from North Carolina through North Dakota.

In the US Northeast and eastern Canada, the rising crescent Sun will be spectacular! For full details, maps, and local timetables, see Joe Rao's article in the June Sky & Telescope, page 34, or the shorter version online.

Europe and most of Russia will see the partially eclipsed Sun high in the middle of the day Thursday.

Live feed from Gianluca Masi starts at 9:30 UT June 10 (5:30 a.m. EDT).


■ A gigantic asterism you may not know about is the Great Diamond, some 50° tall and extending over five constellations. It now leans in the south to southwest after dusk.

Start with Spica, its bottom. High above Spica is bright Arcturus. Almost as far upper right from Arcturus is fainter Cor Caroli, 3rd magnitude. The same distance down from there is Denebola, the 2nd-magnitude tailtip of Leo. And then back to Spica. Robert H. Baker may have been the first to name the Great Diamond, in his 1954 book When the Stars Come Out.

The bottom three of these stars, the brightest, form a nearly perfect equilateral triangle. The first to name it the "Spring Triangle" was probably Sky & Telescope columnist George Lovi, writing in the March 1974 issue. The name didn't catch on at the time, so let's try again!

■ Can you see the big Coma Berenices star cluster? Does your light pollution really hide it, or do you just not know exactly where to look? It's halfway from Cor Caroli to Denebola.

The cluster's brightest members form an inverted Y. The entire cluster is about 4° wide — a big, dim glow in a fairly dark sky, the size of a ping-pong ball at arm's length. It nearly fills a binocular view.


■ Bright Venus and the thin crescent Moon form a mystic pair low in the west-northwest in twilight, as shown below. They'll be 3° or 4° apart for skywatchers near the US East Coast, and only 2° by the time of twilight for the West Coast. Your best view might be about 40 or 50 minutes after sunset, before they get too low.

The Moon, fresh from eclipsing the Sun when it was new on the 10th, now reappears as a thin, day-and-a-half old crescent near Venus. In the next two days it waxes up past the head stars of Gemini and Mars.


■ The Big Dipper hangs high in the northwest right after dark. The Dipper's Pointers, currently its bottom two stars, point lower right toward Polaris. Above Polaris, and looking very similar to it, is Kochab, the lip of the Little Dipper's bowl.

Kochab stands precisely above Polaris around the end of twilight or a little after. How precisely can you time this event for your location, perhaps using the vertical edge of a building?

■ After dark, look south-southeast for orange Antares, "the Betelgeuse of summer." (Both are 1st-magnitude "red" supergiants). Around and upper right of Antares are the other, whiter stars of upper Scorpius, forming their distinctive pattern. The rest of the Scorpion extends down toward the horizon.

The row of three stars upper right of Antares traditionally marks the Scorpion's head. Notice the middle one, Delta Scorpii. It's obviously brighter than the other two, right? For many years, perhaps ages, it was only a slight trace brighter than the one above it, Beta Scorpii. Then in July 2000 Delta nearly doubled in brightness, changing the whole look of upper Scorpius. And it has stayed bright for most of the years ever since, with fluctuations.

Scorpius as it appears these evenings. For judging the brightness of Delta Sco, Beta is magnitude 2.6 and Antares is 1.1. Delta Sco historically was magnitude 2.3. So far this year it's remained bright at 1.9.

This Week's Planet Roundup

Mercury is out of sight in inferior conjunction with the Sun.

Venus (magnitude –3.8, in lower Gemini) shines low in the west-northwest during twilight. Catch it while you can; it sets before twilight ends.

Mars (magnitude +1.7, in upper Gemini) glows modestly low in the west-northwest right after dark, upper left of Venus and left of Pollux and Castor.

Mars starts the week below the Pollux-Castor line as shown at the top of this page. It crosses the line on June 7th.

Mars is almost as far away as it gets on the far side of its orbit from us. So it's no brighter than even Castor, the fainter of the Pollux-and-Castor "twins." And in a telescope, Mars is just tiny blob 4 arcseconds wide.

Jupiter and Saturn (in dim Aquarius and Capricornus, respectively) rise around 1 a.m. and midnight, respectively (daylight-saving time). By the first glimmer of dawn they're fairly high in the southeast, nearly as high as they will get. Jupiter dominates at magnitude –2.5. Saturn, 18° to Jupiter's right, is a more modest mag +0.5.

Jupiter's Great Red Spot was crossing the planet's central meridian on May 21st when Christopher Go took this stacked-video image centered on 21:09 UT (when the System II central-meridian longitude was 358°). South is up.

