![]() ![]() He added a notional eclipse-forming layer of 75km height onto the Earth in his predictions. ![]() French astronomer André-Louis Danjon developed another method in mid-20th century. His method is still being used by the United States Naval Observatory to date. In 19th century, William Chauvenet, astronomer of the United States Navy, chose to enlarge the Earth's shadow by 2% for all his lunar eclipse predictions. Furthermore, the enlargement factor varies for every lunar eclipses. Back in the 18th century, astronomers realised that the Earth's shadow had to be enlarged by around 1.5% to 2.5% in order to match the actual observed time of the lunar eclipses. However, as the edge of the Earth's shadow is blurry, it is very difficult to predict and verify the start time and end time of a lunar eclipse. Lunar eclipse occurs when the Moon contacts the Earth's shadow. Such change is not observable in other star-related lunar occultation events.ĭuration of lunar occultation of Uranus: about 49 minutes If a telescope with low magnification is used, Uranus will appear almost as same as an ordinary star, but observers can see the change in brightness of Uranus within a few seconds during the beginning and the end of occultation. The entire occultation event will last for about 49 minutes. When occultation starts, it will take about 9 seconds for Uranus to disappear completely against the limb of the Moon when occultation ends, it will take roughly the same time for Uranus to reappear completely against the other limb of the Moon. Using a telescope with high magnification, Uranus will appear as a tiny blue disc where its edge will look relatively darker. At that time, the observation of Uranus becomes much easier.Īt this time when the lunar occultation of Uranus occurs, the angular diameter of Uranus is about 3.7 arcseconds, which is about 1/500 of that of the Moon. Yet, when a total lunar eclipse occurs, the brightness of the Moon drops significantly. However, when the Moon is near Uranus, even with a telescope, the bright moonlight will make the faint and tiny Uranus hardly observable. Telescope is almost indispensable in order to observe it. In comparison, the brightness of Uranus is much lower, which is near the limit of human eye. From many lunar occultation events, the lunar occultation of Venus draws most attention as these two objects are very easy to be observed since they are both very bright in the sky. When the Moon is close enough to a planet so that it blocks the light from the planet, a lunar occultation event occurs. The size of Uranus is not drawn to scale in the above diagram.Īs the Moon orbits the Earth, the position of the Moon on the celestial sphere shifts from West to East gradually (therefore the rising time of the Moon always delay day by day), and since the orbital plane of the Moon is very close to the orbital plane of the planets, the Moon will sometimes get close to the planets visually. In this image, the Moon is fixed in order to show the relative motion of the Uranus. In fact, the position change of Uranus is mainly due to the motion of the Moon. The occultation starts at the East side of the Moon and ends near the South side of the Moon. The position of Uranus during the lunar occultation. During this total eclipse, the Moon will pass in front of Uranus, resulting in an occultation event of the planet. Only in a total lunar eclipse when the brightness of the Moon drops significantly, we can see the Moon and Uranus side by side in a telescope. Since the planet Uranus is a lot dimmer than the Moon, under most circumstances even if they are close together, the former is often hidden in the latter's glare. Interestingly, the lunar eclipse of 8 November will be accompanied by another astronomical event, the lunar occultation of Uranus. The next total lunar eclipse visible in Hong Kong will occur on 8 September 2025. The subsequent partial phase will end at 8:49 pm. At 6:16 pm, the total phase begins with the Moon entering the Earth's umbra completely and will last about 1 hour and 26 minutes. The eclipse has already begun when the Moon rises at 5:37 pm that evening. A total lunar eclipse, during which the Moon would take an uncommon coppery-red hue, will be visible across the territory in Hong Kong on 8 November 2022. ![]()
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