The Planets


1934 Map of Mercury
Astronomers used Eugène Antoniadi’s Mercury maps for decades, until new developments in telescopes brought the planet into sharper focus. On this 1934 map south is at the top, as seen through an inverting telescope.

Mercury is deep in the pre-dawn solar glare at the beginning of October, just having come to inferior conjunction on September 30. It may first be visible on October 11 a mere half an hour before sunrise, about 1° from the waning crescent Moon. The innermost planet is 20° below Jupiter at this time, but the gap between the two grows as the month progresses.

Mercury reaches greatest western elongation the night of October 15 – 16, when it stands 18° from the Sun and rises at the very start of astronomical twilight. By the final week of the month, the sun-scorched world brightens to magnitude -1 but descends quite low into the sunrise.

A backyard telescope will reveal Mercury’s changing form. On the 11th, the planet’s disk spans 8” and appears 31-percent illuminated. Five days later, at greatest elongation, its diameter has shrunk to 7” and its phase has waxed to exactly half-lit.

Seeing surface markings on Mercury with a small telescope, or with almost any telescope on Earth, is extremely difficult. Some experienced amateur observers report seeing dusky markings, but no useful information has ever come from such sightings. These observations do not appear to correspond to real features as shown in spacecraft images.

Finder map (early October) – 30 minutes before sunrise, looking east.
Finder map (mid-October) – 30 minutes before sunrise, looking east.
Finder map (late October) – 30 minutes before sunrise, looking east.


Conjunction Over Chile
In the night sky over ESO’s Very Large Telescope (VLT) observatory in Chile, the Moon shines along with two bright companions: Venus and Jupiter. Such close groupings of celestial bodies are called conjunctions. ESO / Y. Beletsky

The stage is set for the finest planetary conjunction of the year. Venus, Mars and Jupiter – in that order from top to bottom – start the month almost evenly spaced and separated by only 17° in the predawn darkness. The spectacular gathering only gets better with the arrival of each new morning.

A waning crescent Moon joins the trio on October 8, just 4° to the upper right of Venus, with Mars and Jupiter 9° and 13° farther lower left, respectively. The following morning, the Moon forms a compact triangle with Mars and Jupiter, 10° below Venus and Leo’s brightest star, 1st-magnitude Regulus.

On October 17 and 18, Mars shines less than 0.5° from Jupiter, with magnitude -4.4 Venus about 7° to the upper right. The 23rd finds Mars and Venus 4.5° apart with Jupiter midway between.

Three mornings later, on October 26, Venus blazes just 1° south of Jupiter (the circle containing Venus, Jupiter and Mars is now only 3.5° in diameter). October 26 is also the day Venus reaches greatest elongation, 46° west of the Sun and more than 25° high above the eastern horizon as twilight begins.

By October’s final morning, Mars moves away from Jupiter, while Venus has closed to within 1.4° of Mars. The latter two will experience a close conjunction of their own, less than 1° apart from November 2nd through 4th.

Venus’ telescopic appearance changes dramatically during the month. On October 1, the planet’s disk spans 33” and appears 35-percent lit; by the 31st, the disk measures 23” across while the phase thickens to 53-percent sunlit.

Finder map (early October) – 30 minutes before sunrise, looking east.
Finder map (mid-October) – 30 minutes before sunrise, looking east.
Finder map (late October) – 30 minutes before sunrise, looking southeast.


Syrtis Major
This image of Mars taken by the Viking orbiter in 1980 shows the large, dark expanse of the extinct shield volcano Syrtis Major. USGS Astrogeology Science Center

Mars continues to flee ahead of Earth in orbit around the Sun. Nevertheless, our world is slowly gaining on the Red Planet, and, as we do so, Mars climbs higher each day into the eastern sky before dawn. On the mornings of October 17 and 18, Mars is within 0.5° of Jupiter. By the 31st, it is 1.4° to Venus’ lower left.

The orange-gold world lies about 215 million miles (346 million kilometers) from Earth around mid-month. Coupled with the planet’s small physical size, this large distance renders Mars tiny in the eyepiece, just 4” across. Only the largest backyard telescopes will show surface features with any clarity.

