Observing the First Quarter Moon

Posted by Kelly on August 28th, 2012

The Moon through a Telescope

First Quarter Moon

First quarter is a great time to observe the Moon. The Moon is available in the evening after the sky has completely darkened but you don’t have to stay up late to catch it. The terminator nicely divides the satellite, allowing for much of the surface to be seen and also putting the mountains and valleys into stark contrast. On a recent night with a first quarter Moon, I dragged my smaller 4.5-inch scope outside because the larger scope would be overkill (and is not easy to carry). I’ve observed the Moon plenty of times, but usually it was just as a stopping off point before and after targeting deep-sky objects. It is not usually my primary observing target and I haven’t really taken the time to sit down with a moon atlas and learn the names of everything I’m spying.


One of the most notable areas the eye gravitates to when observing a first quarter moon is the half circle of mountains in the northern hemisphere (which will look like it’s at the bottom of the moon through a telescope’s inverted view). The northern line of mountains is named Montes Alpes, the one on the side that leads away toward two larger craters is Montes Caucasus and the lower ridge is Montes Apenninus. These mountain ranges are all named after earthly features.


The highest mountain peak in Montes Alpes is named Mons Blanc and towers at 11,800 feet high. Montes Apenninus abuts a valley where the Apollo 15 crew landed and explored the moon. The three craters you can see inside Mare Imbrium (that’s the flooded plain that you can only partially see that sits inside the three mountain ranges) are, from largest to smallest, Archimedes, Aristillus, and Autolycus. These craters are all named after ancient Greek astronomers/scientists. Luna 2, which became the first spacecraft to reach the Moon’s surface in 1959, landed between Archimedes and Autolycus on a plain known as Sinus Lunicus.


Folklore has claimed to see many things in the Moon, from men to rabbits, but through my telescope during the first quarter Moon, I see a more modern icon waiting for observers. This is a great feature to point out to even the youngest kids at the eyepiece.


Tracing the terminator during first quarter Moon, you’ll come to a spot near the Moon’s equator that nearly resembles Mickey Mouse’s iconic silhouette. The likeness is more noticeable in the inverted telescope’s view because Mickey’s head is at the bottom and not the top of the trio. The crater that marks the head is named Ptolemaeus, and the ear that is attached to the head is a crater named Alphonsus. The ear that is floating just off Mickey’s head is the crater Albategnius.


With the vast array of craters pockmarking the Moon, maybe your younger observers can find their own Mickey Mouse head, or even a formation made entirely from their imagination.


Leave a Comment


Article Sections

Astronomy articles
Solar System Guide
Space Exploration
Cosmology articles
Book Reviews


Night Sky Guide
Buying a Telescope
Historical Eclipses
Meet Astronomers
The Constellations

Our Community

Read blog posts
Meet the Team