Venus Transit 2012
Next Tuesday, June 5th, Venus will cross the face of the sun in a rare celestial event called a transit. Venus transits occur on a regular schedule in pairs eight years apart, with 105.5 years from June to December pairs, and 121.5 years from December to June pairs. The last transit was in June 2004; the next after this coming one will be in December 2117.
Historically, Venus transits were used to determine the distance from the Earth to the Sun using parallax measurements, judged by the difference in time of start and end of the transit measured from widely separated points of Earth. Knowing the distance between observation points, Earth-Sun distance could then be calculated with the ingress/egress times. Since being predicted by Kepler in the 1600s, these events have led to many cross-planet expeditions, including Captain Cook’s first voyage, during which he observed the transit from Tahiti. Although the advent of radar now allows for more precise measurements than parallax, this century’s transits will be used to improve exoplanet study methods. In fact, the Hubble itself will be watching this year, using the Moon as a giant mirror!
The following link explains various methods of watching the sun safely during this and other events:
So far, I’ve only tested the telescope filter, open projector, and pinhole projector. Pinhole is by far the simplest and it’s cheap (but image may be small, I only tried one size); I used an old shoebox and a bit of foil. Filters are nice to have, but can be expensive. During the recent solar eclipse, my chapter noted better clarity with the open projector (a beautiful, crisp image) than the filter provided, although that may just be a difference in the telescopes themselves rather than method. The projector only requires a white background and proper positioning, so it’s definitely more affordable than the filter.
The transit starts around 1700 (5pm) from Altus, OK perspective, but that time will differ at other locations. I recommend using astronomy software that allows time-travel; I used the SkySafari app, Stellarium is another good program and it’s free, etc. Good luck, and may you have clear skies!
Written by William McCarter-President of S.P.A.C.E. Association of Altus, OK