The beginning and the end of observation
Although the whole Venus’s transit takes almost 6 hours, the most interesting things can be seen in the first and last twenty minutes. Why? Besides four contactpoints, important for calculation of a parallax, it´s also a very special show, which presents itself.
The Black Drop Effect
This effect can be seen thanks to the telescope refraction and to reflection the athmospheres of both planets. It is visible in time, when the whole Venus appears in front of the Sun and also in time, when approaching the Sun at the end of the transit again. In the first case it looks like Venus doesn’t want to leave the Sun’s edge, in the second one it looks like like planet want to suck it – then the Venus circle elongates itself to form, which resembles a „black drop“.
The luminous Aureola
It appears around Venus before it gets on the Sun disc or before it leaves it. It is also connected with the deep atmosphere of the planet, in which the Sun rays are dispersed and that´s why it is possible to see it. Sometimes it could be observed also in the time, when the planet occurs in the tight closeness of the Sun.
Picture 1 (I and II shows the Black Drop Effect and III the luminous
Aureola)