This Week’s Sky at a Glance, August 20 – 28

RS Ophiuchi fades. On August eighth the well-known recurrent nova RS Ophiuchi lept from its regular magnitude 11.2 to 4.8, dim naked-eye magnitude, after 15 years of simmering quietude. It’s fading quickly now, as prior to now. See Bob King’s Recurrent Nova RS Ophiuchi Just Blew its Top! with finder charts and comparability stars. Ophiuchus is ideally positioned excessive within the night sky.

Nova Cassiopeiae 2021, in the meantime, has bounced round in brightness ever because it erupted from fifteenth magnitude to 7.7 in March. Among its bumps have been brightenings to magnitude 5.5 in early May and 6.0 round July twenty seventh. As of August twelfth it was all the way down to about 8.5. Cas too is excellently positioned within the night sky. Charts and comparison stars.


■ The Moon shines below Saturn this night, and Jupiter shines to their left, as proven beneath.

Moon under Saturn, then Jupiter, Aug 20 and 21, 2021
As the Moon turns full it hangs below Saturn, then Jupiter which, not coincidentally, are at opposition this month. This scene is in twilight; within the subsequent few hours watch the entire sample climb and switch clockwise.

■ The two brightest stars of summer time are Vega, now overhead shortly after dusk, and Arcturus, shining within the west. Draw a line down from Vega to Arcturus. A 3rd of the way down, the road crosses the dim Keystone of Hercules. Two thirds of the way down it crosses the dim semicircle of Corona Borealis with its one modestly vivid star, Alphecca or Gemma.

Also: Vega and the Keystone star closest to it type an equilateral triangle with Eltanin to their north, the nostril of Draco the Dragon. Eltanin is the brightest star of Draco’s quadrilateral head; he is eyeing Vega.


■ Now the Moon shines below Jupiter, with Saturn to their proper. The Moon is full tonight and tomorrow night time; precise full part happens at 9:02 a.m. tomorrow morning, splitting the date distinction (for night skywatchers within the Americas).

■ As summer time progresses and Arcturus strikes down the western sky, the kite determine of Bootes sprouting up from Arcturus tilts to the proper (relying in your latitude). The kite is slender, barely bent with its high leaning proper, and 23° lengthy: about two fists at arm’s size. Arcturus is its backside level the place the stubby tail is tied on.

The Big Dipper now slants at about the identical peak within the northwest, to the Kite’s proper.


■ The Moon once more varieties a large curving arc with Jupiter and Saturn, however now they’re to the Moon’s proper. The arc spans three fists at arm’s size.


■ By 10 or 11 p.m. the waning Moon is nicely up within the east-southeast. Spot vivid Jupiter off to its higher proper. They type a almost equilateral triangle with Fomalhaut, the Autumn Star, rising beneath Jupiter. How early and low are you able to first see it? Is this your first sighting of Fomalhaut for this year’s apparition?


■ Another signal of the advancing season: Cassiopeia is excessive within the northeast, its W sample tilting up. And beneath it, starry Perseus is reaching up.

The highest a part of Perseus consists of the wintry Double Cluster. To discover it, look beneath the bottom two stars of the Cassiopeia W (they’re the faintest two), by considerably extra that the gap between them. You’re on the lookout for what looks like a small spot of enhanced Milky Way glow. Binoculars or a finderscope will show you how to detect the Double Cluster even by means of a truthful quantity of sunshine air pollution. The pair are a glory in a telescope.


■ As August proceeds and nights start to show chilly, the Great Square of Pegasus looms up within the east, balancing on one nook. Its stars are solely 2nd and third magnitude, and your fist at arm’s size suits inside it.

From the Square’s left nook extends the primary line of the constellation Andromeda: three stars (together with the nook) about as vivid as these forming the Square.

This complete big sample was named “the Andromegasus Dipper” by the late Sky & Telescope columnist George Lovi. It’s formed kind of like a big Little Dipper with an extra-big bowl, and it is at present lifting its contents upward.


■ Low within the northwest or north at the tip of summer time twilights, would you acknowledge noctilucent clouds in case you noticed them? They’re essentially the most astronomical of all cloud varieties, with their excessive altitude and formation on meteoric mud particles. And they’re pretty uncommon — although changing into extra frequent in current years because the ambiance modifications. See Bob King’s article.


