Skywatch Line for Monday and Tuesday, July 24th and 25th, 2023

This is Dudley Observatory’s Skywatch Line for Monday and Tuesday, July 24th and 25th written by Joe Slomka.

The Sun sets at 8:25 PM; night falls at 10:27. Dawn breaks at 3:38 AM and ends with the Sun rising at 5:40.

Monday’s Moon rises in southwestern Libra at 12:14 PM, is 25° high at 9 PM, appears 31 arc-minutes in size, appears 62% illuminated and sets at 11:39 PM. Tuesday’s Moon rises in Virgo at 1:20 PM, is officially “First Quarter” at 6:07 PM, 25° high in the southwest, 30 arc-minutes, 51% lit and sets at Wednesday’s midnight. Monday’s Moon is only 3° from the bright star Spica and Tuesday’s about 10° away.

Leo hosts all three evening planets: Mars, Mercury and Venus. Venus will be the brightest and easiest to find. It blazes with minus 4th magnitude, 48 arc-seconds, 11% lit, but only 2° high and sets at 9:13 PM. Mercury lies 6° above Venus, glimmers with zero magnitude, 71% lit, 5° high and sets at 9:27 PM. Mars is 11° furthest from Venus, 1st magnitude, only 4 arc-seconds, 11° high, 96% lit and sets at 10:02 PM. All are very close to the horizon and require a clear western horizon.

Comet C/2023 E1 continues circling around the Little Dipper, glowing with 14th magnitude, 70% lit and 49° highest at 12:50 AM.

The rest of the planets rise during night. Saturn appears in southwestern Aquarius at 10 PM, glimmers with zero magnitude, 18 arc-seconds, highest at 3:21 AM and 31° high at 5 AM. Neptune, situated 21° to Saturn’s South, in Pisces, rises at 10:45 PM, flickers with 7th magnitude, 2 arc-seconds, highest at 4:40 AM with 44°.

Jupiter and Uranus share Aries. Jupiter outshines Saturn, glimmering with minus 2nd magnitude, emerges with a large 39 arc-seconds, rises at 12:35 AM, 47° high in the Southeast. The Jovian moon Ganymede’s shadow begins to cross the planet’s face at 1:43 AM on Wednesday and exits at 3:40 AM. Uranus lurks 10° to Jupiter’s East, shines with 5th magnitude, 3 arc-seconds, rises at 12:58 AM and is 44° high.

Only two constellations refer to real people. Coma Berenices lies above Leo’s tail, and is now low in the West. The other constellation, Scutum, is visible in summer skies. Scutum is a dim constellation above teapot-shaped Sagittarius within the glorious Milky Way. It is the fifth smallest constellation.

The astronomer Johannes Hevelius (Jan Heweliusz) was at first a beer brewer, but later became interested in astronomy. He built an observatory in 1641; he preferred to use quadrants for observing, but also had a large telescope. The observatory was named for Polish King Jan Sobieski. The Ottoman Empire threatened to invade Europe. Sobieski commanded an allied army and stopped the enemy outside of Vienna. Hevelius created Scutum partially to commemorate this victory, but also to thank the king for rebuilding his Gdansk observatory. His Polish descendants, today continue to support amateur astronomers.