Skylights: October 2025

October brings some of the most pronounced seasonal changes to our nighttime skygazing. The sounds and smells of summer have passed on, But, with the distinct scent of autumn leaves and the absence of the frogs, katydids, and all but perhaps few enough crickets to count, the still nights of autumn are getting longer, cooler, and quieter.

In the west, we see Arcturus, the brilliant star that foretells the coming of spring, and has been a presence in our evening sky since, is now low in the sky, soon to trade places to the morning sky.

As we continue to anticipate the once-in-80-year outburst of the Blaze Star, T Coronae Borealis, we have less time to observe the star during October, as it is getting lower in the northwest after sunset, sets during the mid-to-late evening, and doesn’t rise before the onset of morning twilight until about a week into November.

Looking towards the south, we find our gaze turning away from the glow of the Milky Way, and towards the dimmer constellations of autumn. While Capricornus, Aquarius, Cetus, and Pisces are relatively devoid of bright stars, one notable exception is Pisces Austrinus, which gives us the lone first magnitude star, Fomalhaut, a class A3 main sequence star that lies just 25 light years away. Lying 59° east-southeast from the next-nearest first magnitude star, Altair, Fomalhaut is the most isolated of the first magnitude stars in our sky from our latitude of about 42° north.

This year, Fomalhaut is part of a distinct but temporary “autumn triangle” asterism along with Diphda (beta Ceti) and Saturn.

Moving north from Fomalhaut, we find the Great Square of Pegasus, the symbolic asterism of autumn, moving high overhead as the evening hours advance. To its east lies Andromeda with its showpiece spiral galaxy M31, which from under a reasonably dark sky, is the most distant object that can be seen with the unaided eye, the combined light of its trillion stars being 2.5 million years old by the time it reaches us.

The prominent Summer Triangle, a fixture of our evening sky for much of the year, remains high overhead, but it has now crossed the meridian and occupies the western part of the sky, where it will reside until it falls out of view in January.

Although the central bulge of the Milky Way and its bright clusters and nebulae are moving out of view, a large stretch of our home galaxy can still be seen overhead and to the northeast, spilling out of the constellations Cygnus, Lacerta, Cepheus, Cassiopeia, Perseus, and Auriga. A pair of binoculars on a moonless night provides a rewarding adventure.

Late night observers will take note that the winter constellations, including the mighty Orion, become visible around midnight in October. If you enjoy exploring this part of the sky, but aren’t quite ready for the cold winter nights, October mornings present a good opportunity.

Finally, the pre-dawn sky shows us the return of the spring constellations, as Leo, Hydra, and Ursa Major can now be seen in the east.

Our own solar system presents some exciting events in October. Jupiter enters the evening sky, the Moon occults some bright stars, including the Pleiades, and we have some comets and meteors to watch for. 

Sun

At about 4:00am EDT on the 5th, Earth reaches the point of 1.0 au distance to the Sun. We will remain closer than 1.0 au from the Sun until April 4, 2026.

Although not visible to us, the Sun is at the same right ascension as Spica, in Virgo, on the 16th. The 1st magnitude star is 1.9° south of the Sun’s position on this afternoon.

October 17 gives us the final sunset in the 6:00pm hour. The Sun will not set this late again until March 8. October 17 is also our last day with eleven full hours of daylight. The next one will be February 24, 2026.

The Sun is at its halfway point between equinox and solstice (declination -12° 43’ 09”) on the 26th. The Sun remains south of this line of declination until February 15, 2026.

After a 44.5-day trek through Virgo, the Sun enters Libra at 4:00am on the 31st, where it will spend the next 23 days.

Moon

To start the month of October, the 69.9% waxing gibbous Moon is just 0.8° east-southeast of Pluto on the 1st. This pairing would be quite an observing challenge, as the Moon is about 16 billion times brighter than Pluto. Capturing it photographically with a sensitive imaging device is a bit more feasible. If you can observe the two objects simultaneously, consider that Pluto’s light took four hours 51 minutes to reach us, and that the distant dwarf planet is 13,329 times the distance from Earth as the Moon.