Under good conditions, an amateur telescope will show Mars’ polar ice caps and the main dark areas. These were once thought to be seas but now are known to be regions where winds in the tenuous atmosphere have blown away the red, dusty material that covers most of the planet, exposing the darker layers below.

The two most prominent dark surface markings are the Syrtis Major in the equatorial region of the planet and Acidalia Planitia in the north; the Syrtis Major is V-shaped, and much the easiest to see. Do not expect to be able to make out a lot on Mars the first time you look through your telescope. Observing takes lots of practice, and you will find that many hours of experience will make an enormous difference to what you can make out.

Finder map (early October) – 30 minutes before sunrise, looking east.
Finder map (mid-October) – 30 minutes before sunrise, looking east.
Finder map (late October) – 30 minutes before sunrise, looking southeast.


Jupiter Imaged by Hubble
Gas giant Jupiter is the solar system’s largest world, with about 320 times the mass of planet Earth. This sharp Hubble image was taken on April 21, 2014. NASA / ESA / Amy Simon

Jupiter rises in the east two hours before sunup and is still east of the meridian at dawn. The gas giant starts October well below Venus and Mars, but during the next two weeks, the gap between the three worlds slowly diminishes. What follows is arguably the finest tight trio of bright planets we will see for many years.

On October 17 and 18, Jupiter brushes less than 0.5° from Mars. Then, for the final event in an epic series of close conjunctions, Venus comes to within 1° of Jupiter on the 26th.

That morning, Jupiter lies 561 million miles (903 million kilometers) away, or more than 8.5 times farther than Venus. Even so, a telescope will show Jupiter’s 33” width is 1.35 times the size of Venus’ disk. The reason, of course, is that Jupiter, the solar system’s largest planet, is 12 times Venus’ size.

Jupiter will continue to rise earlier as Earth’s motion around the Sun carries us toward opposition with the planet in early March 2016. At that point, we will fly between Jupiter and the Sun, and they will be on opposite sides of our sky. Until then Jupiter will brighten further, because the distance between us is steadily decreasing.

Jupiter is currently magnitude -1.8, but at opposition, it will blaze at magnitude -2.5. On January 8, 2016, the planet prepares for that climax by starting its retrograde (westward) motion against the stars.

Finder map (early October) – 30 minutes before sunrise, looking east.
Finder map (mid-October) – 30 minutes before sunrise, looking east.
Finder map (late October) – 30 minutes before sunrise, looking southeast.


About 45 minutes after sunset this month, Saturn rides above the deepening orange twilight in the southwest. It forms a nice pair with 1st-magnitude Antares, located 10° southeast (lower left).

As the ringed planet moves eastward relative to the background stars, it passes 0.7° due north of Graffias (Beta Scorpii) on October 24. At magnitude +0.6, Saturn’s yellowish globe shines four times brighter than Beta Scorpii, the head of the celestial Scorpion.

Saturn is little more than 10° high in early October, as seen from around latitude 40° north. By month’s end, the planet has dropped to 5° altitude at the equivalent time and may be hidden by trees or buildings. If you want to catch a view of Saturn through a telescope, do so early in the month!

Even when it hangs low, observing Saturn is nothing short of stunning. You will see the planet’s 16”-diameter disk wrapped by a spectacular ring system that spans 36”. The rings tilt 25° to our line of sight this month, heading for a maximum approaching 27° in 2017. Saturn’s rings appeared edge on in 2009 and will do so again in 2025.

Any scope will also show Saturn’s biggest and brightest moon, 8th-magnitude Titan. It orbits the planet once every 16 days. You can find this satellite south of Saturn October 2 and 18, and north of the ringed world October 10 and 26.

Finder map (early October) – one hour after sunset, looking southwest.
Finder map (mid-October) – one hour after sunset, looking southwest.
Finder map (late October) – 30 minutes after sunset, looking southwest.


Uranus from Voyager
Above is Voyager’s highest resolution picture of Titania, Uranus’ largest moon. The picture is a composite of two images recorded from a distance of 229,000 miles (369,000 kilometers). NASA / The Voyager Project

Uranus rises about two hours after Neptune and stands 10° above the eastern horizon shortly after evening twilight fades. It appears against the background of Pisces the Fish, between 2° and 3° southeast of 4th-magnitude Epsilon Piscium.

