Look west on April 19, about 30 to 90 minutes after sunset, and a thin crescent moon will hang above Venus and the Pleiades in a brief evening display. The waxing crescent will be 11% lit and sit about 20 degrees above the western horizon, offering one of the clearest naked-eye skywatching sights of the month.
The timing follows the new moon on April 17, when the lunar disk turned dark from Earth’s perspective. By Saturday night, the moon will have moved into position above the Pleiades, the star cluster better known as the Seven Sisters, a collection of more than 1,000 blue-white stellar bodies.
Venus will appear below the moon and set about two hours after the sun, making it the brightest marker in the scene. Uranus will also lurk about 5 degrees to Venus’s upper right at magnitude +5.8, but it will be difficult to pick out with the naked eye. For most viewers, the main show will be the moon, Venus and the star cluster arrayed in a tight patch of western sky just after dusk.
The moon may also show earthshine, the faint glow caused by sunlight bouncing off Earth’s cloudy surface and lighting the lunar side that would otherwise stay in shadow. Astronomers also call it the Da Vinci Glow or the old moon in the new moon’s arms, and it is easiest to see on nights around the new moon phase. That makes this weekend’s scene more than a simple crescent sighting: it is a rare chance to see the dark side of the moon outlined by light reflected from Earth itself.
The window will be short, and that is the point. Anyone hoping to catch moon tonight should look soon after sunset, because the alignment will be fleeting and Venus will sink lower as twilight deepens.