The Moon
The Moon is a 22-day-old waning crescent, and recently passed last quarter. From Cambridge, it is visible in the morning sky, becoming accessible around 00:41, when it rises to an altitude of 13° above your south-eastern horizon. It will then reach its highest point in the sky at 05:40, 39° above your southern horizon. It will be lost to dawn twilight around 06:52, 38° above your southern horizon.
| 17 Jan 2020 | – Moon at Last Quarter |
| 23 Jan 2020 | – The Moon at perihelion |
| 24 Jan 2020 | – New Moon |
| 29 Jan 2020 | – The Moon at apogee |
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.