Nova Cas takes another brightness bump! Nova Cassiopeiae 2021 erupted to magnitude 7.7 last March. It has stayed mostly about that bright ever since making it a "slow nova" but with a brightness spike to 5.5 in early May and smaller bumps since then. For a while it seemed done for, but as of July 27th UT it had climbed back up to 6.0. Then by the 30th it had dropped to about 7.2. Charts and comparison stars.


■ As summer progresses, Arcturus moves down the western side of the evening sky. Arcturus forms the bottom point of the Kite of Bootes. The Kite, rather narrow, extends upper right from Arcturus by 23°, about two fists at arm's length. The lower right side of the kite is dented inward, as if some celestial intruder once banged into it.


■ On this Saturn-day, Saturn is one day before opposition. Do you notice that Saturn's rings are distinctly brighter, compared to Saturn's globe, than they usually are? This Seeliger effect is caused by the solid ring particles backscattering sunlight to us when the Sun is almost directly behind us. The dusty surfaces of the Moon and Mars do this too, but Saturn's clouds do not. In the case of Saturn the effect is named for Hugo von Seeliger, who studied it in detail and published his findings in 1887.

■ Last-quarter Moon (exact at 9:16 a.m. EDT). By the time the Moon rises late tonight, around midnight or 1 a.m. local daylight saving time, its terminator will be no longer exactly straight but very slightly concave. Look about 15° above the Moon for the brightest stars of Aries, 2nd and 3rd magnitude.

By the very first hint of dawn Sunday morning the Moon will be quite high. Spot the Pleiades to its left, Aldebaran a similar distance below the Pleiades, and the much looser Hyades just above and right of Aldebaran.


Saturn is at opposition, opposite the Sun as seen from Earth. This year Saturn's rings are tilted 18° to our line of sight a lot less than their maximum tilt of 26°, which they displayed from 2016 through 2018, but nowhere near the edge-on aspect they will present in 2025. But their current middling tilt seems (to me anyway) to make Saturn look the most characteristically Saturnlike. (See the pic near the bottom of this page.)

Today is Lammas Day or Lughnasadh, one of the four traditional "cross-quarter" days midway between the solstices and the equinoxes. Sort of. In the many centuries after this tradition took hold in Europe the calendar drifted with respect to the seasons, until our current Gregorian calendar was instituted a few centuries ago to stop such problems. So in 2021, the midpoint between the June solstice and the September equinox actually falls on August 6th, at 5:02 p.m. Eastern Daylight Time (21:02 UT).

That minute is the exact center-balance of astronomical summer: the very top of the circle of the year (as defined by the astronomical seasons, for the Northern Hemisphere.)


■ With the advance of summer the Sagittarius Teapot, in the south after dark now, is tilting and pouring from its spout to the right. The Teapot will tilt farther and farther for the rest of the summer — or for much of the night if you stay out late.

■ Tonight, telescope users can watch Jupiter's moon Europa slowly disappear into eclipse by Jupiter's shadow around 12:29 a.m. EDT. Following behind is Io, which will likewise disappear into Jupiter's shadow around 2:19 a.m. EDT. (Subtract 1 hour from these to get CDT, and so on.)

Earlier in the night, Jupiter's Great Red Spot should cross Jupiter's central meridian around 10:24 p.m. EDT. The spot should be visible almost as easily for about an hour before and after, in a good 4-inch telescope if the atmospheric seeing is sharp and steady. A light blue or green filter helps a bit.

The Red Spot transits about every 9 hours 56 minutes. But not quite like clockwork! It drifts east or west in Jupiter's atmosphere somewhat irregularly. A change often becomes detectable to visual transit timers over a span of some months. Our transit-time predictions are based on fairly recent observations, but don't be surprised if the Red Spot has taken it into its head to move a few minutes off schedule.


Hunting Hebe. The asteroid 6 Hebe is a little past opposition, a pinpoint of about magnitude 8.4 north of the Sagittarius Teaspoon. A pair of 10x50 or larger binoculars, used with care and precision under a dark sky, may be enough for you to pick it out using the finder chart in the July Sky & Telescope, page 50. (The chart there shows Hebe's position for 0:00 UT on the dates indicated, which falls on the evening of the previous date for North America.)


■ If you use a telescope much you're probably familiar with Lyra overhead, harboring Vega, the Double-Double, and the Ring Nebula among other sights. And nearby is Albireo, the beak of Cygnus and one of the sky's finest gold-and-blue double stars.

But between Albireo and Lyra, what about the much-overlooked globular cluster M56? At magnitude 8.3 you might even be able to detect it with large binoculars in a dark sky. To pinpoint the spot, hone in with Matt Wedel's "Lost in Space," his Binocular Highlight column and chart for this lesser-known find in the August Sky & Telescope, page 43.

