Young, Charles A. (Charles Augustus), 1834-1908, Young, Anne Sewell, b. 1871., ed · Boston, New York [etc.] Ginn and Company · leaf 139
laid with filmyclouds, which usually require a good telescope and helioscopeto make them visible, but sometimes, though rather infre- §185] SUN SPOTS. 125 quently, are conspicuous, — as in the figure. Usually, also,within the umbra there are a number of round and very blackspots, sometimes called… … Fig. 48. — A Normal Sun Spot. (Secchi; modified.) nucleus gives about one per cent as much light as a correspond-ing area of the photosphere: the blackest portion of a sun spotis really more brilliant than a calcium light. Very few spots are strictly normal. They are often gathered ingroups with a…
Astronomy · Constellations
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