August 2023 Observing notes from Robert Victor!!

Thank you to Bob Victor for the amazing write up on these Astronomical Treats this month and beyond!!!

The cornucopia of astronomical treats this month includes two "Super" Moons, one "Blue"; evening twilight moonrises Aug. 1-3 and Aug. 30-Sept. 2; spectacular views of the Milky Way during Moon's absence in the first hour after nightfall Aug. 6-19; the Moon uncovering Antares Aug. 24; and Saturn rising in early evening. Late-night and early morning morsels include prime moonless views of the Perseid meteor shower; a star masquerading as a satellite of Jupiter; a rich, star-filled eastern predawn sky; and a supersized Venus crescent rocketing up from the horizon day-by-day in late August.

August 2023 Evening Sky

At the start of August, Venus sets very soon after sunset, too early to appear on our evening mid-twilight map. By late in August, Saturn becomes visible in the evening twilight, low in ESE, joining half a dozen bright stars already present and well seen: The Summer Triangle of Vega, Altair, and Deneb high in eastern sky; Arcturus, the "Bear-watcher" star, high in west-southwest, with Virgo's Spica 33° to its lower left; and Antares, heart of the Scorpion, crossing through south to south-southwest. Left of the Scorpion is the Teapot asterism within Sagittarius, the Archer. The Milky Way star clouds look like steam issuing forth from the Teapot's spout, whose top two stars mark the arrow aimed just below the Scorpion's heart. Faint Mars and fading Mercury, low in bright twilight in the west, will be a serious challenge, requiring binoculars. Saturn reaches opposition on the night of Aug. 26-27, as Earth passes between the Sun and Saturn. The ringed planet is then visible all night; find it low in ESE at dusk, high in south in middle of night, and low in WSW at dawn. A telescope reveals the rings tipped 9° from edgewise, closer to edge-on than at Saturn's oppositions in recent years. On August 1, Saturn is 6.4° WSW of 3.8-mag. Lambda Aquarius and retrograding. At the end of evening twilight on Aug. 31, Saturn is 8.5° WSW Lambda Aqr, 4.4° ENE of Iota Aqr, and 9.6° ENE of 2.9-mag. Delta Cap. August 2023 Morning Sky