■ It may be the height of summer, but wintry Gemini is arisen in the east by the time dawn begins. The waning crescent Moon crosses it on Thursday and Friday mornings, August 5th and 6th, as shown below.

Most of the stars of Gemini have faded into the growing light of day by the time sunrise is only 45 minutes away. You'll do better to look earlier when the constellation is lower. If you do get outdoors on the late side, binoculars will help, and the waning Moon provides a reference. (The Moon positions here are, as always, exact for an observer in the middle of North America.)


■ The Big Dipper hangs diagonally in the northwest after dark. From its midpoint, look to the right to find Polaris (not very bright) glimmering due north as always.

Polaris is the end of the Little Dipper's handle. The only other Little Dipper stars that are even moderately bright are the two forming the outer end of its bowl: 2nd-magnitude Kochab and 3rd-magnitude Pherkad. On August evenings you'll find them to Polaris's upper left (by about a fist and a half). They're called the Guardians of the Pole, since they ceaselessly circle around Polaris through the night and through the year.


■ Bright Vega passes closest to overhead around 10 or 11 p.m. now, depending on how far east or west you are in your time zone.

How closely it misses your zenith depends on how far north or south you are. It passes right through your zenith if you're at latitude 39° north (Washington DC, Cincinnati, Kansas City, Lake Tahoe). How closely can you judge this just by looking?

Deneb crosses closest to the zenith two hours after Vega. But to see Deneb exactly straight up you need to be farther north, at latitude 45°: Portland, Minneapolis, Montreal, southern France, northern Italy.


■ Have you been seeing any Perseids meteors yet? For now you'll only see the very occasional Perseid during your observing sessions, but their numbers are gradually increasing. The shower is due to peak late next Wednesday night, August 11, but occasional forerunners begin showing up as much as two or three weeks beforehand. Already the sky is moonlessly dark. For more on this year's Perseids see the August Sky & Telescope, page 48.

It's almost certainly a Perseid around this time of year if, when you trace its path backward far enough across the you find that this line intersects the northern part of Perseus.


This Week's Planet Roundup

Mercury is hidden in conjunction with the Sun.

Venus (bright at magnitude –3.9) shines low due west during twilight. It sets around twilight's end.

Mars is hidden deep in the sunset.

Jupiter (magnitude –2.8, in Aquarius) and Saturn (magnitude +0.2, in Capricornus) shine in the east-southeast after dark. Jupiter starts the night lowest, but it's by far the brighter of the two. Saturn glows yellowly 19° (about two fists at arm's length) to Jupiter's upper right. The pair levels out around midnight, depending on your date and location. By then they're nearly at their highest in the south, at their telescopic best.

Saturn reaches opposition on August 1st, Jupiter on August 19th, so they're already essentially as close and big as they'll get this year. See "Saturnian Challenges" starting on page 52 of the July Sky & Telescope, also "Action at Jupiter" in the August issue, page 50, and "Dog Days with the Gas Giants" on page 49 of August.

Jupiter on July 12, 2021
Jupiter on July 12th, imaged by Christopher Go. South is up. The South and North Equatorial Belts have mostly diminished to narrow darkish lines. Red barges and spots continue just north of the NEB. Much of the Equatorial Zone continues pale yellow-tan. The Great Red Spot is on the other side of Jupiter, but note the row of white ovals in the south temperate area.
Saturn on July 25, 2021
Saturn on July 25. North is up. This exquisite stacked-video image shows detail in the broad A Ring, as well as the thin Encke Gap just inside the outer edge of the outer B Ring. Agapios Elia of Nicosia, Cyprus, took video across 45 minutes on July 25, 2021, using a 9.25-inch Schmidt-Cassegrain scope. He de-rotated the globe in processing and stacking large numbers of the of best frames.

Uranus (magnitude 5.7, in Aries) is high in the east-southeast before dawn begins.

Neptune (magnitude 7.8, at the Aquarius-Pisces border 23° east of Jupiter) crosses high in the south in the early-morning hours.

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 mary beth

mary beth

July 30, 2021 at 10:39 am

Timely history: On this day in 1610, Italian astronomer Galileo Galilei was first to observe what we now know are Saturn’s rings.

Will be thinking of him while watching the opposition. Imagine his astonishment!! As many times as I have seen Saturn in pictures and a few times in a telescope, I still marvel!

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Anthony Barreiro

July 30, 2021 at 3:53 pm

But Galileo didn't have enough magnification to see the rings as rings. He thought Saturn had ears!

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mary beth

July 30, 2021 at 5:20 pm


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Anthony Barreiro

July 30, 2021 at 3:52 pm

The exquisite stacked video image of Saturn shows the blue color of the south polar region. I just read Thomas Dobbins' article about this phenomenon in the September Sky and Telescope. It's winter in Saturn's southern hemisphere. Less sunlight creates less photochemical smog. The clearer atmosphere allows more scattering of sunlight, so the sky is blue, just like here on Earth.

