During the morning of 8th June
2004 Venus passed directly between the Earth and the Sun. The transit – as this
phenomenon is called – was visible from my home in southern Britain where the skies were
clear, if a little hazy, for the whole morning. It is a very rare event. The last transit of Venus
occurred in 1880 (the last one visible from Britain was in 1283) and although the next transit
will be seen until 2012 you will have to wait until 2247 to observe one from
Britain!
The diagram shows how this occurs. (It is NOT TO SCALE – Venus and
Earth are actually about the same size)
Venus moves between the Earth and the Sun and is seen
silhouetted against the bright disc of the Sun. Although Venus is much bigger than the Moon
(about four times the diameter) the light of the Sun is not cut off as it is in an eclipse of the
Sun. This is because Venus is much further away from the Earth than the Moon (about 120
times). You just see Venus as a small black disc moving steadily across the solar surface.
The transit took roughly six hours, I observed the end as Venus left the Sun's disc
at just before 11.20 GMT.
The following series of photographs were taken in
Somerset using my 300 mm Newtonian reflector. The Sun's image was projected onto a
sheet of paper – the diameter of the solar disc being about 20 cm – and then photographed
using a digital camera. (The orientation of the image will have changed during the transit)
