Monday, May 01, 2017

"Good Night, Moon"

The waxing crescent

5.3 days old

28.2 percent lit

April 28, 2017
By Alan McRobert 

Sunday, April 30 (click here)
• These spring evenings, the long, dim sea serpent Hydra snakes far across the southern sky. Find his head, a rather dim asterism about the width of your thumb at arm's length, in the southwest. (It's lower right of Regulus by about two fists at arm's length.) His tail reaches all the way to Libra rising in the southeast. Hydra's star pattern, from forehead to tail-tip, is 95° long.
• As twilight fades, look above the crescent Moon in the west for Pollux and Castor, and a similar distance left of the Moon for Procyon.
Monday, May 1
• At nightfall, the first-quarter Moon forms part of a gigantic curving arc: To the Moon's lower left is Procyon, to its upper right are Pollux and Castor, and continuing way farther right, you can include Menkalinan and then brilliant Capella. These stars alone, minus the Moon, form the Arch of Spring.
Tuesday, May 2
• It's May now. But wintry Sirius still twinkles very low in the west-southwest in twilight, far below Procyon. It sets soon after dusk. How much longer into the spring can you keep Sirius in view each evening? In other words, what will be its date of "heliacal setting" as seen by you?
Wednesday, May 3
• The waxing gibbous Moon, 1.3 light-seconds away, shines near Regulus, 79 light-years away. Regulus is the bottom star of the Sickle of Leo, marking Leo's forefoot.
Thursday, May 4
• The moon now shines under the belly of Leo — with Regulus to its right, Algieba a little farther to its upper right, and Denebola a lot farther to the Moon’s upper left.
Friday, May 5
• Now the Moon is under Leo's tail star, Denebola (by about a fist at arm's length). To the Moon's lower left is bright Jupiter, with Spica about half again farther on.
Saturday, May 6
• The Moon tonight forms a gently curving arc with, to its lower left, bright Jupiter and then Spica. Look between the Moon and Jupiter for 3rd-magnitude Porrima (Gamma Virginis), a fine, close telescopic double star.
• Summer is more than six weeks away, but the Summer Triangle is beginning to make its appearance in the east, one star after another. The first up in view is Vega. It's already visible low in the northeast as twilight fades.
Next up is Deneb, lower left of Vega by two or three fists at arm's length. Deneb rises about an hour after Vega does, depending on your latitude.
The third to rise is Altair, which shows up far to their lower right around midnight.