INFLUENCE OF A SOLAR ECLIPSE ON TWILIGHT

The morning twilight of the presunrise sky was measured at the Hoher-L ist Observatory during the total eclipse of 22 July 1990. The location of observation was far away from the central eclipse zone. The lumina nce showed a deep minimum in twilight during the main phase of the sol ar eclipse compared with normal conditions. A first order scattering m odel explains the observations reasonably well and shows that the sky radiation during the first phase of twilight at a location far away fr om the central umbra depends primarily on the height profile of the ai r pressure between approximately 100 and 200 km.