October 4th is International Observe the Moon Night, but this year we’ll be celebrating on Sunday the 5th. Watch the 98% waxing gibbous Moon rise at 5:34pm over the Seekonk River with Skyscrapers members and friends from Blackstone Field on the East Side of Providence, adjacent to the Narragansett Boat Club on River Drive. Bring a telescope, binoculars, or a camera, and enjoy the moonrise with us. The Moon will be just 2.2° north-northwest of Saturn on this evening. A few hours later, early on the morning of the 6th, the Moon is 1.8° north-northwest of Neptune. Throughout the evening, you should be able to observe all three objects simultaneously in a small telescope with a wide field of view.

The Moon is full at 11:48pm on the 6th, marking 2025’s Harvest Moon, as October’s full Moon is 14.5 hours closer to the equinox than September’s full Moon. The Harvest Moon is in Pisces, and rises at 5:57pm, when the Sun is still above the horizon, making this full Moon rise a very favorable one to photograph.

We have missed the last several occurrences of it, either because it happens during daylight for us, or the Moon is below the horizon, but October gives us our first nighttime view of the Moon occulting the Pleiades.

The first of the brighter members, Celaeno (16 Tauri), is occulted beginning at 11:36pm on the 9th. Electra (17 Tauri) is occulted about three minutes later. At 11:54pm, Taygeta (19 Tauri) dips behind the bright limb of the Moon, followed by Maia (20 Tauri) at 12:04am on the 10th.

Electra emerges at 12:19am, followed by Celaeno at 12:39am, Taygeta at 12:58am, and Maia at 1:08am.

The Moon reaches its most northerly declination during lunation 1271 on the 12th, at +28.27° in the non-zodiacal constellation Auriga.

Last quarter Moon, in Gemini, is at 2:13pm on the 13th.

The 3.8% crescent Moon rises with Venus, 4.1° to its east-northeast, on the 19th, creating one of the more stunning sights in the sky.

Attempt to spot a very old Moon on the 20th. The 1.0% illuminated crescent will be completely above the horizon starting at 6:14am. Using Venus as a guide, draw a line down to the horizon, and move one degree to the right.

Lunation 1272 begins with the new Moon at 8:25am on the 21st.

The Moon reaches its most southerly declination for lunation 1271 on the 26th, at -29.25° in Sagittarius.

There are two more occultions of relatively bright stars by the waxing Moon in late October.

On the 27th, the 3.4% waxing crescent Moon occults magnitude 3.3 tau Sagitarii, the easternmost star in the teapot asterism of Sagittarius, beginning at 7:39pm. The star, a K class orange giant star that lies about 120 light years away, reappears at 8:44pm from the bright limb of the Moon, beyond Mare Crisium.

The first quarter Moon is at 12:21pm on the 29th, in Capricornus. 

On the 30th, the 63.7% gibbous Moon occults Deneb Algedi, a magnitude 2.8 eclipsing binary star that lies at a distance of 39 light years with a period of 1.02 days, dimming by 0.2 magnitudes. The star disappears at 9:09pm and reappears 50 minutes later.

Mercury

Mercury spends October in its least favorable evening apparition of the year for northern hemisphere observers. While it reaches its maximum elongation of 23.9° east of the Sun on the 29th, it never spends more than an hour above the horizon following sunset, during which time it remains low over the southwestern horizon.

Due to Mercury’s inclination angle keeping it south of the ecliptic, which is already at a low angle of incidence during October evenings, the planet doesn’t gain considerable elevation over the horizon, but continues to appear further towards the south each evening. 

If you’re searching for Mercury on the 2nd, you may notice magnitude 1.0 Spica, which lies 1.7° to the south-southwest of the magnitude -0.5 planet.

