Cape Breton Weather: “Transit of Mercury”
On Monday, May 9th, we earthlings were treated to a transit of Mercury, an event that happens only about a dozen times each century. From about 8 a.m. to 2 p.m. Atlantic time, Mercury inched its way across the solar disc. I took a number of photos, one of which I present here for your viewing amazement.
Okay, it’s not the most thrilling photo ever. But getting the photo was much less than half the fun, and I need to share the experience in order to recover from it.
The weather started out beautifully: clear skies, light northwest breeze, temperature +2°C on our deck. But the sun was intense. Time out to find a hat. And sunblock. Lather it on.
I knew I couldn’t just aim my camera at the sun and go snap. The sun’s way too bright, and Mercury would be invisible without magnification. So I brought out my birding telescope and tripod, to blow Mercury up. If I looked through the telescope while it was aimed at the sun, all that tightly focused solar energy would fry my eye. However, by projecting it onto a piece of paper a foot or two away from the telescope I’d be enlarging the image and also dimming it. Then I’d take photos of the projected image. A simple plan, easy to carry out.
As usual, the devil was in the details. I leaned a large piece of plywood against the deck’s railing and taped a sheet of paper onto it as a target. One minute later, the morning’s first gust of wind flattened the plywood. I went scavenging for rocks to hold it in place.
It’s hard to aim a telescope without being able to look through it. It takes trial and error, especially error. Worse, my telescope’s dreadful directional controls slip and stick at random, making fine adjustment impossible. I solved this by hitting the telescope with a succession of nudges and shoves, hoping to knock it into alignment with sun and target.
Squinting badly. Another time out to hunt for sunglasses.
The winds blew stronger, the telescope began vibrating, and the image responded by jumping around like the bouncing ball on a singalong video. I tried to stabilize the scope with one hand. I also kept tweaking the image into sharp focus, since any fuzziness would render Mercury invisible. Unfortunately, fiddling with the focus knob often knocked the scope off target. Nudge and shove some more.
In my third hand I held my cell phone, ready to take a photo if a well-focused, unbouncing image miraculously materialized.
The sun moved upward and southward across the sky, but the telescope didn’t, not on its own at least, so my nudging and shoving were almost constant. Focusing, too. And every 10 or 20 minutes the image tracked right off the plywood, requiring that I unstack the rocks, schlepp the plywood, restack the rocks, move the telescope, then re-aim and re-focus it.
Just about the time I had all this down to a system, clouds developed. Puffy fair-weather cumuli, a welcome sight on any day but this one. For a while they toyed with me; then they blanketed the sky, eclipsing Mercury, the sun, and my chances for more photos. But I had prevailed, capturing one useful image!
I hope that readers will find this column helpful whenever they want to photograph a transit. To help you prepare, here’s list (arranged alphabetically) of the scientific techniques involved. They are: aim, blow up, capture, cuss, flatten, focus, fry, hit, knock, lather, lean, nudge, project, render, scavenge, schlepp, shove, snap, squint, stack, stabilize, tape, tweak, unstack.
Practicing these techniques ahead of time will prepare you for transit day. Take my word for it.
Mercury, the dot in the lower part of the photo, moved steadily across the face of the sunon May 9. The cluster of spots in the upper half of the image is a sunspot group.