R e s e a r c h
During the seventies, six photographs of light pillars in high clouds found their way to the Dutch-language popular scientific literature . Four of these (one black & white photo and three high-quality colour slides) were taken by amateur astronomer Frans VAN LOO from his former home in Itegem, Belgium (see OP-PH-01 to -03 in our picture gallery dealing with artificial light pillars).
A typical light pillar display photographed by Frans VAN LOO from Itegem, Belgium. The reflections were caused by flaring activities in the Antwerp harbour. The photo was taken on October 25, 1976, at 18h35 UT. Stars are visible through gaps in the cloud deck. Yellow lines indicate azimuth and elevation for the centre of the main reflection. The distance between the spot from where the picture was taken and the location of the then largest standpipe at the petrochemical complex was 31.6 km or 19.6 miles.
Map of Flanders, Belgium, with location of the main standpipe at the FINA ANTWERP OLEFINS plant (formerly PETROCHIM). α defines the picture angle of the transparency taken by Frans VAN LOO on October 25, 1976. The yellow line indicates the azimuth for the flare.
The light source responsible for the bright pillar was a combustion flame emanating from a 204 m (669 feet) high standpipe at the former PETROCHIM plant, now operated by FINA ANTWERP OLEFINS, and located 31.6 km (19.6 miles) northwest of Itegem. Knowing the distance between the observer and the light source as well as the angular elevation of the streak, the altitude of the reflecting layer could be fixed at approximately (31.6/2 x tan17° =) 4.8 km or roughly 3 miles. Data gathered by a meteorological balloon launched from Uccle, Brussels, 5 ½ hours after the picture was taken, mention temperatures below -10° C at that altitude, a humidity exceeding 80% and winds blowing from the south at speeds of 60 km/h (37 miles/h). According to the official data gleaned from the archives of the Belgian Royal Institute for Meteorology, a low pressure area over Brittany, carried mild, sometimes unstable, maritime air over Belgium. The minimum air temperature that night was 8.2° C, the maximum temperature during the day was 12.4°C .
Notes & References
These six pictures were published in five different publications, namely: