The Moon

by Dominic Ford, Editor

The Moon is 15 days old, waning gibbous, and recently passed full moon. From Ashburn, it is visible between 17:35 and 05:28. It will become accessible around 17:35, when it rises to an altitude of 9° above your eastern horizon. It will reach its highest point in the sky at 00:03, 71° above your southern horizon. It will become inaccessible around 05:28 when it sinks below 5° above your western horizon.

10 Dec 2019  –  The Moon at aphelion
12 Dec 2019  –  Full Moon
18 Dec 2019  –  The Moon at perigee
18 Dec 2019  –  Moon at Last Quarter
The Moon

The Moon at First Quarter

The Moon is the Earth's only natural satellite, orbiting it once every 27.3 days, at a distance of 380,000 km (0.00254 astronomical units).

It has almost exactly the same angular size as the Sun – roughly half a degree – a coincidence which means it can occasionally completely cover the Sun's disk to generate a total solar eclipse, but with so little margin that the geometry has to be absolutely exact.

The Moon is the only heavenly body on which surface features can be resolved by the unaided eye. Its mottled pattern of light and dark areas represent two distinct types of terrain. The dark areas are called maria – originally so named because they were thought to be oceans of water, but they are now known to be vast flat volcanic planes. Between the maria, the lighter colored terrain is considerably rougher and more mountainous – the lunar highlands.

To bring the Moon's heavily cratered surface into view, nothing more expensive than a cheap pair of binoculars is needed.




Color scheme