September 12, 2018: Venus, Jupiter and the crescent Moon.
The sky is very clear this evening. The crescent moon, overexposed in the image, shows Earthshine. Sunlight reflected from Earth falls on the night portion of the moon and gently illuminates it. Brilliant Venus is just above the southwest horizon. In about 10 days, Venus begins its cycle of greatest brightness. Jupiter appears over 17 degrees to the upper left of Venus. Jupiter gets closer to Venus during the month, but there is no conjunction.
September 8: Before sunrise, locate the thin waning crescent moon (28.0 d, 2%) 1.8° to the upper left of Regulus with Mercury 4.4° below the star. Mercury (m = −1.2) is only 4.5° up in the east-northeast 30 minutes before sunrise. You’ll need a clear horizon and binoculars to see the trio in bright twilight.
September 6: In the predawn eastern sky, the waning crescent moon (26.0 d, 15%) is on a virtual line that connects the Gemini Twins, Castor (α Gem, m = 1.6) and Pollux (β Gem, m = 1.2). The moon is 9.2° from Pollux. Thirty minutes before sunrise, with binoculars, look in the east-northeast for Mercury (m = −1.1) 1.2° to the left of Regulus. Mercury is 6.5° up in the sky.
In the evening sky, Saturn’s retrograde ends. It is 5° to the upper right of Kaus Borealis (λ Sag, m = 2.8), the star at the top of the lid of the Teapot of Sagittarius, and 45° from Jupiter. Mars and Jupiter have the same visual brightness (m = −1.9). Because they have distinctly different colors, do they appear to be the same brightness to you? While they are over 70° apart, it is not appropriate in formal astronomy to compare respective objects’ brightness, but it is a fun activity. Look near the end of twilight because they have nearly the same altitude early in the evening.
September 3: During predawn hours, the thick waning crescent moon (23.0 d, 46%) is 5.2° to the lower left of Aldebaran.
The North America Nebula
Credit & Copyright: Jason Ware
September 4: As the moon approaches its new phase, look for the Milky Way arching across the evening sky. Cygnus, with its bright star Deneb (α Cyg, m = 1.2), appears to be flying southward along the soft glow of our galaxy. It ranks near the bottom of the 20 (visually) brightest stars list. Along with Rigel (β Ori, m = 0.2), Deneb is one of the brightest stars in our sky. Both stars are approximately 100,000 times brighter than our sun. Deneb seems dimmer to us because it is likely twice the distance of Rigel, and it is surrounded by fewer bright stars. It seems less notable than those stars that gleam from the Orion region of the sky. The Cygnus neighborhood is crowded with dim features. Walter Scott Houston, the expert chronicler of deep sky observing, noted this in his columns in Sky & Telescope magazine. Houston explained that certain sections of the sky had many objects that were not identified on charts, especially those in the densely packed Milky Way. His articles were compiled into a book, Deep-Sky Wonders, by Stephen James O’Meara. In the chapter for September, Houston provided accounts of viewing the North American Nebula. Houston’s description: “One of the most controversial objects among amateur astronomers, the North American Nebula, is familiar from photographs as a large diffuse glow about 3° east and 1° south of Deneb. There has been remarkable diversity of opinion on how small a telescope can show this object visually” (p. 202). While I have never seen it naked eye, Houston stated that some observers reported seeing it without optical assistance. (If you’ve seen the nebula without a telescope or binoculars, describe your observations for me. Enter your description on this document: https://tinyurl.com/north-american-nebula.)
