Blue Moon Over Vecses, Hungary
June 28, 2007
The photo above shows a captivating blue Moon as viewed from Vecses, Hungary. On May 21, Saharan dust was blown north over central Europe. During the day, the micron-sized dust particles in the upper atmosphere caused Bishop's ring to appear around the Sun - a huge (about 28°) aureole coloured bluish-white inside and ochre outside. That night, the dust produced a spectacularly blue Moon -- a particularly rare sight. Particles having radii of approximately 600 nanometers scatter longer wavelengths (red light) more effectively than the shorter wavelengths (blue light). As a result, when particles of this size are found in the atmosphere, the disk of the Moon or Sun will have a decidedly bluish hue.