The innermost planet joins the Moon and Mars, with the three appearing in a line on the 23rd. You’ll be able to locate the 5.3% crescent moon first, then, with binoculars, go 3.9° to the north-northeast, or right and slightly above, to find Mercury. Then, continue along this direction another 3.0° to locate Mars. 

Venus

Venus is now over 1.5 au from Earth, moving along the far side of its orbit towards superior conjunction in early January. It is visible low in the eastern sky before sunrise, rising about 2½ minutes later each morning. Its gibbous disk has shrunk to just about 11 arcseconds, but the planet still retains its brilliance at magnitude -3.9.

Venus crosses into Virgo on the 9th.

On the 19th, the super slim crescent Moon is just 4.1° southwest of Venus.

Mars

All but lost in the twilight glow in October is Mars. The Red Planet, now over 2.35 au away, sets about an hour after sunset throughout the month. Mars crosses from Virgo into Libra on the 4th.

On the 14th, it is 0.5° south of the wide double star Zubenelgenubi (alpha Librae). 

Mercury joins Mars during the third week of the month, appearing as close as 2.0° to its south on the 19th and 20th. 

Jupiter

Jupiter becomes an evening planet in October, rising before midnight for the first time on the 6th.

On the 7th, the giant planet passes in front of NGC 2420, an open cluster containing several hundred stars in an area smaller than ⅓ the apparent diameter of the Moon. None of the cluster’s member stars shine brighter than 11th magnitude, so they will be all but washed out by Jupiter’s glare in a small telescope, but viewing under medium-to-high magnification with a large aperture telescope should clearly reveal Jupiter moving amongst a rich star field.

The 45% waning crescent Moon joins Jupiter, 4.5° to its northeast, on the 14th. The two bright objects will rise nearly simultaneously out of the east-northeast at 11:32pm on the 13th, with the Moon in line with the twin stars Castor and Pollux.

Jupiter is at minimum illuminated fraction, 99.1%, on the 15th. Given Jupiter’s equatorial oblateness, detecting the subtle gibbous phase isn’t all that apparent; what you may be able to see is the darkening of its eastern limb, compared with the sharp definition of its sunlit western limb. The effect is usually more pronounced in images taken of the giant planet through larger telescopes.

Minimum illumination of Jupiter (or any outer planet) occurs when the Sun-planet-Earth angle, that is, the angular separation of the Sun and Earth as seen from the planet, is at its greatest. As seen from Jupiter, Earth and Sun are separated by just under 11.1.° This maximum separation angle also coincides, roughly, with the quadrature angle as seen from Earth. There are slight differences in the timing of these two events due to the orbits of Earth and Jupiter being inclined with respect to each other, and also them not being perfect circles, so the date of Jupiter’s quadrature happens about a day and a half later, on the 17th. This is when Jupiter appears to be 90° west from the position of the Sun. Western quadrature also marks the time when an outer planet transits the local meridian at sunrise, making this the beginning of the most favorable conditions for observing Jupiter.

On the 20th, Jupiter crosses east of the line connecting Pollux and Procyon, and will therefore appear outside of the Winter Hexagon asterism for the first time since February. It won’t remain outside for long, however, as the planet goes into retrograde motion and will cross back into it in early December.

Moons of Jupiter

Watch Io overtake Europa, just before the pair crosses over Jupiter’s western limb at 4:00am on the 4th.

Jupiter rises apparently moonless, except for Callisto, on the 5th, with Io and Ganymede transiting, and Europa occulted. Io’s transit ends at 12:50am, followed by Europa coming out of occultation at 1:32am, then Ganymede comes out of transit at 2:44am.

A close pairing of Io and Europa to the west of Jupiter appears on the 8th at 3:50am, after which the moons will appear in order of their respective orbital radii from the planet. Later on the 8th and overnight into the 9th, Ganymede and Europa appear close together for several hours.

The moons appear in two tight pairs to the east (Europa and Ganymede) and west (Callisto and Io) on the 10th. Io and Europa track together on the evening of the 10th, initially joined by Ganymede, and continue to move together as they both transit Jupiter heading into twilight. The shadows of both moons transit Jupiter simultaneously from 4:40am to 6:52am on the 11th.