You will have an easier time viewing Uranus if you wait until midevening when it climbs reasonably high in the east-southeast. Use the Great Square of Pegasus as a guide. Start by drawing an imaginary line from Beta to Gamma Pegasi, the top and bottom of the asterism, respectively, on October evenings. Then continue the line and head slightly left to pick up Epsilon Piscium.

Uranus is not one of the five classic naked-eye planets, but observers under dark skies should still be able to glimpse the first “discovered” planet without optical aid. It remains at magnitude +5.7 or brighter all year; around opposition October 12 it will be magnitude +5.6.

If you use a telescope at high magnification, on a night with good seeing conditions, Uranus appears as a tiny featureless disk with a pale greenish hue. The planet’s 27 known natural satellites are beyond easy reach of most amateur telescopes, for visual observations.

However, if you are equipped with one of the very large-aperture telescopes that have become common nowadays you will find it possible to glimpse the largest and brightest of the moons. Titania (magnitude +13.9) and Oberon (magnitude +14.1) will be the easiest because they attain the greatest separation from the glare of the planet.

Finder map – field width 15°, stars to magnitude +8.


Neptune Composite Scene
Based on the images recorded by Voyager 2 during its close encounter, this composite scene covers Neptune, largest moon Triton, and the faint system of rings. Rolf Olsen / NASA / The Voyager Project

Neptune reached opposition and peak visibility on the American evening of August 31. During October, it remains visible almost all night, reaching its highest point around 10 P.M. local daylight time.

You can find Neptune with binoculars or a telescope in Aquarius the Water-Bearer, roughly one-third of the way from 5th-magnitude Sigma Aquarii to 4th-magnitude Lambda. The planet glows at magnitude +7.8 and its blue-gray disk appears 2.5” across, just big enough to be resolved under good conditions.

Denser than the other gas giants, Neptune probably has ice and molten rock in its interior, although rotational data imply that these heavy materials are spread out rather than concentrated in a small core. The atmosphere is swept by winds moving at up to 2,300 feet (700 meters) per second, the fastest found on any planet. At the equator, the winds blow westwards (retrograde) and beyond latitude 50° they become eastwards. Temperature measurements show that there are cold mid-latitude regions with a warmer equator and pole.

Neptune’s 14 known moons include Nereid, with the most eccentric orbit of any planetary satellite, seven times as distant from the planet at its farthest compared with its closest approach; and Triton, the only large moon in the solar system with a retrograde orbit, which is an orbit in the opposite direction to that of Neptune’s.

Finder map – field width 15°, stars to magnitude +8.5.


Pluto’s Tartarus Dorsa Region
A high-resolution, enhanced-color image of Pluto’s Tartarus Dorsa mountainous region. Shadows near the terminator, the line between Pluto’s dim day and night, emphasize a rough, scaly texture. NASA / JHUAPL / SWRI

Pluto wanders far from the ecliptic, where the major planets reside. It lies north of the Teapot asterism in Sagittarius, following a number of years in Ophiuchus and Serpens. Look for it as soon as full darkness falls, due west of magnitude +3.5 Xi2 Sagittarii at the following distances: 42’ (October 1); 35’ (October 15); and 21’ (October 31).

At magnitude +14.2, Pluto is hard to spot visually even under the best conditions. You will likely need at least a 10-inch scope, although a smaller telescope with a CCD camera attached will also work. Take images a few nights apart, and Pluto’s motion relative to the background stars will betray its location.

On July 14 this year, NASA’s New Horizons spacecraft has reached its closest point to Pluto, about 7,750 miles (12,472 kilometers) above the surface. The probe sent back breathtaking photographs of Pluto in high resolutions, which reveal a varied surface with frozen plains and ice mountains. Rising to an estimated 11,000 feet (3,500 meters) the mountains are likely composed of water ice. They are also likely young, with an estimated age of 100 million years or so.

After passing by Pluto, New Horizons now continues further into the Kuiper Belt. Its target is 2014 MU69, an icy object situated 43.3 astronomical units from the Sun.

Astronomers know little about 2014 MU69, other than it is an incredibly dim +25.6-magnitude blip that takes about 293 years to orbit once around Sol. Its diameter is estimated to be about 30 miles (45 kilometers) across, roughly ten times the size of a typical comet.

