This Week’s Sky at a Glance, October 15 – 23

We cannot look away. Long-lasting, ever fluctuating Nova Cassiopeiae 2021 was lastly right down to about magnitude 8.2 as of October 14th. That’s nonetheless barely fainter than when it exploded final March. Charts and comparison stars.

The gibbous Moon lingers with Jupiter on Friday night the fifteenth, earlier than transferring ever eastward to show full on the twentieth beneath the Great Square of Pegasus.


■ Bright Jupiter and fainter Saturn proceed to dominate the southern night sky from their residence in dim Capricornus, as proven above. They stay 15° aside; each are practically stationary at the west finish of their retrograde loops.

■ Spot Venus low within the west in twilight. Just decrease left of it, by 1½° (about a finger’s width at arm’s size), search for orange Antares, lower than 1% as shiny. Venus stays about this near Antares for the subsequent two days, however watch their orientation change.


■ It’s International Observe the Moon Night, with greater than 1,960 occasions worldwide inviting you to indicate up! Or, put on your own event and add it to the map. All it’s good to host a Moon-observing occasion is a telescope, a place to place it, and a readiness to welcome guests for a look. Or you’ll be able to simply invite family and friends, and it nonetheless counts.

The Moon is waxing gibbous. Its terminator crosses Oceanus Procellarum, which exhibits off the dramatic crater Copernicus and numerous different options.

To the bare eye, the Moon varieties a roughly equilateral triangle with shiny Jupiter to its proper or higher proper, and Fomalhaut to the Moon’s decrease proper.

Cloudy the place you’re? Gianluca Masi of the Virtual Telescope Project plans a narrated live feed of the Moon from Rome, beginning at 17:30 UT (3:30 p.m. EDT).


■ This is the time of year when, in early night, W-shaped Cassiopeia stands on finish excessive within the north-northeast — and when, decrease left of Cas within the north, the dim Little Dipper extends leftward from Polaris.

Below or decrease proper of Cassiopeia is star-scattered Perseus. Look decrease left from Perseus, or far under Cas, for shiny (zero-magnitude) Capella.


■ Vega is the brightest star very excessive west of the zenith after darkish. Less excessive within the south-southwest is Altair, not fairly as shiny. Still close to the zenith is the third and least shiny star of the Summer Triangle, Deneb.

Look decrease left from Altair by three or 4 fists at arm’s size, and also you hit can’t-miss-it Jupiter. Extend that line two fists farther on, and also you hit Fomalhaut.


■ Look two fists left of the good Moon this night for the brightest stars of Aries, not far aside. Through the moonlight, are you able to see one in every of them, or two, or three? Hamal is magnitude 2.0. Sheratan to its proper or higher proper is is magazine 2.6. Mesarthim, nearer to the decrease proper of Sheratan, is tougher at magazine 3.9. Averted imaginative and prescient helps.


■ Full Moon (precisely so at 10:57 a.m. EDT). The Moon rises within the east about 20 minutes after sundown for the mid-latitudes of North America. Right after darkish, look three fists above the Moon for Alpheratz, the 2nd-magnitude head of Andromeda and the leftmost nook of the Great Square of Pegasus.

■ It’s a busy night at Jupiter. At 8:41 p.m. EDT the tiny black shadow of Io begins crossing Jupiter’s face, getting into on the east limb, adopted by Io itself about an hour later. The shadow leaves Jupiter’s western limb at 10:58 p.m. EDT, adopted by Io an hour after that.

Meanwhile, Jupiter’s Great Red Spot ought to transit the planet’s central meridian round 10:37 p.m. EDT. Features on Jupiter stay nearer to the central meridian than the limb for 50 minutes earlier than and after they transit.


■ Once the Moon is nicely up within the east tonight, look left of it by about a fist and a half for the little Pleiades cluster. Can you pick this sparkle-patch by the moonlight? Binoculars make it simple.

Look a little greater than a fist under the Pleiades for orange Aldebaran on the rise.


■ The waning gibbous Moon shines within the east after darkish this night. You may have binoculars to select the Pleiades few levels to its left or higher left, as proven under. Much simpler is shiny Capella many instances farther left of the Moon.

