Best night sky events for August 2023

This month’s sky-watching information is provided by Chris Vaughan of Starry Night Education.

Wednesday, Aug. 2: Bright moon meets Saturn (overnight)

When the bright, very full moon clears the rooftops in the southeastern sky late Wednesday evening, Aug. 2, it will be shining a palm's width to the right (or celestial southwest) of the bright, yellowish planet Saturn.

While the duo won't be cozy enough to share the view in binoculars initially, the moon's steady eastward orbital motion, by about its own diameter every hour, will carry it closer to Saturn for those viewing them late at night or in westerly time zones.

Saturday, Aug. 5: Jupiter joins the evening sky (late night)

For observers at mid-northern latitudes, Jupiter (at lower left) will officially join Saturn in the evening sky starting around Saturday, Aug. 5, when it will start rising just before midnight local time. It will take an hour or so after it rises for the bright planet to clear the rooftops in the east. Hamal and Sheratan, the brightest stars of Aries, Jupiter's home constellation in 2023-24, will be shining above it.

On each subsequent night, the giant planet will arrive four minutes earlier, so it will be catching your eye in mid-evening by the end of September. Jupiter's best evening telescope-viewing period, when it will shine nice and high in the sky, will run from mid-autumn to early spring, 2024.

Monday, Aug. 7: Half-moon joins Jupiter (late night)

When the half-illuminated moon rises over the eastern horizon just before midnight on Monday, Aug. 7, it will be accompanied by the brilliant planet Jupiter. The duo will easily share the view in binoculars (orange circle) as they cross the sky together through the night.

By dawn Tuesday, the moon and Jupiter will be shining in the southeastern sky, making a nice photo opportunity. For a challenge, spot the moon in the daytime sky Tuesday morning and then use binoculars to look for Jupiter's pale dot shining a few finger widths below it (inset).

Tuesday, Aug. 8: Third quarter moon (at 12:28 a.m. PDT)

At its third (or last) quarter phase, the moon appears half-illuminated, on its western, sunward side. It rises around midnight local time, and then remains visible until it sets in the western daytime sky in the early afternoon. Third-quarter moons are positioned ahead of the Earth in our trip around the sun. About 3½ hours later, Earth will occupy that same location in space. The dark, moonless evening skies that follow this phase are the best ones for observing deep sky targets.

Saturday, Aug. 12: Perseid meteor shower peak (overnight)

The spectacular Perseid meteor shower, which runs between July 14 and September 1 every year, will peak after midnight in the Americas on Saturday night, Aug. 12. That means that the best time for seeing Perseids meteors in North America will be the hours before dawn on Sunday morning when the shower's radiant in Perseus will be high in the northeastern sky.

This is the most popular shower of the year, delivering as many as 100 meteors per hour at the peak. Derived from debris dropped by Comet Swift-Tuttle, many Perseids are extremely bright and leave persistent trails. This year the moon will not affect the shower. Its slim crescent will rise just before sunrise. To see the most meteors in any shower, find a safe, dark location with plenty of open sky, get comfortable, and just look up.

Tuesday, Aug. 15: Milky Way star clusters (all night)

With the moon out of the sky, the extra-dark evenings will be ideal to explore the countless knots and clumps of stars distributed along the Milky Way, many of which were included in Charles Messier's list of the sky's best deep sky objects.

Scan with binoculars to spot the objects, and then follow up with a backyard telescope at low magnification. Particularly good clusters include Messier 39 and the Cooling Tower Cluster (Messier 29) in Cygnus, the Wild Duck cluster (Messier 11) and Messier 26 in Scutum, the Sagittarius Star Cloud (Messier 24) and Ptolemy's Cluster (Messier 7) and the Butterfly Cluster (Messier 6) in Scorpius. ,

Wednesday, Aug. 16: New Moon (at 2:38 a.m. PDT)

On Wednesday, Aug. 16, at 2:38 a.m. PDT, the moon will officially reach its new moon phase. At that time our natural satellite will be located in Leo, 4.3 degrees northeast of the sun.

While new, the moon is traveling in space between Earth and the sun. Since sunlight can only illuminate the far side of the moon, and the moon is in the same region of the sky as the bright sun, it becomes completely hidden from view from anywhere on Earth for about a day (unless there's a solar eclipse, as there will be Oct. 14). On the evenings after the new moon phase, Earth's celestial night-light will shine as a crescent in the western evening sky.

Sunday, Aug. 20: Small constellations on high (evening)

On mid-August evenings, four small constellations sit high the southeastern sky, below the very bright star Vega. The easiest one to see is Delphinus, the Dolphin, which is composed of four medium-bright stars forming a small elongated diamond that joins to a straight tail star extending to the lower right (or celestial southwest).

Equuleus, the Little Horse is positioned about a fist's diameter below Delphinus. Diminutive Equuleus is the second to last constellation by size, after Crux, the Southern Cross. Sitting a generous fist's width above Delphinus is the next smallest constellation by area, Sagitta, the Arrow. And sweeping a palm's width higher will bring you to the stars of Vulpecula, the Fox. Except for the slightly larger fox, each of these small constellations will fit within the field of view of binoculars (orange circle). The Milky Way passes through Sagitta and Vulpecula, populating them with a variety of deep sky objects. The sky between those two constellations hosts a dark dust lane.

