That night, to test the newest of his telescopes, Stevens had decided to look at a series of objects called globular clusters which are plentiful in the portion of the Milky Way visible in summer months.
By this time, Stevens and Bopp had worked out a familiar routine: Stevens, who knows the sky well and can locate galaxies and star clusters and nebulae fairly quickly, would move the telescope into position using a low-powered eyepiece to find his quarry. Then he'd quickly exchange for a higher-powered eyepiece and call Bopp over to take a look. Stevens admits that he was often so eager to show Bopp a celestial object, he'd only take the most cursory look at the field of view himself.
One by one, Bopp and Stevens compared the globular clusters in the constellation of Sagittarius. The clusters each contain tens of thousands of stars, but are so far away--many thousands of trillions of miles--that they've been likened to little piles of salt on black velvet.
They're remarkable objects, but for the casual observer, if you've seen one globular you've seen them all. The experienced eye, however, sees slight variations, and when Tom Bopp put his eye to the telescope to see what Stevens had lined up--a globular cluster named M70--he was looking for such subtleties. And that's why he was surprised to see something unusual.
Bopp says that on the extreme edge of the telescope's field of view, he could see a small patch of luminosity just drifting into sight. The Earth's rotation, carrying along Stevens' stationary telescope, was bringing another piece of the sky into view, and with it an unidentified object.
"Hey, Jim," Bopp remembers saying, "is there supposed to be something else by M70?"
Stevens came over for a look. He says that the second he saw that dim speck, he knew.
Four hundred miles away in Cloudcroft, New Mexico, Alan Hale already had had the object in his sights for 15 minutes. Hale, a seasoned comet observer, had also been looking at M70 when he saw the dim patch of light nearby. And even though it was his first discovery of a new comet, he knew just what to do about it. He calmly made a drawing of the object.
In Arizona, near-panic had set in.
Nothing makes an astronomer's pulse race like the thought of discovering a comet. Amateurs make other contributions to the science of astronomy: They measure the fluctuations of stars which vary in their brightness; they monitor the weather on Mars, Jupiter and Saturn; and they discover exploding stars--called supernovae--in distant galaxies. But nothing compares to finding comets.
No other worlds, after all, carry the names of their discoverers.
In amateur astronomy, comet discoverers are royalty. Those with multiple discoveries to their credit are sanctified. Even the general public is familiar with the name of Edmund Halley, who was the first to realize that several of history's greatest comets were actually one object which kept coming back every 76 years.
The incentive to find a comet can turn an otherwise rational stargazer into a gibbering wreck. Amped-up astronomers call in false alarms: They see something that looks like a distant comet and scramble to claim credit for it, only to find that it's a nebula that's been there for millions of years, or a comet which was claimed a few days before.
Attaching one's name to a speeding comet requires a well-defined and long-accepted protocol of verification, notification and luck. Such was the task facing Tom Bopp and the other astronomers who were gathering to help him verify the discovery.
Meanwhile, Jim Stevens' mind raced. Would he get co-credit? It was his telescope, after all, and even if he hadn't seen it first, he'd pointed the scope at the comet. There was no question whose name would go first, but Stevens says at this point, he felt he was working to confirm the existence of Comet Bopp-Stevens.
His companions that night figure he must also have been consumed with another thought.
Why hadn't Stevens noticed the comet himself?
Although Jim Stevens is an experienced observer who can quickly direct his telescope toward numerous celestial objects, he's not a member of an even more specialized, dedicated cabal: comet hunters, the hard-core types who may spend more than a thousand hours at the eyepiece before hitting pay dirt.
A separate breed, comet hunters memorize star charts down to excruciating detail and blanket likely areas of the sky night after night with orderly searches.
With both professionals and amateurs competing in the game, it's unusual today for the casual observer to stumble across an undiscovered comet. But several circumstances conspired to work in Bopp's and Stevens' favor: The unusual size of Hale-Bopp made it visible from an incredible distance and, consequently, in a part of the sky that comet hunters would have thought unfruitful. But even more fortunate was the comet's accidental placement so close to a well-known celestial object--globular cluster M70.