On the 12th-13th, Io and Ganymede have simultaneous shadow transits from 11:08pm to 1:26am. Io and Ganymede themselves transit in turn, from 12:48am to 2:44am and 3:30am to 6:48am, respectively. Soon after Io emerges, Europa emerges from occultation at 3:06am. 

Another close pairing of Ganymede and Europa is visible in the morning of the 16th.

On the 18th-19th, Callisto transits the planet, emerging at 12:42am, and catches up with Io, which goes into eclipse at 3:48am just as the pair of moons get close near Jupiter’s eastern limb.

Early in the morning of the 20th, Io and Ganymede cast their shadows on Jupiter simultaneously, with Io’s shadow transiting from 2:12am to 5:28am, and Ganymede’s from 1:02am to 3:18am. Europa goes into eclipse at 1:18am, and Io transits Jupiter from 2:22am to 4:36am.

On the 31st and into the 1st, the moons appear in their order of orbital radius, extended to the east of the planet.

Saturn

October’s evening skies offer Saturn as the only bright planet in an optimal position for viewing. Moving retrograde through Aquarius, the ringed planet can be found in the southeastern sky after twilight fades.

On the 5th, the nearly full Moon is just 2.2° to the north-northwest of Saturn, and with a wide field telescope, you’ll be able to see not just the Moon and Saturn, but also Neptune, which is 2.0° to the east of the Moon.

Moons of Saturn

The last of Titan’s shadow transits visible to us begins at 12:26am on the 6th, when the shadow of Saturn’s giant moon grazes the northern limb of the planet, departing after 1:42am. As this is still relatively close to Saturn’s opposition, there is also a coinciding transit of the moon itself, beginning at 9:25pm on the 5th, ending at 1:44am on the 6th.

While the next shadow transit of Titan will not occur until 2038, the moon itself continues to transit the planet's disk a few more times, and keen observers with larger instruments, exceptionally good observing conditions, and sensitive image equipment may be able to track Saturn’s smaller, inner  moons as they continue to cast shadows across the planet’s cloudtops throughout the next several months.

Titan enters occultation at 6:57pm on the 13th, during nautical twilight. It remains behind Saturn and in eclipse until 12:50am.

Another transit of Titan, without its shadow, takes place on the 21st, beginning at 6:45pm. The moon takes nearly six hours to cross Saturn’s northern equatorial belt.

On the 29th, Titan emerges from occultation at 10:22pm while partially eclipsed. It comes out of eclipse a few minutes past midnight on the 30th.

Titan comes out of eclipse at 00:00pm on the 29th.

Uranus

Uranus, moving retrograde (westward) through Taurus, remains easy to locate about 4° from the Pleiades cluster. To aid your journey to the seventh planet, locate the pair of sixth magnitude stars 13 and 14 Tauri, oriented roughly west-to-east and separated by ⅓°. The pair can be located by drawing a line from zeta Persei, through Alcyone (eta Tauri, the “center” star of the Pleiades), and continuing south-southwestward. Now move east, and the first 6th magnitude object you will see is Uranus. In early October, the planet is 2.6° east of 14 Tauri, and Uranus moves 1.0° closer to the star on the 31st.

Neptune

Neptune is well-positioned in Pisces, and easy to locate thanks to its proximity to Saturn.

At magnitude 7.7, Neptune is visible in the same binocular field of view as Saturn. In early October, the planetary pair is separated by 3.2°, but due to Saturn’s higher rate of apparent motion in the sky, the separation increases to 4.1° to the west of the distant planet by month’s end.

The nearly full Moon is close to Neptune on the 5th-6th, passing as close as 1.8° to its north-northwest just past midnight.