As the month begins, the Summer Triangle is sinking in the west to northwest morning twilight. Jupiter, high in southeast, remains the brightest morning "star", but it soon gets competition. During the second week, the "Dog Star" Sirius begins to appear above the east-southeast horizon, below and in line with the Belt of Orion, which is midway between Rigel and Betelgeuse, but not plotted on the chart. Sirius is the brightest nighttime star, but falls short of Jupiter's current brilliance by a full magnitude. Sirius, Procyon, and Betelgeuse form the Winter Triangle. If you can spot Sirius while it is still low in the sky, turn around and catch Altair about to set just north of west. Altair is the southernmost star of the Summer Triangle, which also includes Vega and Deneb in the northwest. If you can spot Sirius before Altair sets, then you can see both the Summer and the Winter Triangle simultaneously! Look 1½ to 2 hours before sunrise, in the darkness before dawn, and you'll be struck by the number and beauty of bright stars visible in the eastern sky. Extend Orion's belt away from Sirius, upward past Aldebaran and the Hyades star cluster, forming the V-shaped head of Taurus, the Bull, and onward to the compact Pleiades or Seven Sisters star cluster. These are wonderful subjects for binocular viewing! Look also for the Great Nebula in the Sword of Orion. Halfway between Orion's belt and the North Star is Capella, the "Mother Goat" star, rising high in the northeast. Below Capella and rising higher to the left of Orion in August's morning skies are Pollux and Castor, the "Twin" stars of Gemini, just 4½° apart. It's an excellent year for the Perseid meteor shower. Peak activity is expected in the predawn darkness hours of August 13. Meteors can light up anywhere in the sky, but what all members of this shower have in common, is that their tracks, extended backward, will radiate from a point in the constellation Perseus, below the "W" of Cassiopeia in the northeast. The Moon will be just a thin crescent, rising less than three hours before sunrise, so will not interfere with viewing. Distant Uranus and Neptune are easy to locate in the late night to predawn skies this month. Uranus, near mag. 5.7, is easily picked up with binoculars 2.7° to 2.9° SE of 4.3-mag. Delta in Aries -- see Chart 4 of Sky & Telescope's Pocket Sky Atlas -- and will commence retrograde on Aug. 31. Neptune, of mag. 7.8 and so more of a challenge, is already in retrograde, conveniently very close to the 5.5-mag. star 20 in Pisces. Through binoculars, look southeast of the Circlet of Pisces and northwest of Iota Ceti for a compact, six-star asterism we're calling Neptune's Dipper. It consists of the stars 20, 24, 27, 29, 33, and 30 Piscium, ranging in magnitude from 4.4 to 5.9. See Charts 76 and 7 of the Pocket Sky Atlas for the locations of these stars in relation to their surroundings. The end of the handle is marked by the 5.5-mag. star 20 Psc, the asterism's northwesternmost star. The handle, 20 through 24 to 27 Psc, is 2.8° long. The nearly rectangular bowl is almost 3° by 1° in size, with its long diagonal 29 to 30 Psc just 3.0° long. The entire figure fits into a field 5¼° wide, from 20 Psc to 33 Psc. In August, Neptune is retrograding, from 1.0° to 0.3° ENE of 20 Psc. On the night of Sept. 11-12, one week before opposition, Neptune will pass just 3.7' (arcminutes) north-northwest of 20 Psc, Look near Jupiter for 5.5-mag. Sigma in Aries at start of morning twilight. Note also 5.8-mag. Omicron Ari 1.7° W of Sigma. The 5.3-mag. star Pi Ari forms an isosceles triangle with Sigma and Omicron, to their north and 2.4° from each. This triangle will help the viewer notice small changes in the position of Jupiter. On Aug. 1, Jupiter is 1.5° WSW of Sigma Ari. By Aug. 7, Jupiter closes the distance to 1.0°. On Aug. 8, Jupiter is equidistant from both Omicron and Sigma Ari, 0.9° from each. On Aug. 13, Jupiter is 0.5° WSW of Sigma Ari. On Aug. 21, Jupiter is 1.3' (arcminutes) from Sigma Ari at start of a.m. twilight, and still just 1.1' from Sigma Ari one hour after Jupiter rises in late evening on Aug. 21. On Aug. 22 Jupiter is 1.6' from Sigma at start of a.m. twilight. So, minimum observable distance Jupiter to Sigma Ari is 1.1' for Palm Springs, shortly after Jupiter rises in late evening of Aug 21. (Actual minimum distance of 28" [arcseconds!] south of Jupiter's center occurs on Aug. 21 near 3 p.m. PDT, in daytime and several hours before Jupiter rises in N America. Jupiter's radius is then about 21", so the star misses Jupiter's S limb by only 7".) Is that an extra Galilean moon of Jupiter? For several mornings, August 18-26, Jupiter may seem to have a fifth Galilean moon, actually the 5.5-mag. star Sigma Ari, as follows, at the start of morning astronomical twilight, from Palm Springs: Aug 18, Sigma Ari 10.3' E of Jupiter; Aug 19, Sigma Ari 7.1' E of Jupiter; Aug 20, Sigma Ari 4.0' E of Jupiter; Aug 21, Sigma Ari 1.3' E of Jupiter; Aug 22, Sigma Ari 1.6' W of Jupiter; Aug 23, Sigma Ari 4.0' W of Jupiter; Aug 24, Sigma Ari 6.3' W of Jupiter; Aug 25, Sigma Ari 8.4' W of Jupiter; Aug 26, Sigma Ari 10.2' W of Jupiter; Aug 27, Sigma Ari 11.9' W of Jupiter. On Sept. 2 at start of morning twilight, Sigma Ari is 18.0' (0.3°) W of Jupiter. On Sept. 4, as Jupiter begins retrograde, Sigma Ari is 18.5' W of Jupiter. Then the distance will decrease. Retrograding, Jupiter makes another pass by Sigma Ari Sept. 13-21, but this time nearly 5' south of the star, on Sept. 17. That's far enough off the line of Galilean satellites that it shouldn't be mistaken for one of them. Jupiter will end retrograde on Dec. 30, 9.7° WSW of 5.5-mag. Sigma Ari. Getting back to morning sky at mid-twilight, closer to sunrise, Venus first appears above the horizon, just north of east, by around August 22. Venus then outshines Jupiter by nearly two magnitudes, but for its first several days, the twilight glow will make Venus seem less bright than it is. Once Venus becomes visible, you can see the morning lineup of three bright planets: Venus, low, north of east; Jupiter, high in south; and Saturn, low in west-southwest. Can you spot Fomalhaut, Mouth of the Southern Fish, before it sets, to the lower left of Saturn? Keep track of Venus daily as sunrise approaches. Telescopes, and even a pair of binoculars, will reveal Venus' crescent phase, changing from 4 percent illuminated and 16° upper right of rising Sun on Aug. 22, to 11 percent and 26° upper right of Sun on the 31st. This month, the Moon is full twice, on August 1st, and again on the 30th. . Both Full Moons occur near the Moon's perigee, when it's closest to Earth, so expect much trumpeting in the media about "Supermoons". Further, the second Full Moon in the same calendar month is sometimes (incorrectly) called a "Blue Moon." We'll have a genuine Blue Moon as originally defined -- the third Full Moon of an astronomical season with four -- on August 19, 2024. Since the Full Moon is at opposition to the Sun, rising around sunset and setting around sunrise, watch for Saturn near the Moon, from nightfall on August 2 until dawn on Aug. 3, and again during all the darkness hours on the nights of Aug. 29 and 30. Here is a listing of the Moon's encounters with other naked-eye planets and prominent stars. Predawn: Tues. Aug. 8, Last Quarter (half full), near Jupiter.

