Helios Astronomy club was invited by one of it's members Lieven - thanks for the nice invitation. On the agenda today, observing meteorites under the microscope. Jan brought along his meteorites collection - a mars meterorite, a iron meteorite and a rock sample impacted by a meteorite.
Astrophysics of the accretion disk shown around spinning black holes is explained in this movie Gravitational lensing by spinning black holes - see also http:\\www.orionxt12.blogspot.com