Skylights: August 2024

August 3 sees the last sunset during the 8:00pm hour until May 16, 2025. The Sun passes into Leo on the 10th, where it will spend the next 27 days. It is closest to the constellation's brightest star, Regulus, on the afternoon of the 22nd, coming to within just 0.2° of the star.

On the 18th, the Sun is halfway in declination between solstice and equinox: +12° 43’ 09.

The 20th sees the last 6:00am sunrise until April 19, 2025.

By mid-August, it has become noticeable that the Sun is no longer near its high solstice perch, at +23.4° north declination. On the 18th, its northerly declination is halved, to +12.6°. From now on, it will seem to accelerate quickly southward towards the equinox, just 35 days away.

The Moon is new, in Cancer, at 7:13am on August 4, marking the beginning of Lunation 1257. Due to the Moon’s location well north of the ecliptic, there’s a fairly good opportunity to spot a young (13 hour) crescent just after sunset. The Sun sets at 7:59pm, and the 0.3% illuminated crescent Moon is down less than a half hour later. A low horizon, clear and transparent sky, and large binoculars or telescope will be needed for this observing challenge.

There is a dramatic pairing of the 2.2% waxing crescent Moon and Venus on the 5th, and on the 9th, the waxing crescent Moon is 4.8° west-northwest of Spica, in Virgo.

The Moon is first quarter, in Libra, at 11:19am on the 12th. The following evening, at 11:00pm, it lies 1.5° west-southwest of Antares, in Scorpius.

The Full Sturgeon Moon occurs at 2:26pm on the 19th, and rises at 7:58pm, in Aquarius.

Just past full, the Moon is 0.3° south of Saturn on the 20th. It passes 2.6° east-northeast of Neptune the following night, on the 21st.

One of the best Moon-Pleiades conjunctions of the year occurs just as the Moon rises on the 25th, with the last quarter Moon occulting some of the outer stars in the southeastern portion of the cluster.

The waning crescent Moon appears 6.0° northeast of Mars on the 28th, and just before dawn, 3.4° northeast of the open star cluster M35 in Gemini.

The waning Moon is then 5.1° north-northwest of Jupiter on the 27th, 4.1° west-northwest of open cluster M35, in Gemini, on the 28th, and 2.7° southwest of Pollux on the 30th.

Finally, on the 31st, the 6.7% illuminated waning crescent Moon is 3.4° north-northeast of the Beehive cluster in Cancer, M44.

Following a fairly good evening appearance of Mercury in July, the innermost planet becomes difficult to view in early August due to its low position, setting just 30 minutes after sunset.

Mercury returns to the morning sky for its best dawn apparition of the year after passing inferior conjunction on the 18th.

By the 23rd, Mercury rises 30 minutes before sunrise, 60 minutes on the 27th, and 100 minutes before sunrise on the 31st. The final week of the month is the best time to view Mercury’s crescent phase with a telescope.

Although Venus is gradually increasing in separation from 15° to 24° east of the Sun over the course of August, in a peculiar circumstance resulting from its separation and the earlier sunsets, the planet itself actually sets earlier each night in August, from 8:52pm to 8:17pm. It does, however, remain visible after sunset for eleven more minutes at the end of the month (58 minutes) than on the 1st.

Gazing at Venus through a telescope low in the sky and through bright twilight will not reveal much. Its gibbous disk shows 96% in early August, and gains only a fraction of an arcsecond in apparent diameter at the end of the month, when its illuminated phase reaches a still barely discernible 91%, at just under eleven arcseconds.

In August, Venus appears best when it is paired with other celestial objects, especially when using binoculars or a low-power, wide-field telescope. On the 5th, the 2.2% illuminated waxing crescent Moon is just 0.4° north-northwest of the planet, and the entire first week of the month finds Venus passing close to Regulus, with the pair being separated by just 1.0° on the 4th.

Mars spends August moving eastward through Taurus, rising just after 1:00am on the 1st, and a few minutes past midnight at the end of the month.

Mars is still rather distant, ranging from 1.60 to 1.44 au during August, presenting a gibbous disk just over 6 arcseconds across. What it lacks in telescopic splendor, it makes up for in naked-eye and binocular viewing as it traverses the celestial bull.

During the first week of August, Mars is located about 5° degrees from the red giant star Aldebaran. Mars is currently shining at the same magnitude as Aldebaran, giving the star a temporary twin.

The Red Planet’s best performance of August occurs during mid-month, when it passes just 0.3° northwest of Jupiter on the 14th. On this date, Jupiter is 3.5 more distant from Earth than Mars, the light of the latter taking 12.7 minutes to reach us, while Jupiter is 44.7 light minutes away.

A view through any telescope presents the observer with six solar system objects within easy view, as Jupiter's four Galilean satellites will all be visible in the same field of view.

The two planets remain close enough to be observed together in binoculars for several days before and after conjunction.

Mars is just 1.1° north of the Crab Nebula, Messier 1, in Taurus on the 26th and 27th. On the 26th, the waning crescent Moon appears 6.0° northeast of Mars.

Jupiter joins the ranks of the evening planets in August, but only at the end of the month, when it rises at 11:45pm. Early in the month, observers will have to wait at least until 1:30am to see the giant planet enter the northeastern sky, in Taurus.

In a notable close conjunction, Jupiter is joined by Mars mid-month, coming to within just 0.3° separation on the 14th.

Saturn is in eastern Aquarius, and rises just before 10:00pm at the beginning of the month, and by the end of the month, it is already above the horizon as twilight fades.

Beginning on the 18th, Saturn and Venus are above the horizon in the evening sky at the same time.

