The Ghost of Summer Suns. Halloween is near, and this means that Arcturus, the star sparkling low in the west-northwest in twilight, has become "the Ghost of Summer Suns." For several days centered on October 25th every year, Arcturus occupies a special place above your local landscape. It closely marks the spot where the Sun stood at the same time, by the clock, during hot June and July — in broad daylight, of course!

So at Halloween season every year, you can see Arcturus as the chilly ghost of the departed summer Sun.


■ Full Moon (exact at 4:24 p.m. EDT). The Moon rises at sunset. As twilight deepens and the Moon climbs higher, Jupiter shines just 3° or so below or lower left of it (for North America). Jupiter is currently 1,500 times farther away than the Moon and it's 40 times larger in diameter!

Watch them appear to draw closer together through the evening. Jupiter will pass 2° below the brilliant Moon in the early morning hours.

It's no surprise that they appear in the same spot of the sky. Both are very close to the opposition point, the point on the sky opposite from the Sun as seen from Earth's point of view.

Moon with Jupiter, evenings of October 27, 28, 29, 2023
The full Moon and full Jupiter shine together as they climb in evening twilight.

■ A very slight partial lunar eclipse occurs while the full Moon is visible from Europe, Africa, and Asia. The partial eclipse will be deepest at 20:14 Universal Time October 28, when just 13% of the Moon's diameter will be shaded in the umbra of Earth's shadow. The entire partial eclipse runs from 19:34 to 20:54 UT. Slight penumbral shading will be visible on the Moon's celestial southeast to south side for roughly 45 minutes before and after partial eclipse.

The Moon and Jupiter together in the west in early dawn, Oct. 29, 2023
In early dawn less than 12 hours later, the Moon and Jupiter have swung all the way over to shine in the west-northwest.

You may be up and around by then. Because we're still on daylight-saving time (until November 5th), this week the Sun rises its latest of the year by the clock (for those of us at mid-northern latitudes).


■ Around the time when twilight fades out, zero-magnitude Capella has risen exactly as high in the northeast as zero-magnitude Vega has sunk in the west-northwest.

■ Algol in Perseus should be at its minimum brightness late tonight, magnitude 3.4 instead of its usual 2.1, for about two hours centered on 1:23 a.m. Eastern Daylight Time, 10:23 p.m. Pacific. Algol takes several additional hours to fade and to rebrighten.


The Summer Triangle Effect. Here it is nearly the end of October, but Deneb still shines near the zenith as the stars come out. And brighter Vega is still not far from the zenith, toward the west. The third star of the "Summer" Triangle, Altair, remains very high in the southwest. They seem to have been there for a couple months! Why have they stalled out?

What you're seeing is the result of sunset and darkness arriving earlier and earlier during autumn. Which means if you go out and starwatch soon after dark, you're looking earlier and earlier by the clock. This counteracts the seasonal westward turning of the constellations.

Of course the "Summer Triangle effect" applies to the entire celestial sphere, not just the Summer Triangle. But the apparent stalling of that bright landmark inspired Sky & Telescope to give the effect that name many years ago, and it stuck.

Of course, as always in celestial mechanics, a deficit somewhere gets made up elsewhere. The opposite effect makes the seasonal advance of the constellations seem to speed up in early spring. The spring-sky landmarks of Virgo and Corvus seem to dash away westward from week to week almost before you know it, due to darkness falling later and later. Let's call this the "Corvus effect."


■ The waning Halloween Moon, three days past full, rises in the northeast soon after dark. Watch for it to come up lower right of Capella, and a similar distance lower left of the Pleiades (for North America).

About four fists to the Moon's upper right shines Jupiter, the brightest point in the evening sky. Jupiter this year is in Aries. Look for the Ram's two brightest stars, Hamal and Sheratan, above Jupiter by about one fist. They're lined up nearly horizontally, about two fingers at arm's length apart. They're magnitudes 2.0 and 2.6. Hamal, the brighter one, is on the left.

And can you see fainter Mesarthim, magnitude 3.8, just a bit lower right of Sheratan?


NEW: The naked-eye star Kappa Geminorum, magnitude 3.6, will be briefly occulted late tonight by a tiny asteroid (magnitude 19!) for one second or less, writes David Dunham of the International Occultation Timing Association. The occultation should occur along a path running from New Mexico through northern Virginia from 6:38 to 6:40 November 2 UT. The star will be low in the east, especially for the western states. The occultation may be partial or annular! That could be a first for recorded asteroid occultations. Kappa Gem is a G III yellow giant with a disk estimated to be 2.8 milliarcseconds wide. The asteroid, only a couple miles across, should be about 2.7 milliarcseconds wide. (Kappa Gem has an 8th-magnitude companion star 7 arcseconds away; don't be confused by it.)

Global map of the occultation path, with times. Zoom in on this map for new precise path-edge predictions, updated Oct. 29, plotted on Google Earth. More info. If you can get yourself positioned on the path, writes Dunham, your chances of catching the event are good. Time-stamped video recordings are sought, to deduce the asteroid's size and shape and to refine its orbit. "If you are mobile," writes Dunham, "send me a message to [email protected] so I can suggest a line for you to aim for," to create well-spaced picket fence coverage of the asteroid's silhouette.