It's encouraging to see the blue so clearly in a recent photo. I'm hoping to see this through my four inch refractor when the weather and logistics cooperate. Hopefully a yellow, orange, or light red filter will help. If my little refractor doesn't gather enough light, I'll hope for a view through the bigger scopes of friends in my astronomy club at our star party next weekend.

Mary Beth, I hope you will have plenty more opportunities to see Saturn through a telescope!

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mary beth

July 30, 2021 at 5:21 pm

Thank you Anthony and I certainly hope you can get some real dark skies for viewing. I guess your astronomy club meets somewhere out of the city? looking forward to your report!

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New Jersey Eclipse Fan

July 30, 2021 at 5:36 pm

As usual, I enjoyed the back-and-forth regarding Saturn. When I read Mary Beth's first comment, I thought to myself, Wasn't Galileo the guy who thought the rings were ears? Then I read Anthony's reply, which was verification enough for me. Wait a sec--you mean Saturn's rings go all the way back to 1610? 😉

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mary beth

July 31, 2021 at 11:15 am

According to Wikipedia (lol), 1610 was also the year that Jupiter’s moons were discovered, and the gorgeous Orion Nebula was I assume Saturn did NOT want to be outdone!! Good thinking on his part!

On a side note, Monteverdi published the Vespers of 1610 which to this date is still considered to be the most beautiful piece of sacred music!! And Henry Hudson discovered the Northwest Passage!! Banner Year!!

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mary beth

July 31, 2021 at 11:16 am

Hudson Bay that is!

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July 31, 2021 at 8:35 am

Well, some lively comments by mary beth, Anthony, and New Jersey Eclipse Fan. Good to see other folks enjoying Jupiter and Saturn and the night sky in general, also the astronomical history lesson :). Yesterday I spent more time splitting logs and stacking the wood for later use. I was thinking about viewing Jupiter and Saturn last night in Maryland, the skies were better and clearer but after all that hard work out in the pasture, I kicked back in my comfy sofa, relaxed, watched some tv and netflix, no stargazing or observing 🙂

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Yaron Sheffer

July 31, 2021 at 9:40 am

Dang...that Saturn pic is a beaut. Perfectly representing how I saw it many years ago through a sturdy 6-inch refractor.

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August 2, 2021 at 7:52 am

mary beth et al. I did some Saturn opposition early this morning or maybe opposition 🙂 I used my 90-mm refractor telescope. [Observed 0030-0130 EDT/0430-0530 UT. Saturn retrograde motion places it about 4 degrees west of Theta Capricorni star now. I was able to view Saturn early this morning using 9-mm eyepiece at 111x views and no filters. Saturn transit my location near 0114 EDT/0514 UT. Saturn rings with Cassini division visible, some cloud bands apparent on Saturn, and the moons Titan and Rhea visible too in the FOV. True FOV about 44 arcminutes. Titan about mv + 8.46 and Rhea about mv + 9.84. There were two 10th-11th magnitude stars visible in the FOV along with some others. TYC6348-1189-1 was visible in the FOV, mv + 11.15 and TYC6348-1439-1 visible in the FOV too, mv + 9.68. Both stars about 10 to 12 arcminutes angular separation from Saturn. TYC6348-1439-1, SIMBAD portal shows mv + 9.69 and stellar parallax 0.9279 mas. SIMBAD shows designator HD 198447 too for this star. The parallax places the star some 3500 light years distance or a bit farther. Near 0100 EDT I observed a bright meteor flash by moving away from Aquarius near Jupiter position, traveling north. It was about as bright as Saturn. Aquarids are visible so likely an Aquarids. Aquarids move about 40 km/s or so. Observing was better but rain earlier and very humid with trees dripping rain on the ground. Some great horn owls were out hooting in the woods. An enjoyable Saturn opposition time with a possible Aquarid meteor observed. In Delphinus, I could see Zeta Delphini star near mv + 4.62, some 5th magnitude stars visible despite rain earlier and humidity while viewing. Some altocumulus clouds rolled in after 0100 EDT. Temperature 20C and NE winds 3 knots.]

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mary beth

August 3, 2021 at 4:14 pm

Hello Rod! Sounds like despite the unsettled weather you were able to get some real good viewing! Quite nice that the meteor streaked by, what a treat! Saturn was definitely noticeably brighter here on Sunday night, on Monday I was not able to view because of clouds. We should have a clear weekend so that’s probably my next chance to really see anything except through broken clouds. I felt like Antares and the stars in the head of the scorpion are brighter than usual but that was probably only due to the fact there was no moon and the are right at the Meridian at dark, so very fine viewing.

Hope we hear from some others who got to see Saturn’s opposition. Maybe Anthony will give us a report from his club’s gathering!

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