2019 January 19

Early morning total eclipse of the Moon this Monday

John Mason

This coming Monday, in the early morning hours of January 21, there will be a total eclipse of the Moon. Full Moon itself occurs at 05:16 UT on January 21 with lunar perigee (its closest approach to the Earth) occurring just 14h 43m later at 19:59 UT. When a Full Moon occurs close to the Moon’s perigee, it is often dubbed a ‘Supermoon’. This is why some people are calling this is a ‘Supemoon eclipse’.

Eclipses of the Moon occur when the Full Moon passes through the cone of shadow cast by the Earth into space. Weather permitting this will be a fascinating event to watch from the British Isles because the eclipse will be visible in its entirety everywhere, giving plenty of opportunities for stunning pictures of a ‘ghostly red Moon’.

The lunar eclipse begins at 02:36 UT (in the early hours of Monday morning) when the Moon enters the fainter outer part of the Earth’s shadow known as the penumbra. At this time the Moon will be fairly high in the south-west, almost directly below, and in line with, the stars Castor and Pollux in Gemini, the Twins.

The main phase of the eclipse begins at 03:33 UT when the Moon first enters the central, dark part of the Earth’s shadow known as the umbra and the partial eclipse begins. The eclipse becomes total at 04:41 UT and lasts for a full 1 hour 2 minutes. Maximum eclipse is at 05:12 UT. At this time the Moon will be dropping down into the western sky, among the faint stars of Cancer, the Crab, but still high enough to be well clear of trees and buildings.

The total phase of the eclipse ends at 05:43 UT. As the Moon will be passing through the upper part of the Earth’s umbral shadow, it is probable that the northern parts of the eclipsed Moon may appear quite bright even during mid-totality, but one never quite knows how dark or how bright a lunar eclipse will be. Everything depends on the conditions in the Earth’s upper atmosphere through which all light falling onto the shadowed Moon has to pass. There have been lunar eclipses when the Moon has been difficult to find even with a telescope, while at other eclipses it has remained bright red or vividly coloured. The Moon appears a reddish hue because of Rayleigh scattering – the same effect that causes sunrises and sunsets to appear reddish – and the refraction of that light by the Earth’s atmosphere into its umbral shadow.

The partial eclipse ends at 06:50 UT, when the Moon exits the umbra. By this time the Moon will be getting quite low in the west-north-western sky. The faint penumbral phase finally ends at 07:48 UT.

And don’t forget that if you do get up before dawn to watch the lunar eclipse that Venus and Jupiter are still a spectacular sight together in the south-eastern twilight sky, with Venus much the brighter of the pair a few degrees above Jupiter.

Let’s hope for clear skies in the early morning hours of Monday, January 21!

Dr John Mason
Press and Publicity Officer & Meteor Section Direction

If you make any observations of the forth coming eclipse, please submit them to the BAA Lunar Section and upload them to your Member Page. To view other members’ observations of previous eclipses check out the gallery  and the eclipse  and lunar observations uploaded to the BAA Member Pages..

[Thumbnail image: John Bell, Total Lunar Eclipse, captured 27/09/2015]