The Moon
The Moon is 7 days old, waxing gibbous, and recently passed first quarter. From Fairfield, it is visible in the evening sky, becoming accessible around 17:14 (EST) as the dusk sky fades, 56° above your southern horizon. It will then reach its highest point in the sky at 17:57, 57° above your southern horizon. It will continue to be observable until around 23:45, when it sinks below 7° above your western horizon.
| 13 Jan 2021 | – New Moon |
| 20 Jan 2021 | – Moon at First Quarter |
| 21 Jan 2021 | – The Moon at apogee |
| 28 Jan 2021 | – Full Moon |
The Moon at First Quarter. Simulated image courtesy of Tom Ruen.
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.