This Week's Sky at a Glance, October 3 – 12

FRIDAY, OCTOBER 3

■ In tonight's sky Vega is the brightest star very high toward the west. It's still almost overhead at nightfall; it descends as the hours pass.

When you look at Vega while facing west, to its right by 14° (a little more than a fist at arm's length) you'll find 2nd-magnitude Eltanin, the nose of Draco the Dragon. The rest of Draco's fainter, lozenge-shaped head is a little farther right. Draco always eyes Vega as they wheel around the sky.

Farther on, behind Draco's head, his long, arched back and tail loop around the Little Dipper in the north.

The main stars of Vega's own constellation, Lyra — faint by comparison — extend from Vega in the direction opposite from Eltanin.

■ For telescope users, two of Jupiter's satellites, Io and Europa, are both casting their shadows onto the planet's cloudtops from 2:49 to 4:17 a.m. EDT tonight (11:49 p.m. to 1:17 a.m. PDT).

SATURDAY, OCTOBER 4

■ Find Saturn glowing steadily about a fist to the Moon's left or lower left, and Fomalhaut twinkling nearly twice as far to the Moon's lower right, as shown for October 4 below.

SUNDAY, OCTOBER 5

■ The Moon, just a day from full, shines low in the southeast at nightfall with Saturn a couple degrees below or lower right of it, as shown above. As the night proceeds into the early morning hours, watch them draw farther apart while Saturn appears to swing straight down underneath the Moon.

■ Saturn's moon Titan just barely casts its shadow onto Saturn tonight. This is the final trace of the 2025 series of these events. Titan's tiny shadow will just skim Saturn's north pole around 5:32 October 6th UT, which is 1:52 a.m. October 6th Eastern Daylight Time; 10:53 p.m. October 5th PDT. The shadow will be just a tiny notch in Saturn's north limb. Can you watch it come and go? See Bob King's Titan Shadow Transit Season Underway.

MONDAY, OCTOBER 6

■ Full Moon (exactly full at 11:48 p.m. EDT). In fact it's a supermoon: near perigee, appearing 4% larger and 13% brighter than an average full Moon. This is the first and smallest of a series of three full supermoons.

Above the Moon after dark, look for the Great Square of Pegasus. To the right of the Moon shines Saturn, and farther left of the Moon is the compact asterism of the two or three brightest stars of Aries.

TUESDAY, OCTOBER 7

■ Vega is the brightest star high in the west these evenings. Less high in the southwest is Altair, not quite as bright. Just upper right of Altair, by a finger-width at arm's length, is little orange Tarazed. Down from Tarazed runs the dimmer stick-figure backbone of the constellation Aquila, the Eagle, alongside the spine of the Milky Way.

WEDNESDAY, OCTOBER 8

■ Ceres, the largest asteroid and the first discovered, remains in binocular range at magnitude 7.6 a few degrees west of Eta Ceti. Use the finder chart in the October Sky & Telescope, page 50. The tick marks on its path there are for 0:00 UT on the dates indicated, which falls on the evening of the previous date for the Americas.

THURSDAY, OCTOBER 9

■ The waning gibbous Moon rises close to the Pleiades around the end of twilight. The Moon draws nearer to them as the night proceeds. To help see them through the Moon's glare, cover the Moon with your fingertip. Or better, two fingertips, one for each eye. Close one eye and position a fingertip onto the Moon, then do the same for the other eye with another fingertip. Then without moving, open both eyes.

Late tonight the Moon's bright limb will occult four of the Pleiades, ranging from magnitude 2.9 to 3.9, for parts of the U.S. and Canada. For maps and timetables go to the IOTA bright-star occultation predictions page and scroll down to the four events for Oct. 10; that's the UT date.

FRIDAY, OCTOBER 10

■ This is the time of year when, in early evening, W-shaped Cassiopeia stands on end halfway up the northeastern sky — and when, off to its left in the north, the dim Little Dipper extends leftward from Polaris.

SATURDAY, OCTOBER 11

■ As October proceeds, Deneb replaces Vega as the zenith star of early evening (for skywatchers at mid-northern latitudes). Accordingly, Capricornus has replaced Sagittarius as the zodiacal constellation posing low in the south.

■ In early dawn tomorrow the 12th, the almost-last-quarter Moon is on its way heading toward Jupiter, Pollux, and Castor, as shown below.

SUNDAY, OCTOBER 12

■ Last-Quarter Moon tonight (exact at 2:13 p.m. Monday the 13th). In early dawn Monday morning the Moon stands between the stick figures of the Gemini twins (for the longitudes of the Americas), with Jupiter just below them.

■ Algol should be at its minimum brightness tonight, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 12:42 a.m. EDT; 9:42 p.m. PDT. Algol takes several hours before and after to fade and to rebrighten. Comparison-star chart giving magnitudes, with north up.

This Week's Planet Roundup

Mercury remains hidden low in the afterglow of sunset.

Venus rises shortly before the beginning of dawn. Watch for it to come up a little left of due east.

Venus shines at the Leo-Virgo border. After it's up but before the sky gets too bright, look for Regulus, much fainter, increasingly far above it and a bit to the right. Regulus is 18° above Venus on Saturday morning October 4th, and 27° above it a week later on the 11th.

Mars is out of sight deep in the glow of sunset, as it will be for the rest of the year.

Jupiter, magnitude –2.1 in Gemini, rises around midnight daylight-saving time and dominates the east as the morning hours advance. Castor and Pollux shine above it. By the beginning of dawn the three stand very high in the east — with Procyon below them, Orion off to Procyon's right, and Venus coming into view low down in the east.

Saturn is up in the east-southeast as night falls. Every evening it's a little higher as the stars come out. Spot it lower right of the Great Square of Pegasus, which is standing on one corner. At magnitude +0.7 Saturn outshines the stars of the Great Square, which are about 1½ or 2 magnitudes fainter.

Saturn transits the meridian (due south) around 11 or midnight. In a telescope its rings remain nearly edge-on.

Uranus (magnitude 5.6, in Taurus near the Pleiades) rises shortly before dusk and is high by 10 p.m. At high power in a telescope it's a tiny but definitely non-stellar dot, 3.6 arcseconds wide.

Neptune is a telescopic "star" of magnitude 7.8, a dim pinhead just 2.4 arcseconds wide. Use the finder chart for Neptune with respect to Saturn in the September Sky & Telescope, page 49. With a pencil, put a dot on the path of each of the two planets for your date.

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. 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.

For the attitude every amateur astronomer needs, read Jennifer Willis's Modest Expectations Give Rise to Delight.

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. Both show all 30,000 stars to magnitude 7.6, and 1,500 deep-sky targets — star clusters, nebulae, and galaxies — to search out among them.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many, as well as many more deep-sky objects. It's currently out of print, but maybe you can find one used.

The next up, once you know your way around well, are the even larger Interstellarum atlas (with 201,000+ stars to magnitude 9.5 and 14,000 deep-sky objects selected to be detectable by eye in large amateur telescopes), and Uranometria 2000.0 (332,000 stars to mag 9.75, and 10,300 deep-sky objects). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet (which many observers find more versatile) 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. The pinnacle for total astro-geeks is the new Annals of the Deep Sky series, currently at 11 volumes as it works its way forward through the constellations alphabetically. So far it's up to H.

Can computerized telescopes replace charts? Not for beginners I don't think, and not for scopes 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 how to explore the sky. 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 and a curious mind." Without these, "the sky never becomes a friendly place."

If you do get a computerized scope, make sure that its drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

However, finding faint telescopic objects the old-fashioned way with charts isn't simple either. Do learn the essential 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; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence."
            — John Adams, 1770