As night time advances, Aldebaran comes up under or decrease left of the Moon. And by midnight, Orion is clearing the japanese horizon far under all of them.


■ Tonight the waning Moon shines close to Aldebaran, as proven under.

In October each year, the Moon commits its passage by Taurus when it is waning gibbous.

■ This is the time of year when the Big Dipper lies down horizontal low within the north-northwest after darkish. How low? The farther south you’re, the decrease. Seen from 40° north (New York, Denver, Madrid) even its backside stars twinkle practically ten levels excessive. But at Miami (26° N) your complete Dipper skims alongside out of sight slightly below the northern horizon.


This Week’s Planet Roundup

Mercury is heading towards its greatest morning apparition of the year. By about Monday October 18th, search for it low above the east horizon about 50 minutes earlier than dawn. On that morning it is nonetheless solely magnitude +0.7, so it’s your decision binoculars.

But it brightens and will get a little larger day-after-day. Just 4 days later, on Friday morning the twenty second, Mercury is greater than twice as shiny at magnitude –0.2. Next week it’s going to practically double in brightness once more.

Don’t confuse Mercury with Arcturus, which is above the east-northeast horizon (relying in your latitude) off to Mercury’s left.

Mars stays out of sight behind the glare of the Sun.

Venus, good at magnitude –4.4, shines in southwest throughout twilight, crossing from Scorpius into the toes of Ophiuchus. It units about a half hour after twilight’s finish.

On Saturday the sixteenth Venus is passing 1.4° north (higher proper) of Antares, which is way fainter, orange, and twinkling. Every night thereafter, Antares falls away farther to Venus’s decrease proper. By the twenty second they’re a good 6° aside.

Jupiter and Saturn proceed to shine within the south throughout night, 15° aside on reverse sides of Capricornus. Jupiter is the eye-grabber at magnitude –2.6. Saturn, to its proper or decrease proper, is a twentieth as shiny at magazine +0.6.

In twilight they shine equally excessive. As the night progresses watch them tilt as they transfer to the appropriate, with Saturn turning into the decrease one. Saturn units round midnight or 1 a.m. daylight-saving time, adopted by Jupiter about an hour later.

After darkish look 23° (two fists at arm’s size) decrease left of Jupiter for 1st-magnitude Fomalhaut, as proven at the highest of this web page.

Here’s a beginner’s telescopic guide to Jupiter.

Jupiter on October sixth, imaged by S&T‘s Sean Walker with a 12-inch reflector in New Hampshire. North is up. “We were treated to some excellent seeing conditions.” he writes. “I spent hours shooting and observing the planet, watching the GRS transit, as well as the dark barges in the NEB, and the series of white ovals south of the SEB. It was a magical night of observing — I was seeing the first diffraction ring around Io and Europa; don’t think I can ever recall seeing that before. Wish I could have shared it with others.”

Uranus (magnitude 5.7, in southern Aries) climbs excessive within the east by 10 p.m.

Neptune (magnitude 7.8, at the Aquarius-Pisces border) is already nicely up within the within the southeast at twilight’s finish.

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 on longitude (primarily Moon positions) are for North America.

Eastern Daylight Time, EDT, is Universal Time minus 4 hours. Universal Time is also called UT, UTC, GMT, or Z time. To change into extra professional about time methods than 99% of the folks you may ever meet, see our compact article Time and the Amateur Astronomer.

Want to change 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 out of doors nature passion. For an easy-to-use constellation information masking 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 commonplace is the Pocket Sky Atlas (in both the (*23*)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 arduous 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; practically thrice as many. The subsequent up, as soon as 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 to learn How to Use a Star Chart with a Telescope.

You’ll additionally need a good deep-sky guidebook, equivalent to the large Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope substitute charts? Not for learners, I do not assume, and never on mounts and tripods which might be 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 together with your
earbuds in place, take heed to Kelly Beatty’s month-to-month
podcast tour of the heavens above. It’s free.

            — Carl Sagan, 1996

“Facts are stubborn things.”
            — John Adams, 1770

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