The September 28th total eclipse of the Moon

Armagh Observatory, 18 September 2015. Armagh Observatory reports that, if skies are clear on the night of 27/28 September, skywatchers will witness a rare total eclipse of the Moon during the early hours of Monday 28th. The penumbral phase of the eclipse begins soon after midnight on the 27th, at 01:11 (BST), followed by the main partial phase, which begins at 02:07. Totality starts at 03:11 and continues to 04:23, with maximum eclipse occurring at 03:47. The Moon then moves slowly out of the Earth’s shadow, the partial eclipse ending at 05:27 and the penumbral phase ending at 06:22.

This will be the first lunar eclipse visible from Northern Ireland for nearly five years, that is, since 21st December 2010, when the Moon was seen low down in the North-West around dawn and set whilst still eclipsed in the dawn mist. The next total lunar eclipse visible in its entirety from Northern Ireland will not occur until 21st January 2019. However, a slightly earlier eclipse on 27th July 2018 will see the Moon rising whilst still totally eclipsed, and so (as in 2010) its visibility will depend on having clear skies in the appropriate direction right down to the horizon.

A total lunar eclipse occurs when the Moon, in its elliptical orbit around the Earth, happens to pass exactly through the shadow of the Earth in space. When this happens the Earth blocks direct sunlight from reaching the Moon, and the otherwise Full Moon is significantly diminished in brightness. As the eclipse progresses from penumbral to partial phase, and then towards totality, it is interesting to observe how the dark shadow of the Earth slowly encroaches on the Full Moon until the Moon is nearly completely obscured.

Professor Mark Bailey, Director of the Observatory, said: "Every total lunar eclipse is different, and given the right weather conditions is well-worth observing. Each provides a different and unique visual experience. And even if it is cloudy, you can still admire how dark it becomes during the short period of totality before the Moon returns to full brightness. If it is clear, the changing visual appearance of the Moon during the different phases of the eclipse will provide stargazers with great photo-opportunities."

The reason that the Moon may not be totally obscured during a total lunar eclipse is because some sunlight passes through the edge of the Earth’s atmosphere as seen from the Moon, and is refracted onto the lunar disc. This helps to explain why the Moon often appears a copper, or dull red colour during a lunar eclipse, because the blue and yellow rays of the Sun are more easily scattered and absorbed by the Earth’s atmosphere. The colour and brightness of the Moon during a total lunar eclipse depends in part on how centrally it passes through the Earth’s shadow, but also on how transparent or cloudy are those parts of the Earth’s atmosphere that enable sunlight to reach the Moon. During a very dark eclipse the Moon may be almost invisible. Less dark eclipses may show the Moon as dark grey or brown; or as rust-coloured, brick-red, or (if very bright) copper-red or orange

The total eclipse was observed by skywatchers across Northern Ireland and by astronomers at Armagh Observatory.

This image shows the eclipse as seen at the Observatory by astronomers Ruxandra Toma and James Finnegan.

This image is a montage showing the evolution of the lunar eclipse at the Observatory by astronomers Ruxandra Toma and James Finnegan.

This image is an animated gif based upon a timelapse of the eclipse as seen at the Observatory by astronomers Ruxandra Toma and James Finnegan. The animated gif was created by Onur Satir.

For further information please contact: Mark Bailey at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; mebat signarm.ac.uk; URL: http://climate.arm.ac.uk

Last Revised: 2015 October 15th