Abstract

The Netherlands have a long tradition in sky optical phenomena observing. Since 1890 for more than 75 years all observations have been collected, processed and brought together by the Royal Netherlands Meteorological Institute in the famous annual series 'Onweders, Optische Verschijnselen enz. in Nederland naar vrijwillige waarnemingen' ('Thunderstorms, sky optical phenomena etc in The Netherlands from voluntary observations'). The observations were gathered by volunteer observers with pleasure in seeing and studying sky phenomena. They were accepted and stimulated by the annual publication of their observations by the Meteorological Institute. The observers described their findings on special printed postal cards. In that way a network was active for decades by which efforts lots of material has been collected. Dutch observations from this period are referred to in several important publications in the first half of the 20th century.

© 1997 Optical Society of America