As Saturn drifts farther west, it may be helpful to use some closer guide stars to locate Neptune. To the east of Saturn, by about 2°, find a quadrilateral of stars, about 2.6° long by 0.9° wide, oriented roughly north-south. The stars are, clockwise from north, 29, 27, 30, and 33 Piscium, all of which are 5th magnitude, with the exception of 30 Psc, which is slightly brighter at 4th magnitude. Neptune is just under 2° north of the northern pair of stars.

At the beginning of the month, draw a line diagonally through the quadrilateral, north-northeastward from 30 through 29. Neptune will be about 1.8° along this line, and slightly east, through October 12, when it crosses the line and will be slightly west. During the last week of October, it lies close to the line extended from 33 through 29.

Minor Planets

Two of our solar system’s dwarf planets are at opposition in October.

Ceres is at opposition on the 2nd, in Cetus. The asteroid belt’s largest and first discovered object is just under 2 au away, and shines at a fairly bright magnitude 7.6, putting it within reach of binoculars for the remainder of the month. Around the time of its opposition, it is 2.5° west of eta Ceti, a magnitude 3.5 class K orange giant star that is 125 light years away. Ceres moves west-southwestward at a rate of about 0.2 degrees per day. 

On the 3rd and 4th, Ceres passes within 0.4° of the nearly face-on spiral galaxy NGC 309. Although rather dim in our telescopes, this seemingly unremarkable 13th magnitude galaxy is quite large and luminous, its light traveling about a quarter of a billion light years to reach us.

On the 15th, Ceres passes 0.5° north of NGC 255, an 11.8 magnitude spiral galaxy about 60 million light years distant. On the 15th and 16th, it also lies 1.0° north of the planetary nebula Caldwell 56 (NGC 246), the ghastly shell of a dead star that lies 1600 light years away and fluoresces at 8th magnitude.

By the end of October, the large asteroid will have dimmed to magnitude 7.9, and lies 4.5° southeast of magnitude 3.6 iota Ceti. 

At an enormous distance of 94.565 au, dwarf planet Eris reaches opposition on the 18th. It is located in Cetus, about 0° southwest of Piscium, and 1/4° south of the celestial equator, placing it in an ideal position for observation with imaging equipment capable of resolving its 18.6 magnitude speck.

Pluto is visible in the early evening, in Capricornus. It can be located 1.9° south-southwest of the magnitude 5.9 star 4 Capricorni, and 3.0° east-southeast of globular cluster Messier 75. At a distance of  34.950 au, Pluto shines at a dim 14.5 magnitude.

2 Pallas, although dimmed to 10th magnitude, is still well-positioned to observe, located just a few degrees from theta Aquilae. It is moving in a southeasterly path that takes it closest to the star, 2.2° to its northeast, on the 22nd.

4 Vesta spends October moving eastward through southern Ophiuchus at a rate of nearly 0.5° per day. Although it is rather low in the southwest in the early evening, its magnitude 7.8 glow and its path near to some bright stars and deep sky objects make it worth tracking. 

During the first week of October, Vesta is north of Antares, within the same binocular field of view as the red supergiant in Scorpius. On the 6th, it is 0.6° of magnitude 4.5 omega Ophiuchi. It passes by a pair of 9th magnitude globular clusters, which will only be visible to observers using larger aperture telescopes; on the 15th and 16th, it is 0.5° north of NGC 6235, and on the 21st it is 0.5° north of NGC 6287. 

Asteroid 6 Hebe, which passed its opposition in late August, remains visible with larger binoculars and small telescopes at 8th magnitude. It is stationary in early October, then resumes its prograde (eastward) movement near the border of Aquarius and Piscis Austrinus. With a lack of relatively bright stars nearby, use Fomalhaut (alpha Piscis Austrinus) as a starting point to locate it. From the 1st magnitude star, move 4.6° northwest to magnitude 4.2 epsilon Piscis Austrinus, then move about the same distance and direction, yet ever so slightly south, to magnitude 5.50 49 Aquarii. Hebe is within the same binocular field of view, within 2.5° of the star throughout the month. On the 21st and 22nd, it passes within 0.2° north of the star. If you have a large telescope, you may be able to spot Hebe passing in front of NGC 7252, a pair of merging galaxies that lie 220 million light years away, on the 25th.

