Gibbous Moon

May 01, 2020

When the moon is out, it’s hard to see dimmer stars and deep sky objects. But there’s still plenty to appreciate about our natural satellite.

For one thing, it’s the easiest object to observe. Even a cheap pair of binoculars or a toy telescope will give you a good look at the moon’s details. And since there’s still a terminator, or shadow, crossing the moon; you can see something different every night. The terminator can accentuate textured features like craters and mountains, whereas the more sunlit areas of the moon can get washed out, making those details harder to see.

On Friday night (May 1, 2020), the terminator reveals one of the moon’s largest craters--Clavius (CLAY-vee-us). Named for the 16th-century German astronomer Christopher Clavius, who modified the original Gregorian Calendar. A change that is still considered accurate and in-use today. You’ll find it near the moon’s south pole. Friday night is also a good night for the Copernicus crater, which sits all alone at the edge of the Ocean of Storms. Look for it near the center of your view, right on the shadow.

Saturday night (May 2, 2020), the terminator reaches the edge of the large Sea of Rains in the northern Hemisphere, which is bordered by high mountain ranges and features the large Plato crater at its northern edge.

On Sunday night (May 3, 2020), the terminator falls on the small, but deep crater named Kepler near the equator, and the large Gassendi (GAS-end-ee) crater to the south, named for the 17th century French astronomer Pierre Gassendi, who estimated the moon’s diameter, and was the first known person to observe the transit of a planet across the sun.

So take a moment to appreciate our moon this weekend, and all the astronomers who helped us understand it.