Transit of Mercury
On May 9, a last-minute chase into clear skies netted me a view of the rare transit of Mercury across the Sun.
The forecast called for typical transit weather – clear the day before, and clear the day after. But the day of the transit of Mercury? Hopeless at home in Alberta, unless I chanced the prospects of some clearing forecast for central Alberta.
As the satellite image below, for 8:30 a.m. MDT on May 9, shows, that clearing did materialize. But I headed west, as far west as I needed to go to be assured of clear skies – to central BC. Kamloops in fact.
I stayed at the Alpine Motel, got a great room as the end, and set up in the parking lot away from traffic. Not the most photogenic of observing sites, but I was happy! I had my clear skies!
I set up two telescopes, above: a 130mm refractor to shoot through, and an 80mm refractor to look through. Both with dense solar filters!
Both worked great. However, low cloud prevented me seeing the Sun as soon as it cleared the eastern hills. So this was my first good look, below, at the transit as the Sun rose above the clouds.
There it was – the fabled “little black spot on the Sun today.” Mercury is the dot at lower left, with a sunspot group at upper right. This was the first transit of Mercury since November 8, 2006. We see only about 13 Mercury transits a century, so in a lifetime of stargazing (the Sun is a star!) even the most avid amateur astronomer might see only a handful. This was only my third transit of Mercury.
This was the view, above, a little later, as the Sun entered more assuredly clear skies. From about 7 a.m. PDT on, the Sun was in the clear most of the morning, with just occasional puffy clouds intervening now and then.
I shot still images every 30 seconds, to eventually turn into a time-lapse movie (after a ton of work hand registering hundreds of frames!).
But for now, I’ll be content with this composite of 40 frames, below, taken at 7-minute intervals. It shows the progress of Mercury across the Sun over the last 4.5 hours or so of the event, until egress at 11:38 a.m. PDT.
This motion is due to Mercury’s movement around the Sun. A transit is one of the few times you can easily see a planet actually orbiting the Sun.
In this composite, the disks of Mercury are not all perfect dots. The wobbly seeing conditions distorted the images from frame to frame. But I used the actual images taken at that moment, rather than clone some perfect image across the disk to simulate the path.
To wrap up, here’s Mercury Transit: The Movie! I shot several HD and zoomed-in “crop mode” movies at the beginning of the transit and again at the final egress. Commentary is from me talking live into the camera mic as I was shooting the clips. Background noise is courtesy Pacific Drive and the Trans-Canada Highway!
Enjoy, and do enlarge to HD and full-screen for the best look.
The next transit of Mercury is November 11, 2019. If you are hoping for a transit of Venus, good luck. The next is not until December 10, 2117!
– Alan, May 15, 2016 / © 2016 Alan Dyer / www.amazingsky.com