Monday, Aug. 21: The stinging scorpion (evening)

After dusk in the third week of August, the distinctive constellation of Scorpius, the Scorpion reaches its peak elevation over the southern horizon. The constellation's brightest star is orange-tinted Antares, the "Rival of Mars." Several medium-bright, white stars arranged in a roughly vertical line to the west of Antares mark the creature's claws on modern sky charts; however, the major stars of neighboring Libra used to perform that role. The rest of the scorpion extends to the south, curling eastward into the Milky Way, and terminating with the bright double star Shaula, which marks its poisonous stinger. Observers above mid-northern latitudes might not be able to see the southernmost stars of the constellation.

Thursday, Aug. 24: First quarter moon (2:57 a.m. PDT)

When the moon completes the first quarter of its journey around Earth on Thursday, Aug. 24, 2:57 a.m. PDT. Its 90-degree angle away from the sun will cause us to see the moon half-illuminated — on its eastern side.

At first quarter, the moon always rises around mid-day and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding the first quarter are the best ones for seeing the lunar terrain when it is dramatically lit by low-angled sunlight, especially along the terminator, the pole-to-pole boundary that separates the lit and dark hemispheres.

Friday, Aug. 25: Half-moon occults Antares (around 81 p.m. PDT)

On Friday evening, Aug. 25, observers can watch the bright, waxing gibbous moon occult Antares, the brightest star in Scorpius.

For the surrounding regions, the event will occur in a bright sky, or the moon will set during the occultation. The event can be seen with unaided eyes but will look best through binoculars and backyard telescopes.

Saturday, Aug. 26: Saturn at opposition (overnight)

A few hours after midnight on Saturday, Aug. 26 in the Americas, Saturn will reach opposition. You can see the creamy-yellow dot of the ringed planet all night long, surrounded by the rather faint stars of Aquarius.

Planets in opposition rise at sunset and set at sunrise because Earth is positioned between them and the sun. Tonight, Saturn will be at a distance of 814.6 million miles, 1.311 billion km, or 73 light-minutes from Earth. It will shine at magnitude of 0.41 — its brightest for 2023. While planets always look their brightest at opposition, Saturn's brilliance will be boosted by the Seeliger effect — backscattered sunlight from its rings. In a telescope (inset) Saturn's disk and rings will show maximum apparent diameters of 19 arc-seconds and 44 arc-seconds, respectively. Saturn's rings will be tilting more edge-on to us every month until the spring of 2025. Opposition is also the optimal time to view Saturn's moons through a backyard telescope in a dark sky.

Sunday, Aug. 27: Watch Algol brighten (at 8:32 pm PDT)

The star Algol (or Beta Persei) in the constellation of Perseus is among the most easy-to-monitor variable stars. During a ten-hour period that repeats every 2 days, 20 hours and 49 minutes, Algol dims noticeably and then re-brightens when a companion star with an orbit nearly edge-on to Earth crosses behind the much brighter main star, reducing the total light output we perceive.

Algol normally shines at magnitude 2.1, similar to the nearby star Almach in Andromeda. But while dimmed to minimum brightness, Algol's magnitude of 3.4 is almost the same as the star Rho Persei (ρ Per), which shines just two finger widths to Algol's lower right (or 2.25 degrees to the celestial south).

For observers in eastern North America, fully dimmed Algol will sit in the lower part of the northeastern sky Sunday, Aug. 27 at 11:32 p.m. EDT or 03:32 GMT on Aug. 28. Five hours later the star will shine at full intensity from a perch high in the eastern sky. Observers in more westerly time zones can see the latter stages of the brightening.

Wednesday, Aug. 30: Bright moon shines near Saturn (overnight)

When the nearly full moon clears the treetops in the southeastern sky after dusk Wednesday, Aug. 30, bright, yellowish Saturn will shine 4.5 degrees to the moon's upper right — close enough for them to share the view in binoculars (orange circle).

During the night, the moon's easterly orbital motion will carry it a bit farther from Saturn. Meanwhile, the diurnal rotation of the sky will drop Saturn below the moon before they set in the southwest an hour before dawn.

Thursday, Aug. 31: A full blue supermoon (at 9:36 p.m. EDT)

On Thursday, Aug. 31, at 01:36 GMT, which converts to Wednesday night at 9:36 p.m. EDT and 6:36 p.m. PDT, the moon will reach its full phase for the second time in August. When a lunar phase occurs on the first day or two of a calendar month, it will be repeated at month-end in what is colloquially known as a "Blue Moon." Blue moons occur once every two or three years and do not display any unusual coloration.

The moon will be full only 9.5 hours after its perigee, making this the largest full moon in 2023, and a supermoon — appearing about 7% larger and shining a bit brighter than average (red ring). The world will experience higher tides due to this full moon's proximity to Earth.