The just-past-full Moon is 0.3° south of Saturn on the 20th.

If you have a larger telescope, watch Saturn's moons as they transit and are eclipsed by the planet: Just after midnight on the 1st, Titan passes over Saturn’s southern limb, followed by Dione and its shadow. On the 2nd-3rd, Rhea and its shadow transit Saturn. On the 3rd, Dione and its shadow can be seen exiting Saturn’s eastern limb. Just before dawn on the 5th, Rhea and Dione drop into Saturn’s shadow nearly simultaneously. Dione emerges from behind Saturn’s western limb on the morning of the 8th. Titan briefly dips behind Saturn’s northern limb after midnight on the 9th. Rhea, Dione, and their shadows cross Saturn’s disk on the 11th-12th, followed shortly after by the disappearance of Tethys behind Saturn’s shadow. Tethys and its shadow pass over Saturn just below the ring plane early on the 13th. Tethys can be seen passing completely behind Saturn on the 14th, and passing in front of Saturn, with its shadow, again after midnight on the 15th. Tethys can be seen passing completely behind Saturn again on the 15th-16th, followed shortly afterwards by the disappearance of Dione. Tethys then crosses in front of Saturn on the 16th-17th.

At midnight on the 17th, Titan can be seen hovering just below Saturn’s south pole. Rhea and Dione emerge from behind Saturn on the 17th-18th. Beginning at midnight on the 21st, Rhea and its shadow pass over Saturn. Dione and shadow transit Saturn on the 22rd-23th. On the 24th, Titan can be seen hovering just over Saturn’s north pole. Dione passes into eclipse after midnight on the 27th. On the following evening, Tethys reemerges from behind Saturn’s western limb. Tethys passes into eclipse on the morning of the 29th. Dione re-emerges from eclipse before midnight on the 29th, followed by Rhea going into transit. One final eclipse of Tethys occurs on the 31st, immediately followed by a transit of Dione.

Uranus, the third planet in Taurus, becomes an evening planet in August, rising before midnight starting during the second week, and reaching its point of western quadrature on the 19th.

The planet lies within easy reach of binoculars just 5° south-southwest of the Pleiades cluster. To begin the journey, move 4.3° directly south from the Pleiades to find a pair of 6th magnitude stars, 13 and 14 Tauri, which lie on a 20 arcminute line (⅔ of the apparent diameter of the Moon) that lie in a nearly east-west orientation. 13 Tau, the westernmost of the pair, is slightly brighter, and is the jumping-off point to locate Uranus. Uranus is a magnitude 5.7 pale blue-green object to the east-southeast of 13 Tau, which is the same brightness. The distance closes from 1.3° on August 1st to 1.0° on August 31st. 

Neptune is in Pisces, and rises a few minutes later than Saturn, being located along the ecliptic about 12° east of the ringed planet. 

From the Circlet asterism of Pisces, start at lambda, and go 5.3° southeast.

A line drawn from 33 Piscium through 29 Piscium, and extended another 1.6° northward, brings you to the magnitude 7.7 ice giant.

The waning gibbous Moon is 2.6° east-northeast of Neptune on the 21st.

1 Ceres is located in the center of the Teapot asterism of Sagittarius, and is at its best viewing position in early evenings in August. It dims from magnitude 7.8 to magnitude 8.4. Its position rather low in the sky and in a fairly dense section of the Milky Way, will make identifying it a challenge. Despite its relatively bright magnitude, it will require more than binoculars to locate. Unless you are located under a truly dark and transparent sky, a 4-inch telescope with medium magnification is likely to be needed to spot the dwarf planet.

The waxing gibbous Moon is 2.5° northwest of Ceres on the 15th.

At the beginning of August, Ceres is located about 1.8° north of the globular cluster M70, and as it completes its retrograde loop at the end of the month, Ceres is about 1.5° north of the globular cluster M69. 

2 Pallas is moving southeastward just to the east of the head of the serpent, Serpens Caput, making an 8° radius arc to the southwest of Kornephoros (beta Herculis). The 10th magnitude asteroid should remain fairly easy to observe in small telescopes during moonless nights.

Asteroid 7 Iris is at opposition on the 4th, at a distance of 3.10 au and magnitude 8.3, in Aquarius. It is located about 3.0° north of planetary nebula Caldwell 55, the Saturn Nebula, in Aquarius. On the 18th-19th, the asteroid is just 0.4° north 0f Albali (epsilon Aquarii).

Comet 13P/Olbers remains visible in the northwestern sky after dusk. As our distance increases to over 2 au from the comet, it dims to an expected 10th magnitude. While this isn’t impressively bright, this comet is notable for being in a favorable position for observation as it travels east-southeastward from Ursa Major and through Coma Berenices.

At the beginning of the month, the comet appears near the easternmost pair of the Three Leaps of the Gazelle, with the comet pointing due east of the stars. On August 14-18, it traverses the Coma Star Cluster (Melotte 111).

On August 25th it lies just 0.5° northeast of the galaxy M64, and on the 30th, it lies 1.0° north-northeast of the globular cluster M53, and 1.7° northeast of Diadem (alpha Comae Berenices).

The most significant active meteor shower in August is the Perseids, which generally shows activity from mid-July through the end of August, with peak occurring around August 11th-12th, when it is possible to see over 50 meteors per hour. The meteors appear to originate from a point in northern Persus, which is circumpolar, so meteors can usually be seen at any time during hours of darkness. On the night of peak activity, a waning crescent Moon sets just before 11:00pm. Increasing moonlight interferes on subsequent nights, but the nights leading up to the 11th are more favorable.