Moon, Venus and Crespuscular Rays

January 20, 2017


CrescentMoonVenus_Conjunction_DSC00775 (5)

Photographer: Patti Weeks
Summary Author: Patti Weeks

Shown above is the three-day-old, waxing crescent Moon as seen from eastern North Carolina, near Greenville, in the southwestern sky, at twilight, on December 2, 2016. It's in virtual horizontal alignment with the brilliant planet Venus, to its left. As twilight deepened, pinkish-orange crepuscular rays began to materialize. These twilight rays result from obstructions, such as mountains or clouds (the latter in this case) and are made visible by haze or dust in the atmosphere. Due to the illusion of perspective, the rays appear to diverge in a fan-like manner from the horizon, but they're actually parallel.

The following night, December 3, the waxing crescent Moon appeared higher in the sky and was directly above Venus. This Moon-Venus conjunction is seen in the bottom photo, taken through boat masts decorated with holiday lights. Two or more astronomical objects appearing to be close together is another optical illusion, for being in conjunction simply means that the objects are on the same ecliptic longitude. Note the corona about this young crescent.

Photo Details: Top - Camera Maker: SONY; Camera Model: DSC-HX400V; Lens: Sony 24-210mm F2.8-6.3; Focal Length: 5.97mm; Aperture: ƒ/3.2; Exposure Time: 0.020 s (1/50); ISO equiv: 100. Bottom - same except: Focal Length: 19.22mm; Aperture: ƒ/4.0; Exposure Time: 0.250 s (1/4); ISO equiv: 1600.