The annular solar eclipse of 2021 June 10

The central line of the annular solar eclipse of 2021 June 10 begins at sunrise at 9:55 UT in Ontario, Canada at longitude 89°W, latitude 50°N and crosses northern Quebec, Baffin Island, the north-western tip of Greenland and the Arctic Ocean to end at sunset at 11:29 UT in far eastern Russia, at longitude 156°E, latitude 64°N.

The eclipse achieves its greatest duration of 3m 51s over extreme north-western Greenland at 10:42 UT in longitude 67°W, latitude 81°N, with the Sun at an altitude of 23° and the width of the path being 523 kilometres. Central eclipse at local apparent midnight, the Sun’s lower transit, takes place at 11:01 UT in long. 165°W, lat. 88°N. It is interesting to note that the annular phase is visible at the North Pole. Partial phases of the eclipse are visible from eastern North America, Arctic regions, most of Europe and much of Asia.

The eclipse is next in the series which includes that of 2003 May 31, which was annular in the north of Scotland, the Hebrides, Orkney and Shetland.

In the British Isles a partial eclipse is visible during the morning, its magnitude (the proportion of the Sun’s diameter which is obscured at greatest eclipse) ranging from 0.30 along the Kent coast to just over 0.50 in Shetland.

The extent of the penumbra over the British Isles is illustrated in Figure 1, from which it is possible to obtain the time and magnitude of greatest eclipse for any location. For instance, at Edinburgh maximum eclipse takes place at 10:18 UT with a magnitude of 0.43, while at Greenwich greatest phase occurs at 10:13 UT, the magnitude being 0.31.

Table 1 gives some local circumstances. P indicates the angle of the Moon’s centre measured from the north point of the solar disc through east, while V represents the corresponding angle reckoned anticlockwise from the vertex of the solar disc. Finally, Figure 2 illustrates the appearance of greatest eclipse for some places.

Peter Macdonald

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