Green, blue and violet flashes

Green flashes are elusive phenomena during sunset and sunrise caused by the atmospheric refraction near the horizon. The shorter the wavelength, the larger the refraction, thus at sunset the refractive delay of the sunset is longer for shorter wavelengths: The green/blue sun sets later than the yellow sun. To observe these phenomena, a clear atmosphere is essential. The even rarer blue and violet flashes can be observed in particular from high altitudes, where the air is even clearer and less atmospheric reddening is affecting the observation. The pictures presented here have all been shot from an altitude of 2200 m a.s.l., and the sun sets in an "ocean of clouds" rather than on the horizon, i.e. also at high altitudes. Note that the violet flash observed on 14.01.2004 09:06 shows the rising sun over the island of Tenerife. The height of the valley through which the flash shines is approx. 2000 m a.s.l.

11.05.2004 21:55 25.08.2004 20:45 14.01.2004 09:06
28.04.2004 21:46 28.04.2004 21:46 28.04.2004 21:46
16.07.2003 22:15 04.05.2004 21:53 04.05.2004 21:53
04.09.2004 07:49 04.05.2004 21:52 02.05.2004 21:52
04.05.2004 21:53 04.05.2004 21:53 04.05.2004 21:53
All pictures have been taken during 2003-4 from the Roque de los Muchachos Observatory (2200 m a.s.l.), Canary Island of La Palma, at sunset or sunrise. Times are WET (=UTC) or WEST (=UTC+1). Equipment: Canon EOS 10D, 320mm/800mm effective focal length lens. No digital enhancements to the pictures shown here.

For explanations on the phenomenon of the green flash, see the introduction to Green Flashes by Andrew Young.

Even more stuff: Atmospheric optics, My Pictures Of the Day, Beautiful subsun and subparhelia,

All pictures © R. Wagner 2003-4