Skylights: August 2023

August 2023  :  Jim Hendrickson

August 4 is the last sunset in the 8pm hour. The next 8pm sunset won’t occur until May 16, 2024.

After spending 21 days in Cancer, the Sun enters Leo on August 11. On the 23nd, it is located 0.2° south of Regulus. This comes just a few hours after it reaches the midpoint in declination between the Tropic of Cancer and the equator, declination, 11°43.1’’.

On August 22, the Sun rises after 6am for the first time since April 18. 

The Full Sturgeon Moon occurs at 2:31pm on the 1st. The Moon rises in the southeast, in Capricornus, at 8:36pm. This is the first of two Full Moons in August. 

Typically, the Harvest Moon follows the August Sturgeon Moon, but this year, the Sturgeon Moon occurs early enough in the month, that the following full Moon occurs more than one-half of a lunar synodic month from the September equinox

The second full Moon of August, a blue Moon, occurs at 9:35pm on August 30. This full Moon occurs in Aquarius, and rises at 7:36pm, about 14 minutes after sunset.

Besides being a blue Moon, this full Moon is notable for occurring within days of the opposition of Saturn, which you may notice hovering just 4° west-northwest  of the Moon as it rises that evening.

Following the Sturgeon Moon, follow the waning Moon as it passes 3.7° south of Saturn after midnight on the 3rd, and 4° east of Neptune early on the 4th.

Last quarter occurs on the 8th, and will be placed just 1.7° north of Jupiter. The following morning, the waning crescent Moon will be 2.5° southwest of the Pleiades cluster in Taurus.

On the morning of the 15th, an opportunity exists to observe a very old, 28.7-day, 0.9% illuminated crescent Moon in Cancer, 5° east of the Beehive Cluster, M44.

New Moon occurs on the 16th, marking the start of Brown Lunation Number 1245. The 2-day waxing crescent appears 1.0° north of Mars on the 18th.

One of the most fascinating sights to observe is the Moon occulting, or passing in front of, a bright star. We have a chance to witness such an event just after first quarter, on the 24th, when the dark limb of the Moon occults Antares, in Scorpius, at 10:55pm, about 25 minutes before moonset.

Another opportunity to view a lunar occultation of a star occurs on the morning of August 4, when the waning gibbous Moon passes in front of 4.2 magnitude Psi1 Aquarii. The bright limb of the Moon passes in front of the star at 1:11am, and it re-emerges from the dark limb 1 hour later. 

Mercury has an evening apparition in August, though it is not a very favorable one, with the fleeting innermost planet remaining low in the west after sunset. It reaches its greatest elongation, 27° east, on the 9th. Mercury becomes difficult to observe later in the month, as it sets shortly after sunset.

We’ve seen the end of the Evening Star for this year, as Venus reaches inferior conjunction on the 13th. It begins setting before the Sun on the 5th.

Through the second half of August, Venus quickly re-emerges as the Morning Star, rising at least an hour before sunrise beginning on the 24th. Venus remains close to Earth all month, at under 0.33 AU, and will reveal a large and thin crescent phase with even a small telescope, presuming you have a clear horizon to view it.

Mars continues to hang low in the western sky for a short time after sunset. The Red Planet, which has been in Leo since June 20, moves into Virgo on August 17, and is joined by the 2.2-day waxing crescent Moon the following night. By the end of the month, it sets less than one hour after sunset.

Jupiter is now an evening planet, rising just before midnight in early August, and reaches western quadrature on the 6th.

Saturn reaches opposition in Aquarius on August 27. At 8.76 AU from Earth, the ringed planet is as close and bright as it will appear all year. 

Saturn’s ring plane angle (and also the orbital planes of its major moons) is more narrow to our perspective than it has been in over a decade. This makes detail in Saturn’s rings more difficult to observe, but with a larger-aperture telescope, you may begin to see its moons undergoing transits, occultations, and eclipses.

In early August, Saturn lies at nearly the same right ascension as NGC 7293 (Caldwell 63), the Helix Nebula, a large, but dim, planetary nebula in Aquarius. This makes the elusive nebula relatively easy to find using a telescope on an equatorial mount. On a moonless night, after aiming at Saturn, move the telescope 10° to the south. 

Another interesting note with respect to Saturn’s position: On August 5, the ringed planet will be in conjunction with Gonggong, a dwarf planet barely the size of Saturn’s moon Dione, that lies over 88 AU away from Earth, nearly ten times the distance to Saturn.

Saturn is joined by the full Blue Moon on the 30th.

Uranus is just a few degrees east of Jupiter, in Aries. At magnitude 5.8, it can be found with binoculars just a short distance from the Pleiades.

About halfway between Jupiter and the Pleiades, look for a quadrilateral of 4th and 5th magnitude stars resembling a radio telescope, with the open end of the dish pointed south. The stars are Botein (delta Arietis), zeta, tau1 and tau2 Arietis. Uranus (magnitude 5.8) forms an equilateral triangle with the southern two stars (the wide end of the radio dish).

Uranus is stationary and begins its retrograde motion on the 28th.

Distant Neptune, a blue speck shining at magnitude 7.7, is in Pisces, and rises just before 10:00pm in early August. It can be found 1° east of 20 Piscium, a magnitude 5.5 star located 5° south of the Circlet asterism. On the 5th, the waning gibbous Moon is 3° east of Neptune on the 4th.

Pluto, in Sagittarius, is well-placed for viewing in late evening. At a distance of nearly 34 AU and magnitude 14.4, it is best viewed during mid-month, when bright moonlight is out of view. It can be found 1.4° south-southwest of the globular cluster M75.

Asteroid 4 Vesta continues to move eastward through Taurus in August. It begins the month just over 3 AU away. At the end of August, it will be about 2.7 AU distant, moving to within 2.4° south of Tianguan (Zeta Tauri). At magnitude 8.2, it can be seen with binoculars on a dark night.

Ceres is now in central Virgo. At a distance of about 3 AU, it shines at magnitude 8.8, and is getting more difficult to observe as it gets lower in the sky. At mid-month, Ceres sets around 10:00pm.

The Perseid meteor shower peaks on August 12-13, but the shower remains active through much of August. The meteors originate from northern Perseus, which, although is circumpolar, the best chances of seeing meteors occurs after midnight, when the radiant point is higher in the sky. The meteors are dust grains left behind by periodic comet 109P/Swift–Tuttle. This year’s peak activity coincides with a favorable waning crescent Moon.