Comets

C/2025 R2 (SWAN)

Discovered on September 11, 2025 in images captured with the Solar Wind Anisotropies (SWAN) instrument onboard NASA’s Solar and Heliophysics Observatory (SOHO), Comet C/2025 R2 SWAN is in our evening sky throughout October, hovering around 9th magnitude before fading rapidly as it moves out of the inner solar system.

On the 2nd, it is just 1.0° from Zubenelgenubi (alpha Librae).

On the 13th, it lies 0.8° south of Sabik (eta Ophiuchi), and on the 17th, it is 1.0° south of Messier 16 in Serpens.

The comet is nearest to Earth on the 19th, at a distance of 0.261 au, during which time it is moving at a rate of 4.7° per day 

C/2025 A6 Lemmon

Comet C/2025 A6 Lemmon is visible in the northern sky during October.

On the 6th and 7th, it is located close to Tania Australis (mu Ursae Majoris), the southern star of the middle pair of the Three Leaps of the Gazelle asterism. This part of the sky sets early in the evening, but is once again easy to view in the northeast after 1:00am. The comet may be visible in binoculars, at about magnitude 8.

It passes 0.2° north of Cor Caroli (alpha Canum Venaticorum) near the bright spiral galaxy Messier 94 on the 16th.

On the 18th, the comet passes close to Caldwell 29 (NGC 5005), a spiral galaxy that lies 75 million light years away in Canes Venatici.

On the 19th and 20th, it is within the same binocular field, or about 6° from the globular cluster Messier 3, and may be as bright as 5th magnitude.

Comet Lemmon is closest to Earth on the 20th, at a distance of 0.596 au.

On the 21st and 22nd, it is in the vicinity of Izar (epsilon Bootis). The comet then moves into Serpens, moving southwestward at 4.0° per day, passing just over 1° south of beta Serpentis on the 26th.

Comet Lemmon is at perihelion on November 8, at a distance of 0.530 from the Sun.

3I/ATLAS

Another comet of note is moving through the sky in October, although this one will remain rather dim. Comet 3I/ATLAS is worth mentioning because it is only the third known object that originated outside of the solar system. It was discovered on July 1, 2025 using the 50cm Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile. The computed hyperbolic orbit of the comet shows that it is moving too fast to have originated in the Oort Cloud, and will eventually leave the solar system after it passes perihelion on October 29th.

At perihelion, its closest distance from the Sun will be 1.356 au, and it will be traveling at a Sun-relative velocity of 68.3 kilometers – that’s approximately the length of Rhode Island, from north to south – in one second.

At this time, it is expected to remain fairly dim, beyond the visual limit of most of our backyard telescopes, at 14.7, although our electronic eyes should be able to resolve it fairly easily.

As the comet is moving retrograde through the inner solar system (and across our celestial sphere), its position in Virgo during October makes it difficult to observe due to its proximity to the Sun, but by early November it becomes visible low in the southeastern sky before the onset of astronomical twilight. The comet appears just over 1.0° from Venus on the 31st and November 1st.

The closest 3I/Atlas gets to Earth is 1.797 au on December 19th, when it will reside near Regulus in Leo, and likely be dimmer than magnitude 15.

October Meteors

October brings a return of notable meteor activity after a several week lull following the Perseids in August.

The Orionids, which are remnants of history’s most famous comet, Halley, are active throughout October and into early November, with peak activity on the night of October 22-23, when a favorable 1.9% crescent Moon sets during twilight. As many as 20 Orionids per hour can be seen on peak night.

Additionally, the Taurids, a pair of meteor streams left by 2P/Encke, are also active from mid- October into November. While they are both relatively low-rate showers that peak in early November, they are known to be slow-moving and can produce fireballs throughout the duration of their activity, so keep watching for them.