Coarse finder map – field width 10°, stars to magnitude +8.5.
Fine finder map – field width 1°, stars to magnitude +14.5.

The Deep Sky

NGC 7331
About 40 million light-years distant in the constellation Pegasus, NGC 7331 is often touted as an analog to our own Milky Way Galaxy. Adam Block / Mount Lemmon SkyCenter / University of Arizona

Among the stars of Pegasus, the Winged Horse, are some of the fall sky’s best galaxy groups for backyard observers. Stephan’s Quintet is probably the best-known example of such a compact gathering, comprised of four gravitationally interacting galaxies and a prominent foreground galaxy, projected onto the more distant group by chance. But have you ever heard of the “Deer Lick Group”? No? Well, read on.

A trail blaze on the path to Stephan’s Quintet, NGC 7331 also anchors its own galaxy grouping. It is accompanied by several faint companions, including the smaller spiral galaxies NGC 7335 and NGC 7337, which are probably ten times farther away than NGC 7331. In the 1980s, author Tom Lorenzin bestowed the common name on this galaxy group to honor the Deer Lick Gap, which lies in the mountains of North Carolina. Apparently, Tom had a memorable view of these galaxies from there.

NGC 7335 and NGC 7337 are often erroneously referred to as satellites, but they are not associated with NGC 7331. The two companions glow at around magnitude +14, way too faint for most amateur scopes. NGC 7331, however, can even be spotted with larger binoculars.

Located about 4.5° northwest of Eta Pegasi, near the border of Lacerta, NGC 7331 was discovered in 1784 by William Herschel, and was one of the brightest galaxies overlooked by Messier in his catalog. It appears nearly edge on, tilted at an inclination of 77°. Its structure is remarkably similar to our own Milky Way Galaxy, with a comparable overall mass, spiral structure, distribution of stars, and central supermassive black hole.

Shining with the combined light of a 9th-magnitude star, NGC 7331 appears as a small fuzzy patch when viewed through binoculars. With an 8-inch telescope, a bright core appears and the beginnings of wispy arms. At 12-inches in aperture, spiral patterns emerge, and with good seeing conditions you will observe “patchiness” in the structure. Nebulous areas are revealed and the western half of the galaxy is deeply outlined with a dark dust lane.

Finder map – field width 15°, stars to magnitude +8.5.


Vesta’s South Pole
Vesta shows light and dark features, hills, craters and cliffs, much like our Moon. The Dawn spacecraft took this image of the asteroid’s south pole from a distance of about 1,700 miles (2,700 kilometers). NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / The Dawn Project Team

For years, astronomers had little interest in asteroids – in fact, they considered them a nuisance. Those of them trying to count stars found that asteroids made their work harder, and those trying to photograph stars found their plates filled with irritating little streaks. It was not until fairly recently that astronomers decided that asteroids are in fact very interesting indeed.

To date, 12 main-belt asteroids have been photographed close up (from largest to smallest): 1 Ceres, 4 Vesta, 21 Lutetia, 253 Mathilde, 243 Ida, 433 Eros, 951 Gaspra, 2867 Steins, 5535 Annefrank, 4179 Toutatis, 9969 Braille and 25143 Itokawa.

The Dawn spacecraft imaged Vesta and Ceres, and the Rosetta probe passed within 1,965 miles (3,162 kilometers) of Lutetia in July 2010. The Galileo spacecraft studied Ida and Gaspra on its way to Jupiter, while the NEAR Shoemaker spacecraft visited Mathilde and Eros.

All these robotic space missions showed that asteroids have a wide range of shapes mimicked well by potatoes. Some are binaries or contact doubles, but the bigger ones like 4 Vesta are nearly round. As these huge boulders rotate, their brightnesses change and enable astronomers to figure out how long it takes them to turn. In Vesta’s case, the day passes quickly, in just 5.34 hours.

For a couple of days around its September 29 opposition, Vesta is easy to spot in binoculars at magnitude +6.2. It is still as bright as +6.8 on October 31, +7.5 on November 30, and +8 at the end of the year. Throughout this month, the asteroid remains visible nearly all night, climbing highest in the south around midnight local daylight time.

To find Vesta, first locate the 2nd-magnitude star Beta Ceti. Then point your binoculars 10° to the north-northwest at magnitude +3.5 Iota Ceti. During the second half of October, Vesta will be the brightest point of light south of Iota.

