We got this question:
Which phase of the moon would be best for stargazing, and why?
And the answer is … it depends on what you want to do. Some people enjoy watching the moon itself, as it waxes and wanes in our sky. Some enjoy the fact that the moon appears near bright stars and planets at certain times of the month. For instance, the first quarter moon will pair up with the bright star Regulus tomorrow night, on May 21.
People also use the moon as a signpost. For instance the lit side of tonight’s rather wide waxing crescent moon points westward, and the dark or nighttime side points eastward. This evening, as darkness falls, the lit side of the moon points toward the brilliant planet Venus, which lurks close to the western horizon at nightfall. On the other hand, the moon’s nighttime side points in the direction of Regulus, the brightest star in the constellation Leo the Lion.
Some professional astronomers don’t care about observing the moon itself. They are more interested in observing objects in space much farther away than Earth’s moon. They look forward to moon-free nights, which let them look at deep-sky objects, such as galaxies, star clusters and nebulae. They like the moon at or near new phase! It’s best to look at these faint fuzzies in a night sky with little or no light.
Amateur astronomers using telescopes may also try to avoid the moon, because its glare interferes with the telescopic views of deep-sky objects. Especially around full moon, the moon casts a lot of light, washing out many nighttime treasures. At new moon, the moon is up during the day, not the nighttime. Around then, you won’t see the moon at all – unless you’re on just the right spot on Earth to watch one of the upcoming partial solar eclipses on July 13 and August 11, 2018.
In the meantime, what do we have to look forward to later this month? Watch for the moon to swing to the north of Regulus on May 21, north of the star Spica on May 25, and north of the planet Jupiter around May 27.
Bottom line: The best phase of the moon for stargazing depends on what you want to do. Some enjoy watching the moon itself. On the other hand, people using telescopes avoid the moon because its glare interferes with deep-sky objects.