by Ira Polans
Tucson was chosen because it has several advantages over the Northeast. The main one being that there would be a small chance of a cloudy sky on the day of the transit.Another attraction was that Kitt Peak National Observatory planned a special program for the transit. Also, my wife’s parents had retired to the Southwest. This trip would give us a chance to spend some time with them.
The trip from Tucson to Kitt Peak is about 60 miles. However since part of the trip is up the mountain, it takes about 90 minutes to get there. Most of the drive is through the Sonoran desert, which is famous for the Saguaro cactus. To me, any part of the Southwestern landscape is beautiful, and this part of the desert I hadn’t seen before. The last part of the trip is the ascent of the mountain on a winding road. The ascent is about 4000 feet. When you arrive at the summit, you drive past a few domes to the Visitor Center which is at 6875 feet.The Visitor’s Center contains a small museum, a 20” telescope, and a heliostat. For the transit, they also had several amateur telescopes in the courtyard, binoculars, and a sunspotter solar telescope. Of course all the optics had the proper filters. In addition all attendees of the transit program received eclipse shades for safely viewing the sun.
Check-in was at 2:00 pm and the transit began at 3:05 pm. The heliostat projected the image onto a screen about four feet tall. While I knew there would be scopes outside, I thought it would be best to watch second contact here. When the transit began I was surprised by two things. The first was how big Venus appeared against the Sun. The second was how long it took Venus to separate itself from the Sun’s limb. I was aware of the back teardrop affect, but to me and many others in the room, Venus just seemed to stick to the limb.
Historically a transit of Venus was important because it allowed astronomers to figure out how big the solar system really is. Without an event likes this, the best astronomers could do was measure the relative distances between planets. By using trigonometry, parallax, and accurate timings of second and third contact, along with Kepler’s third law they could finally figure out the actual distance from the Earth to the Sun. And once they knew that they could figure out the distances to the planets.
To give the attendees a better idea of the effort involved in applying this technique, Andrea Wulf lectured us about her book “Chasing Venus: The Race to Measure the Heavens”. In her lecture, Andrea told us about how 18th century astronomers worldwide worked together to capture the information need to make the calculation during the transits of 1761 and 1769.
As previously mentioned the Visitor’s Center has a 20” telescope. As the Sun began to set, the telescope was put into use. Rather than look at the Sun and the transit, we had a chance to see Betelgeuse and Sirius. This was possible because the telescope is computerized.
During the trip I had the opportunity to tour one of the remaining Titan II missile silos and visit the Pima Air and Space Museum. Both of these are in the Tucson area.