  The main observations of 1761 by M. Lomonossov and those that followed are
recalled by extending the discussion to other remarkable visual observations of
the passages, then with more and more powerful imagers producing images in
profusion. The modern treatment of parasitic effects is briefly recalled by
focusing on the expert observation of 1761 which has recently been widely
commented on and criticized. It included a spurious effect called the "black
drop effect". The shell or aureole or atmospheric ring of Venus observed
outside the solar disk is considered with reference to the today parameters of
the Venus atmosphere. The contacts during the transit are discussed taking into
account effects of scattering, absorption and the dominant effects of the
refraction at the small angular distances found to be comparable to a fraction
of the angular dimension of the planet. Modern observations of the 2004 and the
2012 transit are tentatively discussed to elucidate what is the arc of
Lomonossov?
