An Amateur's Mercury Odyssey

Thanks to the wonders of digital photography and cheap memory cards, you probably lost count of how many pictures you took on your last vacation. Am I right? Heck, these days it's not unusual to delete a third or even half of all the snaps you take to find the "keepers."

But how about going through nearly 40,000 images just to find the 40 best ones? That's what Ron Dantowitz did after an observing run 12 years ago. Teaming up with Scott Teare and Marek Kozubal, he'd gotten some time on Mount Wilson's 60-inch reflector to image Mercury during a particularly favorable elongation on August 27, 1998. The hope was that Mount Wilson's legendary steady seeing would let them acquire diffraction-limited images of the elusive planet. Using off-the-shelf video equipment, they captured the planet when it was 27° up — 40 minutes after sunrise — using a near-infrared filter to increase contrast and the dome to keep sunlight off the telescope.

Even in the raw video, Mercury's 37%-lit crescent looked impressive. But the hard work was only beginning.

Today amateurs routinely employ stacking — selecting and then combining the very sharpest images to yield the best possible detail. Programs like Registax do this almost automatically. But Dantowitz first had to digitize the analog video and then painstakingly find the best frames by hand. "Stacking" as we know it today hadn't been invented yet. The team called its technique "selective image reconstruction."

Fortunately, all that effort paid off. The resulting composite view showed never-before-seen details on a side of Mercury that had been totally missed during Mariner 10's flybys in the mid-1970s. Particularly intriguing was a very bright 100-mile-wide spot, located at 35°N, 300°W, that the team imagined to be some kind of impact feature. The three amateurs published a tidy article in the Astronomical Journal's May 2000 issue, and that should have been the end of the story.

But as the years went by, Dantowitz kept wondering about the nature of that bright feature. In 2008, knowing that NASA's Messenger spacecraft would soon reveal the true nature of his find — and the entire planet, for that matter — he petitioned the International Astronomical Union to have the bright spot named for American composer Aaron Copland. (The IAU names craters on Mercury after artists, musicians, painters, and authors.)

"Copland wrote Fanfare for the Common Man, one of the most recognizable pieces of 20th-century American classical works," Dantowitz noted in his petition. "This Mercury feature was discovered by using common, off-the-shelf commercial video equipment installed by an elementary-school science teacher doing research at a professional observatory. A true discovery that is a 'Fanfare for the Common Man'!"

Last year Messenger did reveal an intriguing bright spot exactly where the Mount Wilson team had spotted it more than a decade earlier. But it's very strange — probably volcanic in origin — so the IAU's planetary moniker-makers and Dantowitz agreed to assign Copland to a true impact basin, 129 miles (208 km) across, adjacent to the mysterious white spot. The naming was announced last week on the Messenger website.

"I finally feel happy about the Mercury work!" Dantowitz exults. Revealing an unseen side of the planet, armed with $100 videocams and sheer determination, was a real triumph. "If only I had then the cameras and computers that I have now," he muses.

(Full disclosure: Dantowitz is now director of Clay Center Observatory, located at the Dexter and Southfield Schools in Brookline, Massachusetts. I teach there part time, and Dantowitz is my boss. No matter, though: he's absolutely fanatical when it comes to coaxing telescopes and instruments to perform at their very best — and then some!)