■ Vega is the brightest star high in the west after dark. To its right or lower right by 14° (nearly a fist and a half) look for Eltanin, the nose of Draco the Dragon. The rest of Draco's fainter, lozenge-shaped head is a little farther behind. Draco always eyes Vega as they wheel around the sky.

The main stars of Vega's own constellation, Lyra — also pretty faint — extend from Vega 7° to the side opposite the head of Draco.

Farther on in that same direction, you'll see that Lyra's length points to Altair. This line is the bottom segment of the Summer Triangle.

■ Algol in Perseus should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for about two hours centered on 10:12 p.m. Eastern Daylight Time, 7:23 p.m. Pacific. Algol takes several additional hours to fade and to rebrighten.


■ The waning gibbous Moon rises around 9 or 10 p.m. Once it's well up, you'll see it forming a nice, not quite equilateral triangle with Castor and Pollux to its left and lower left. The triangle shrinks as the night advances and the Moon creeps toward Pollux. By dawn on the 3rd, the triangle is as shown below.

Moon passing Castor and Pollux at dawn, Nov 2-4, 2023
The Moon crossing Gemini in the southwest in early dawn. Yes, you can get yourself out of bed that early; we're still not quite on standard time yet, so the Sun rises its very latest.


■ Spot bright Altair high in the southwest soon after dark. Brighter Vega is far to its right.

Two distinctive little constellations lurk above Altair: Delphinus the Dolphin, hardly more than a fist at arm's length to its upper left, and smaller, fainter Sagitta the Arrow, slightly less far to Altair's upper right. Is your sky too bright for them? Use binoculars!


■ Last-quarter Moon tonight (exactly so at 4:37 a.m. Sunday morning EDT). The half-lit Moon rises around 11 or midnight, in Cancer. Watch for it to come up over the horizon about two fists at arm's length below or lower left of Castor and Pollux.

■ Algol shines at minimum light for a couple hours centered on 7:01 p.m. EDT.

■ Daylight-saving time ends at 2 a.m. tonight for most of North America. Clocks fall back an hour.


■ After dark this week, Capella shines in the northeast. The Pleiades are up in the east-northeast three fists to Capella's right. As evening grows later, you'll find orange Aldebaran climbing below the Pleiades. Then by about 10 p.m. (depending on your location), Orion clears the eastern horizon below Aldebaran.

This Week's Planet Roundup

Mercury is hidden in the glare of the Sun.

Venus, brilliant at magnitude –4.4 under the hind feet of Leo, shines high in the east before and during dawn. It rises nearly 2½ hours before dawn's first light a weird late-night apparition coming up over the eastern horizon.

Mars is out of sight behind the glare of the Sun. It will remain so into early winter.

Jupiter (magnitude –2.9, in Aries) is at opposition November 2nd. It rises around sunset, dominates the east during evening, stands highest in the south around 1 a.m. daylight-saving time, and sets around sunrise. In a telescope Jupiter now appears as big as it gets: 49 or 50 arcseconds wide all week. Don't miss this chance!

Jupiter's non-Red-Spot side on Oct. 28, 2023
Jupiter's non-Red-Spot side imaged by Christopher Go on October 28th. South is up. The South and North Equatorial Belts are almost equally prominent, and that's all a 2.4- to 4-inch telescope may show. A 6-inch in fine seeing might begin to show that the NEB has much more turbulent borders, and that bluish festoons of cloudless air extend from its south edge into the bright Equatorial Zone.

This stacked-video image, taken with a 14-inch scope and somewhat contrast-boosted, also captures at least 10 tiny white outbreaks of upwelling clouds along the turbulent NEB/EZ interface.

Saturn (magnitude +0.7, in dim Aquarius) glows steady yellowish in the south these evenings. Fomalhaut twinkles nearly two fists at arm's length to its lower left.

Saturn (and Dione) Aug 30, 2023
Saturn on August 30th, imaged by Christopher Go. South is up. Saturn was barely past opposition then, so the globe's shadow on the rings behind it was barely becoming visible on the east side (at the right here). The shadow on the rings now is wide and prominent.

Uranus, magnitude 5.6 in Aries, resides 10° east of Jupiter. It comes to opposition November 13th. In a telescope at high power Uranus is a tiny but distinctly nonstellar ball, 3.8 arcseconds in diameter. See the finder charts for it in the November Sky & Telescope, pages 48-49.

Neptune, magnitude 7.8 at the Aquarius-Pisces border, is high in early evening 25° east of Saturn. Neptune is only 2.3 arcseconds wide: harder to resolve as a ball than Uranus is, but definitely nonstellar at high power.

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 and graphics that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time minus 4 hours. Eastern Standard Time (EST ) is UT minus 5 hours. UT is also known as UTC, GMT, or Z time.

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 a more detailed 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 much more 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 all 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 mag 9.75). And be sure to read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning the sky. 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."

But finding a faint telescopic object the old-fashioned way with charts isn't simple either. Learn the tricks at How to Use a Star Chart with a Telescope

Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye 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


You must be logged in to post a comment.