Finder map – field width 15°, stars to magnitude +8.5.


The PanSTARRS Facility
The PanSTARRS PS1 and PS2 telescopes, located at the summit of Maui’s Haleakala volcano. Comet C/2014 S2 was discovered from this facility on September 22, 2014. PS1 Science Consortium / University of Hawaii Institute for Astronomy

Comet PanSTARRS (C/2014 S2) should show up nicely through a 4-inch telescope under a country sky. Glowing around 10th magnitude and with a predicted diameter of three arcminutes, this visitor from the solar system’s icy depths likely will appear similar in brightness and size to some of the fainter elliptical galaxies in the Messier catalog.

The comet belongs to both the evening and morning skies this month because it passes close to Polaris. Because the North Star never sets for observers north of the equator, C/2014 S2 remains visible all night. To see it best, try to sidestep moonlight. In early October, dark skies come in early to mid-evening before the Moon rises. During the month’s second half, the waxing Moon demands a switch to predawn hours.

As October begins, PanSTARRS appears 2.5° south of Polaris. The gap closes to only 0.5° a few days later, on October 5. Under a rural sky, a rich-field telescope will show the 8th-magnitude open star cluster NGC 188 just southwest of Polaris, in the same low-power field.

By month’s end, the comet skims past Zeta Ursae Minoris, the star at the end of the Little Dipper’s handle. It will continue to move south from that point, getting slightly brighter as it heads toward its mid-December perihelion.

Finder map – field width 30°, stars to magnitude +7.5.

Short-period comet 22P/Kopff was discovered photographically more than a hundred years ago, in August 1906. The comet was missed on its 1912 return, but was recovered in 1919 and recorded ever since. Its orbit has been slightly modified by passages close to Jupiter in 1942 and 1954, so that it currently takes 6.40 years to round the Sun (compared with 6.54 years early in the 20th century).

22P/Kopff was last seen in 2009, when it reached 10th-magnitude and developed a coma about 3’ across. At this year’s return, the comet will pass perihelion on October 25 and is expected to glow around magnitude +10.5.

Comet Kopff begins October in eastern Libra, very close to the planet Saturn. From there, it heads southeast through Scorpius and passes less than 1° north of Beta Scorpii on the evening of October 6. By the time it reaches perihelion, around month’s end, 22P/Kopff decorates a rather dim, sparse region of the constellation Ophiuchus.

Make sure the comet is near the top of your observing list because it sinks quickly into the southwestern horizon haze after darkness falls. Once you track it down, boost your telescope’s power past 100x to darken the sky further and increase the contrast.

Finder map – field width 30°, stars to magnitude +6.5.


Taurid Fireball
A Taurid fireball from the 2005 shower, over Toyama, Japan. The brightest star is Sirius and Orion is near upper center. Hiroyuki Iida / NASA

A great number of particles, called meteoroids, orbit the Sun. When the Earth passes through one of these meteoroid groups, its atmosphere sweeps many of them up. The particles then become meteors, as they hurtle to a swift, fiery destruction.

The visible effect comes not from the particle itself but from the trail of ionized air that the rapidly vaporizing particle creates. The vast majority of these projectiles from space are, fortunately for us, little bigger than grains of sand.

Each year, from mid-September to late November, the Earth plows through the meteoroid cloud left behind by periodic comet 2P/Encke and this produces the Taurid shower. There are two radiants to this stream, one 8° north of the other. The southern radiant peaks before dawn on October 10, and its northern cousin on November 12. Both radiants first appear in Cetus, drift across Aries, and move into Taurus in late October.

Taurid meteors are visible most of the night, but rates tend to be low – you should see about five shooting stars per hour, with numbers increasing after midnight. However, Taurids are slow moving and bright, which makes the display more impressive than their low numbers might suggest. The shower also produces occasional fireballs with spectacular trains, so it does not hurt to keep an eye on it.

Map – Taurids radiant position.

Constellation Orion
Orion is one of the most conspicuous constellations in the night sky, and the spot from which Orionid meteors appear to radiate. Akira Fujii

One of the best meteor showers to occur each year, the Orionids begin on October 2 and last until November 7. This display may produce 10 to 20 shooting stars per hour, but numbers vary greatly from year to year and the shower is above quarter strength for just two or three days centered on October 21.

