SIDIAILLES (18) 03.03.2013

On 3 March 2013 at about 23:00 near Sidiailles (18), a motorist saw something like a white cross among the stars, then, farther along, noticed a coloured light moving in the sky. He observed for 1.5 hours. Gendarmes called to the scene also saw and filmed the oscillations. The accounts and video describe a generally stationary point changing colour and oscillating slightly and randomly. Sirius, magnitude -1.44, was in the viewing direction at azimuth 225°, compared with about 212° measured by the gendarmes, and only 15° above the theoretical horizon. GEIPAN explains that the weather could favour extreme scintillation; see Météociel. Falling pressure continuing the next day indicated strong winds aloft, which cause strong scintillation. Low temperature could also create atmospheric optical effects, such as halos or crosses, if ice crystals were present. The source refers to information on stellar scintillation. An autokinetic illusion may also have contributed; see the corresponding reference. GEIPAN classifies the case A: observation of Sirius with strong scintillation due to particular weather conditions.