Photographing the Rare Transit of Venus

A pinhole camera is an inexpensive means to capture images of the Sun, including the transit of the inner planets, Venus and Mercury.

When a planet passes in front of a star (e.g., our Sun) between the viewer and the star, one can see the dark spot passing across the bright disk of the star. That is, by the way, how some exoplanets are discovered: the light from the star momentarily lessens and repeats this with a periodic interval (corresponding to the planet’s orbit). For us on Earth there are two transits of our sun: the planets Venus and Mercury. Only those planets get between us and the sun.

Transits of Venus are among the rarest of all predictable astronomical phenomena. There were two in the 21st century: 8 June 2004 and 6 June 2012. I captured the one in 2012 when we lived in Charlotte NC. The previous transits were in 1874 and 1882 and the next transits are not until 2117 and 2125. It is likely that my children and possibly my grandchildren will not live to see those. So, very rare event and I got a photo (see below). A good article on transits of Venus can be found here.

I didn’t have (and still do not have) a solar filter for my camera so I needed another way to see the transit. A pinhole camera is an inexpensive way to get an image of the sun without burning out the optics on a camera (see this article that explains all about pinhole cameras, aka camera obscura). The pinhole camera can show the planet crossing the disk of the sun. I built a pinhole camera using FedEx cartons, a piece of metal with a hole drilled in it (at one end of the tube) and an image pad at the other end to focus the image. My 35mm DSLR on a tripod captured the image formed by the pinhole camera. This was a bit crude but it worked, MOL.

In the photo Venus appears as a black dot moving across the face of the Sun. See it at lower left of Sun’s image (about 5 o’clock at edge of disk). The black and white inset at lower right gives a slightly better view. The time of the transit was on the order of an hour.

The experience with my “solar pinhole camera” back in 2012 led me to improve the camera and I got to use it today for the annular solar eclipse. See my post on that here.

LEFT: Steve with homemade pinhole camera (in Charlotte NC, June 2012)
MIDDLE: Image of Venus passing in front of Sun (small black dot at 5 o’clock edge of solar disk); black and white inset at lower right shows the planet image better.
RIGHT: Close up of the image end of the pinhole camera and the DSLR camera I used to get a permanent photo.