This year, on Orionid maximum night, the waxing gibbous Moon sets around 1:30 A.M. local daylight time, leaving four hours of dark skies. The shower’s radiant rises before midnight and stands high in the south by 4 A.M. local daylight time.

As their name implies, Orionid meteors appear to come from Orion the Hunter, in the northernmost part of that constellation. Shower members are fast moving and can leave dusty trains, but they are not particularly bright so a dark observing site will be needed to see them well.

Like the Eta Aquariids in May, Orionid meteors result when the Earth encounters the stream of debris deposited by Comet Halley during its countless trips around the Sun. These small fragments of matter enter the upper atmosphere at a speed of 41 miles (66 kilometers) per second.

Map – Orionids radiant position.

Some meteors do not belong to any known shower. These are the sporadic meteors, caused by random bits of comet debris spread throughout the inner solar system. They appear randomly across the sky all year long.

In this month’s night sky, careful observers can expect around ten sporadics per hour during the morning hours and three during the dark evening.

Observing Aids

Northern Hemisphere’s Sky – This map portrays the sky as seen near 40° north latitude at 9 P.M. local daylight time in early October and 8 P.M. in late October.

Southern Hemisphere’s Sky – This map is plotted for 35° south latitude. It shows the sky at 8 P.M. local time in early October and 7 P.M. in late October.

Visibility of the Planets – The table provides general information about the visibility of the planets during the current month.

Phases of the Moon – This Moon Phase Calendar shows the Moon’s phase for every day in October.

Jupiter’s Moons – The diagram shows the positions of Galilean satellites on each day in October at midnight.

Sky Events

October 2 – 9 A.M. EDT: The Moon is 0.5° north of Aldebaran.

October 3 – 7 A.M. EDT: Asteroid 15 Eunomia is at opposition.

October 4 – 5:06 P.M. EDT: Last Quarter Moon.

October 8 – 5 P.M. EDT: The Moon is 0.7° south of Venus. 6 P.M. EDT: Mercury is stationary.

October 9 – 1 P.M. EDT: The Moon is 3° south of Mars. 5 P.M. EDT: Venus is 3° south of Regulus. 8 P.M. EDT: The Moon is 3° south of Jupiter.

October 10 – 5 A.M. EDT: The Southern Taurid meteor shower is at peak activity.

October 11 – 8 A.M. EDT: The Moon is 0.9° south of Mercury. 9:18 A.M. EDT: The Moon is at apogee, the point in its orbit when it is farthest from Earth.

October 12 – 1 A.M. EDT: Uranus is at opposition. 8:06 P.M. EDT: New Moon.

October 13 – 3 A.M. EDT: Asteroid 471 Papagena is at opposition.

October 15 – 11 P.M. EDT: Mercury is at greatest western elongation, 18° west of the Sun in the morning sky.

October 16 – 9 A.M. EDT: The Moon is 3° north of Saturn.

October 17 – 5 A.M. EDT: Mars is 0.4° north of Jupiter.

October 20 – 4:31 P.M. EDT: First Quarter Moon.

October 21 – 5 A.M. EDT: The Orionid meteor shower is at peak activity.

October 23 – 3 P.M. EDT: The Moon is 3° north of Neptune.

October 25 – 8 A.M. EDT: Asteroid 29 Amphitrite is at opposition.

October 26 – 3 A.M. EDT: Venus is at greatest western elongation, 46.4° west of the Sun in the morning sky. 4 A.M. EDT: Venus is 1° south of Jupiter. 6 A.M. EDT: The Moon is 0.9° south of Uranus. 9:01 A.M. EDT: The Moon is at perigee, the point in its orbit when it is nearest to Earth.

October 27 – 8:05 A.M. EDT: Full Moon.

October 28 – 3 P.M. EDT: Mercury is 4° north of Spica.

October 29 – 7 P.M. EDT: The Moon is 0.6° north of Aldebaran.

The information provided on this page is accurate for the world’s mid-northern latitudes. Finder maps for the five naked eye planets are plotted for 40° north latitude, but can also be used from other latitudes close to 40° north. Except the two all-sky maps, all other maps can be used no matter the latitude. Local time (local daylight time during summer) represents the time of the reader.