■ Whenever vivid Vega crosses nearest your zenith, because it does proper after darkish now, you understand that the Sagittarius Teapot is at its highest due south.

Two hours later when Deneb crosses closest to the zenith, it is the flip of little Delphinus and boat-shaped Capricornus down beneath it to face at their highest due south.

With the passing weeks, Jupiter and Saturn seem ever increased because the stars come out.


■ Now that the Moon is out of the night sky, it is prime Milky Way time. After darkish, the Milky Way runs from Sagittarius within the south, up and a bit left left throughout Aquila and thru the large Summer Triangle excessive overhead, and on down by means of Cassiopeia to Perseus low within the north-northeast.


This Week’s Planet Roundup

Mercury may be very deep within the sundown and fading additional, from magnitude –0.4 to –0.1 this week. You would possibly have a likelihood at it with binoculars or a wide-field scope. About 15 or 20 minutes after sundown, scan for it simply above your west horizon about 18° (almost two fists at arm’s size) decrease proper of Venus. Good luck.

Venus, sensible at magnitude –3.9, shines pure white within the west-southwest throughout twilight. It nonetheless units round twilight’s finish.

Jupiter and Saturn shine within the southeast in late twilight and after darkish. They’re magnitudes –2.9 and +0.2, respectively, in Capricornus.

Jupiter begins the night time lowest. Saturn glows 18° (about two fists) to Jupiter’s higher proper. The pair ranges out round 11 p.m. daylight-saving time. By then they’re about at their highest within the south, at their telescopic greatest.

Saturn reached opposition on August 1st, and Jupiter did so on August nineteenth. So this month they’re at their closest, greatest, and brightest of the year. See “Saturnian Challenges” beginning on web page 52 of the July Sky & Telescope, additionally “Action at Jupiter” within the August issue, web page 50, and “Dog Days with the Gas Giants” on web page 40 of August.

Jupiter’s Great Red Spot aspect, imaged on August seventh by Christopher Go with a 14-inch Schmidt-Cassegrain scope. As is customary for planets that is a stacked-video picture, product of many frames chosen for sharpness after which de-rotated in software program to compensate for the planet’s rotation throughout a lengthy video session. In this picture the colours and distinction are enhanced. South is up.

Note the effective element within the Great Red Spot! The South and North Equatorial Belts have largely diminished to slender dark-reddish strains. Dark red spots proceed simply north of the NEB. Much of the Equatorial Zone continues pale yellow-tan.

Saturn on July 25, 2021
Saturn on July 25. North is up. This beautiful stacked-video picture exhibits element within the broad A Ring, in addition to the skinny Encke Gap simply contained in the outer fringe of the outer B Ring. Saturn’s Equatorial Zone is vivid as typical, and its North Equatorial Belt is distinct. The slender darkish band seemingly on the opposite aspect of the equatorial Zone is definitely the dim, internal C ring. Agapios Elia of Nicosia, Cyprus, took video throughout 45 minutes on July twenty fifth utilizing a 9.25-inch Schmidt-Cassegrain scope. He de-rotated the globe throughout processing after which stacked giant numbers of the of greatest frames.

Uranus (magnitude 5.7, in Aries) and Neptune (magnitude 7.8, at the Aquarius-Pisces border) are excessive within the southeast to south within the early-morning hours.

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 depend 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 grow to be extra knowledgeable about time techniques than 99% of the folks you may ever meet, see our compact article Time and the Amateur Astronomer.

Want to grow to be a higher astronomer? Learn your way across the constellations. They’re the important thing to finding every little thing fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature interest. For an easy-to-use constellation information protecting the entire night sky, use the large month-to-month map within the heart of every situation of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you may want a detailed, large-scale sky atlas (set of charts). The fundamental customary 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 lot of telescopic galaxies, star clusters, and nebulae amongst them. Shown right here is the Jumbo Edition, which is in onerous covers and enlarged for simpler studying outdoor by red flashlight. Sample charts. More about the current editions.

Next up is the bigger and deeper (*20*), plotting stars to magnitude 8.5; almost 3 times as many. The subsequent up, as soon as you understand your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And you’ll want to learn (*28*).

You’ll additionally need a good deep-sky guidebook, similar 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 can be lower than top-quality mechanically, that 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 below the night sky along with your
earbuds in place, hearken 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

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