February 25, 2020

Waiting for Mercury: Tales of Transits

Our humble station.

There’s another insidious danger that awaits unwary solar astronomers.

This coming Monday on May 9th, the planet Mercury transits the fair face of our host star as seen from our Earthly vantage point. Unlike, Venus, Mercury is tiny, meaning amateurs everywhere will be scrambling to make solar filters for their telescopes this weekend.

It also means that you can expect to hear lots of warnings on the perils of solar observing to come. Yes, you can fry your eyes instantly without proper protection, namely a projection system or a solar filter designed to observe the Sun securely affixed to the front of your scope.

But what we’d like to mention, as we enter this coming pre-transit preparation weekend,  is another danger we courted during the last transit of Mercury on November 8th, 2006.

This was less than a month from our retirement from the U.S. Air Force and departure from Davis-Monthan Air Force Base and Tucson, Arizona. I found myself scopeless, as we prepared to strike out on our backpacking trip ’round the world.

Needless to say, I jumped at the chance to do one last public event at the Flandrau Observatory on the University of Arizona campus. Heck, I even made a Baader solar filer mask for a loner refractor from the observatory on weekend prior, just for the event.

The day dawned hot and clear. For Arizona, the transit occurred late in the heat of the afternoon. I checked out of work early, lest any last minute emergencies strand me prior to the start of the transit. Jumping into civilian clothes out of uniform with gear stashed in the back of my Jeep Wrangler, I dashed across town to the university.

Now, the 2006 transit of Mercury was almost five hours long. By definition, this means standing out in the Sun for a similar duration. All the while, we went through the familiar public observing drill: tweak the scope, center Mercury, direct folks to the eyepiece, answer questions, repeat. Crowds were bigger than expected. The angry Arizona sun beat down on us hapless scope operators, its blaze scarcely dimmed by diminutive Mercury.

Don’t worry, I made it. Like the good solider we are, we never abandoned our post or our duty to the curious public. ‘Do it for the kids,’ we thought. ‘The kids love Mercury, they gotta see Mercury!’ We secretly thanked Mike Terenzoni for the very few brief minutes afforded to duck inside the Flandrau and in to the cool shade within, under the pretense of seeing Mercury on the big screen from the live feed from the scope located in the dome of the Flandrau observatory above.

We drank as much water as we dared. Solar observing is something like a third world bus ride; guzzle down too much fluid on top of morning coffee and a diet Coke, and you’ll be hunting for a toilet every two minutes. As with a long dusty bus to Bangkok, said bathroom might be hours down the road when you’ve got a line around the block at your scope. The solution: drink H2O when thirsty, but only just enough to slake your thirst.

Even in November, Tucson in the late afternoon can indeed feel like the surface of Mercury. In the current epoch, transits of Mercury can occur in the months of November and May, and I truly feel for those brave souls crewing scopes in southern Arizona next week in the heat of May.

It was only hours later back at billeting when I realized I probably came close to borderline heat stroke that day. Denial is part of the package, and it seemed to take hours (and pouring an icy cold bath) to really cool down. I’d run miles in the deserts of Kuwait, but can attest that standing in the afternoon sun for hours can heat a body up just as easily.

The solution? Make sure you pack your own shade Monday, be it a small portable canopy or tripod mounted umbrella to step under. The ‘kids want Mercury, and we give it to ‘em,’ but don’t fry for the cause!


  1. [...] and shared the Sun safely with the world via social media online… and folks headed our admonishment to stay cool and hydrate, and no reports of heat stroke from solar observers were noted. A lonely world… Image [...]

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