May 9th – the Transit of Mercury across the Sun. I couldn’t see the last one, several years ago, since the sun was so dimmed by haze, after the solar filter, there was no sunlight left.
The sun broke through the stratocumulus clouds about 7:10am and I used my 8-inch dobsonian reflector telescope to watch Mercury move onto the solar disk. Because of turbulence and thermals, the edge of the sun looked very wavy, as if the sun had a scalloped edge. Mercury seemed to stay attached to the edge of the sun for a long time, well after the entire disk was in front of the sun.
I took a few photos with my Canon XS camera in place of an eyepiece (‘prime focus’) and a white light solar filter (see below).
Then I drove to work with my 60mm f/11 Orion refractor. I was surprised I didn’t have to convince security that it was ‘take our telescope to work day’. Viewing diagonally through the laminated glass and various thicknesses of cirrus clouds was difficult, since the sun was getting high in the sky by 10:30. I found the best way to see a faint impression of the sunspot group and Mercury was to project the image of the sun onto a white sheet of paper tacked up on a partition in shade – something hard to do outdoors. The 25mm (low power) eyepiece was best, but contrast and resolution was poor. By noon, a layer of altostratus clouds moved in from the south and covered the sky where the sun was, ending our viewing.
While I drove to work, it was fun to hear the FM stations talk about the transit. WCBS-FM’s morning show host was complaining his co-hosts were very quiet, ‘looking at a tiny dot on a computer screen’, because they were fascinated by NASA and Space.com’s coverage of the transit.
PS I’ve done astronomy through the glass at work before. We’ve observed the Moon, a comet and last December, the Moon next to Venus.
|Click to see Venus as the dot to the upper left of the Moon. Dec 7 2015 250mm Canon XS 1/640 second exposure at f/11 and ISO 400.|