Preparing

Safety

The apparent semi-diameters of Venus and the Sun are 29 arc-seconds and 945 arc-seconds respectively. This 1:32.6 diameter ratio results in an effective 0.001 magnitude drop in the Sun's integrated magnitude due to the transit. This simply means that the Sun will be as dangerous for our eyesight at the time of the Venus Transit as it is on any normal day, when there is no planet in front of the solar disc.

NEVER LOOK DIRECTLY AT THE SUN WITH UNPROTECTED EYES - THIS MAY CAUSE TOTAL BLINDNESS WITHIN SECONDS! ALWAYS BE SURE TO USE PROPER OPTICAL FILTERS TO PROTECT YOUR EYES.

The use of #14 shade welding glass or eclipse shades will permit a large number of people who do not have specialized equipment to observe this event. However, as the planet approaches the limb of the sun, subtleties like the black drop effect may not be discernible.Pinhole projectors are a safe, indirect viewing technique for observing an image of the sun. While popular for viewing solar eclipses, pinhole projectors suffer from the same shortcomings as unmagnified views when Venus approaches the edges of the sun. Small features like the black drop effect and the halo around Venus while it straddles the solar edge may not be discernible.

Courtesy: European Southern Observatory

You may project a magnified view of the sun through a telescope onto a surface, but the technique often has its own limitations. For example, large reflector telescopes can generate too much heat by concentrating a lot of the sun's energy on the secondary mirror and eyepiece. Likewise, Schmidt-Cassegrain telescopes can experience too much heat build-up as the light bounces internally. Also, magnified projections usually have an exposed focal point beyond the eyepiece where bystanders could inadvertently burn themselves. Constant attention is required.

The transit of Venus is perhaps best viewed directly when magnified, which demands an appropriate solar filter over the large end of the telescope. Do not use small filters that fit over the eyepiece, for the concentrated sunlight can shatter them. The sun's energy must be attenuated before it enters the telescope. A filtered, magnified view will show the planet Venus, the "black drop" effect, and sunspots.

No matter what technique you use for viewing the sun, do not stare continuously at the sun! Always give your eyes a break.