Transit of Venus - June 5, 2012
The last transit of Venus across the face of the sun this century was due to occur on the afternoon of June 5, 2012 and I was hoping to be able to see it and to photograph it. The most straightforward approach to doing this would be to use my Celestron C8 with a solar filter. But...The transit was scheduled to be late afternoon (~6pm} on the east coast AND the east coast is always cloudy AND the C8 is a big pain to ship. Thus, I thought of my brother's house near Palm Springs, California. It is almost always cloudless there and, the transit would begin 3 hours earlier (~3pm) giving a much longer time for photography. Also, I thought of my recently constructed and highly portable 8" dob. I realized that all I needed to do was to generate a solar filter for the dob and the trip would become easy. So... How do you put a solar filter on a dob?
How do you put a solar filter on a dob?
| Using a square of black foam core to cover the opening, I cut a circle ~100 mm in diameter, off-axis. Using a nominal 80 mm Bader solar filter (Which had an actual 92 mm diameter filter)that I bought for $50, I put three 'holders', generated from wood and glued and screwed to the foam core. The foam core, itself, was attached to the scope by two #6 machine screws into brass threaded inserts attached to posts that I attached to the two truss tubes. The far corners were velcroed. This all worked perfectly. |
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The Transit of Venus - June 5, 2012
As expected, Jun 5 arrived bright and sunny with temperatures at a mild 92 degrees. My brother's back yard faces southwest and had a pretty good western horizon. I used a 30mm Celestron Ultima eyepiece that gives 42x and 1.2 degrees field-of-view. Using this setup I have done afocal photography by putting my Canon A540 Point-and-Shoot on a tripod and placing it in font of the eyepiece. I like the A-series of Canons since you can operate them manually. So I played (long in advance of the transit) with f/stops and exposure times and iso values to get a good exposure of the sun with this set up. I started taking pictures at 3:00 pm and took pictures every so often (not very scientific) till about 7:00 when the wind whipped up and made further photography impossible. Nevertheless, I got about 4 hours of the transit.
Time Series of the Transit of Venus
| Several sunspots are visible on the face of the sun. In the upper left, taken just after 3pm, Venus is just beginning to enter the picture on the left. On the upper right Venus is fully silhouetted against the sun. In the middle two pictures Venus makes its way deeper into the disk of the sun. In the final picture, taken about 6:30, or so, Venus is approaching one of the sunspots. This was the last picture I was able to get although we watched till the sun went down just before 8pm. |
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| This is my nieces's husband who came over to see what all the fuss was about. |
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So it was a great trip. I got to visit with relatives, enjoy my grand niece's 15th birthday, visit with old friends, AND get a great view and photos of this very rare event.
Guess what? - The east coast was totally clouded out. Who knew?
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