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Partial Lunar Eclipse on 19 November 2021


A partial lunar eclipse will be visible in Hong Kong on November 19 (Friday). This is the second lunar eclipse this year, after the first one in May. Members of the public may enjoy this event during the evening when the Moon rises from the east-northeast horizon. At the time of moonrise at 5:38pm that day, the "maximum eclipse" stage has already ended. The Moon is leaving the umbra gradually and the partial eclipse ends at 6:47pm when the Moon exits the Earth's umbra completely. The whole eclipse ends when the Moon leaves the penumbra at 8:06pm.

During the partial lunar eclipse, the Moon will not be completely covered by the Earth's umbra. However, since the Moon is at a low altitude and the sky is not completely dark when the eclipse is in progress, it may take a bit longer to pin down the Moon. At 6:00pm that day, the Moon is still less than 5 degrees above the horizon, so special attention should be paid to the height of obstacles in the east-northeast direction when selecting a site for observation.

Details of the Lunar Eclipse


Type: Partial lunar eclipse
Magnitude: 0.97
Main Visible Area: America, Pacific Ocean, East Asia, Australia, Northern Europe

Moon enters penumbra, Not visible. Moon enters umbra, Not visible. Maximum eclipse, Not visible. Moonrise, 17:38. Moon exits umbra, 18:47. Moon exits penumbra, 20:06

Source: U.S.N.O.

This video simulates the telescopic and naked eye views of the partial lunar eclipse observed in Hong Kong.

Cause of Lunar Eclipse


When the Sun, the Earth and the Moon are aligned, the Moon will enter the Earth's shadow, resulting in a lunar eclipse. Depending on how the Moon comes in contact with the Earth's shadow, lunar eclipses can be divided into three types, namely the penumbral eclipse, partial eclipse and total eclipse. A penumbral lunar eclipse happens when the Moon enters the penumbra of the Earth; whereas a partial lunar eclipse happens when only part of the Moon enters the umbra. When the Earth's umbra covers the Moon completely, a total lunar eclipse results. A partial lunar eclipse can be divided into five stages: Moon enters penumbra, Moon enters umbra, Maximum eclipse, Moon exits umbra and Moon exits penumbra. Only the last two stages can be seen in Hong Kong during the partial lunar eclipse this time.

Titbits about lunar eclipse

1 hour before the partial eclipse 10 minutes before the partial eclipse
These two images were taken during the phase of the penumbral lunar eclipse before the partial lunar eclipse on 7 August, 2017. The image on the left was taken 1 hour before the partial eclipse. The image on the right was taken 10 minutes before the partial eclipse. The penumbral lunar eclipse is not obvious at its early stage. When the partial eclipse approaches, it can be seen easily that the surface of the Moon is dimmer.

moon during partial eclipse
Image of the Moon above shows the partial lunar eclipse during the lunar eclipse process on 26 May 2021.

Live Streaming of Partial Lunar Eclipse


The Hong Kong Space Museum will live stream the partial lunar eclipse via its YouTube channel. Curators will introduce the science behind lunar eclipse and share interesting tidbits related to this astronomical phenomenon.

Live Streaming of Partial Lunar Eclipse

Speaker: Assistant Curators of the Hong Kong Space Museum
Date: 19 November 2021 (Friday)
Time: 5:30 - 7:00pm
Language: Cantonese
Online Platform: YouTube (No registration required for the live streaming)