Lower right of the Red Spot are two of Jupiter's satellites: dark gray Ganymede and smaller, bright orange Io with its darker polar regions. The black circle lower left of the Red Spot is Io's shadow. (The contrast of this image has been boosted.)

A dark line now nearly encircles the Red Spot Hollow. It looks like a continuation of the two narrow dark bands at left; the whole thing has taken on the "snake head" pattern we've seen before. The Red Spot is the snake's enormous eye. His nose points right (toward celestial east; following).

Don't get too excited; Jupiter shows nowhere near this level of detail visually, especially from latitudes higher than Go's near-equatorial 10° N. For those of us less ideally placed, Jupiter remains moderately low in mediocre telescopic seeing even as dawn begins.

Uranus remains out of sight in the glow of dawn.

Neptune, in Aquarius 21° east of Jupiter, lurks at 8th magnitude low in the east-southeast just before dawn.

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. To become more expert about time systems than 99% of the people you'll ever meet, see our compact article 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



Image of bob kelly

bob kelly

June 4, 2021 at 3:11 pm

Thank you for another great week!
I'll share this on our Westchester Astronomers facebook page.

You must be logged in to post a comment.

Image of misha17


June 4, 2021 at 10:29 pm

Even though the Northern Hemisphere Summer Solstice is still 2 weeks away, the earliest sunrise occurs in the Northern Hemisphere this week. The exact date varies by latitude.

Sunset times continue to occur later each day, compensating for the sunrise change until the solstice, then daily change in sunrise time begins to make the overall daylight hours shorter. Sunset time will continue to occur later each day (with the later sunrise offsetting it) until late June.

You must be logged in to post a comment.

Image of Rod


June 5, 2021 at 6:46 am

mary beth, New Jersey Eclipse Fan. I did get out early this morning and enjoy looking at Jupiter, Saturn and the Moon using my 90-mm refractor telescope and 10x50 binoculars.

[Observed 0400-0515 EDT/0800-0915 UT. Sunrise 0542 EDT/0942 UT. Waning crescent moonrise 0316 EDT/0716 UT. Jupiter’s Great Red Spot crosses central meridian 0840 UT today, 0440 EDT. Ganymede ended a transit at 0738 UT this morning or 0338 EDT. While I viewed Jupiter, Ganymede close to Jupiter's limb. The Great Red Spot visible using #58 Green filter at 71x and 129x views. Various cloud belts visible on Jupiter. Saturn retrograde in Capricornus close to 46 arcminute angular separation from Theta Capricorni star. I could see both in 10x50 binocular views as well as 14-mm view at 71x, and just using my eyeglasses. At 71x, the telescope eyepiece true FOV about 60.48 arcminute. As Saturn continues retrograde, Saturn will slowly move away from Theta Capricorni as it is doing since 23-May when retrograde began. The Cassini division in the rings was visible at 129x views. I could see Titan and Rhea moons at Saturn. The waning crescent Moon was lovely at 71x views with the #58 Green filter Earthshine visible on night side of Moon and distinct with unaided eyes too. Ground fog forming in the pastures and woods. Near 0500, the 17-year cicada were becoming loud in the trees as sunrise approaching. A deer came out into my pasture and snorted displeasure at my presence while viewing this morning.]

You must be logged in to post a comment.

Image of mary beth

mary beth

June 6, 2021 at 11:42 am

Hello @bobkelly, @misha17, Rod, NJEF, Hope everyone’s week is off to a great start! Bob, nice you have an area club. Misha17, I am always following sunrise and sunset times. Here in Houston Texas, our latest yearly sunset occurs at 8:25 PM and that begins four days after the solstice on June 24 goes all the way through July 6.

Rod, you experienced all the best of nature the other night. Nice you could see so much with just your eyes/eyeglasses. I am thinking the deer were afraid you were start eating their cicadas since so much ‘buzz’ lately about humans eating insects!

You must be logged in to post a comment.

Image of New Jersey Eclipse Fan

New Jersey Eclipse Fan

June 7, 2021 at 1:16 am

Great to read these submissions. Thanks, everybody!

You must be logged in to post a comment.

Image of Rod


June 10, 2021 at 8:59 am

mary beth, New Jersey Eclipse Fan, et al. I did observe some of the solar eclipse at sunrise this morning! Great fun, see Bob King report and my notes.
It was an ethereal view at sunrise 🙂

You must be logged in to post a comment.

You must be logged in to post a comment.