Wed. Aug. 9, fat crescent, near the Pleiades (Seven Sisters) star cluster.

Thurs. Aug. 10, waning crescent near Aldebaran and the Hyades cluster.

Sun. Aug. 13, thin crescent to the right of Pollux and Castor, the Twins; below them the next morning.

Tues. Aug. 15, very challenging 1-percent old crescent Moon, 2°-3° up in ENE, 32 min. before sunrise; less than 10° from Sun.

In early dusk on Thurs. Aug. 17, using binoculars 40 minutes after sunset, try for the 3-percent young crescent Moon, 9° N of W and only 3°-4° up. Can you spot faint Mars, 11° to Moon's upper left? How about Mercury, 9° lower left of Moon, and 5.3° lower right of Mars? Fri. Aug. 18, 40 minutes after sunset, the 7-percent crescent should be easy for unaided eye in clear, unobstructed skies. Use optical aid for faint Mars, about 1° below, and fading Mercury 5.5° lower right of Mars. Sun. Aug. 20, one hour after sunset, the 19-percent Moon is easy, low in WSW, with Spica 5° to left. On the next evening, the 28-percent Moon will be 7°-8° to Spica's upper left. On Thurs. Aug. 24, the 57-percent gibbous Moon occults, or covers Antares. The event will occur in daylight or bright twilight from western U.S., so a telescope will be required. From Lansing, MI, the advancing dark edge of the Moon snuffs out Antares at 10:33 p.m. EDT, in a dark sky, so the leadup to the event and the occultation itself can be easily observed with a telescope, and perhaps with binoculars. The point of contact on the dark limb will be 56° from the southern cusp (point of the crescent), more than halfway from the cusp to the midpoint of the dark limb. This quantity is known as the cusp angle (CA). Antares will reappear just before 11:35 p.m., on the bright limb, 56° from the southern cusp. At that time, the Moon will be only 5° up in the southwest, so observing conditions will be difficult. For a map of the region of visibility of the occultation and predictions for other locations in the U.S. and Canada, visit the website of the International Occultation Timing Association, or go directly to http://lunar-occultations.com/iota/bstar/0824zc2366.htm Remember to convert the Universal times to your own time zone: Subtract 4 hours from UT to get EDT; subtract 7 hours from UT to get PDT. Robert C. Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still helps to produce an occasional issue. He enjoys being outdoors sharing the beauty of the night sky and other wonders of nature. Robert D. Miller, who provided the evening and morning twilight charts, did graduate work in Planetarium Science, and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy. Dr. Jeffrey L. Hunt. who provided the graphs of planet rising and setting times for 2023, and for the Venus morning apparition getting underway in August 2023, is a retired planetarium director now living in the Chicago area. He has taught astronomy and sky watching to people of all ages. He studied astronomy education at Abrams Planetarium at Michigan State University. Jeffrey writes an astronomy blog at jeffreylhunt.wordpress.com and can be followed on Twitter at @jeff_hunt.