Veteran comet hunter discovers 11th comet

Still in the position where he first spotted the comet, Don Machholz’s 18-inch Dobsonian awaits another night of comet hunting in his backyard observatory. Don Machholz photo

The quiet pre-dawn hours of March 23, 2010, found veteran comet hunter Don Machholz systematically scanning the eastern sky, his eyes restlessly moving through the heavens like the “great bear” itself. Alone in the darkness, he searched for anything out of the ordinary. This was business as usual for Machholz, who has logged well over 400 consecutive months seeking out elusive dust balls in space. But this observing session would prove to be much more than just another late night spent basking in the glow of ancient photons.

From the backyard of his Northern California home, Machholz was methodically sweeping the early-spring skies with his 18-inch Dobsonian telescope when he caught a glimpse of something unusual. Peering through the eyepiece, he spotted a faintly glowing speck hiding among the stars near the great square of Pegasus. Turning to a reference sheet of known comets, he anxiously checked to see if this mysterious object was already on the list. He then moved on to his star atlas but found nothing.Returning to the eyepiece, he attempted to find it again — a potential challenge because his telescope is not equipped with a clock drive. His eye was quickly drawn to the object again. At 5:37 a.m., a rush of adrenalin coursed through him as he placed a tiny X on a vacant spot of the star chart.

Under the rapidly brightening sky, with only his faithful yellow Lab by his side, Machholz swapped out the eyepieces and made a sketch of the object, and then a second under higher magnification to see if the object displayed any motion. But within 5 minutes, the magnitude 11 object had vanished in the early morning twilight, ending the pursuit.

He woke his wife, giving her the news of his overnight discovery, and then fired up his computer and double-checked the object’s position in his astronomy software. His heart raced a bit when he recognized the pattern of stars he’d seen through his eyepiece, but nothing that could be mistaken for a comet in that region of the sky. On the Central Bureau for Astronomical Telegrams (CBAT) website, he ran a search for any comets in the area, but none returned. Although movement had yet to be confirmed, Machholz felt confident enough to submit the discovery to CBAT.Over the course of the next two nights, bad weather foiled Machholz’s attempts to confirm the object’s movement. Spring rains had returned to the Sacramento Valley, and dense clouds obscured the sky. But in the early morning hours of March 26, the clouds parted and Machholz was again able to track down and gaze upon the mysterious object. It had clearly moved since his initial observation, and he quickly calculated a progression of 2° a day in its journey around the Sun. It wasn’t until that moment that he was certain he had found another comet.The discovery of what is now officially known as C/2010 F4 (Machholz) marks the 11th for the indomitable backyard astronomer. His last find, C/2004 Q2 (Machholz), was made 6 years ago. More than 600 observing hours later, yet another comet bears his name.

Machholz holds the record for visual comet discoveries in the United States and ranks second in the world behind Australia’s William Bradfield. But it’s more than sheer luck that makes Machholz one of the world’s foremost comet-hunters. He has spent more than 7,600 hours systematically searching the night sky since he began January 1, 1975. Most of Machholz’s discoveries were made with a modest 6-inch reflector. It was only recently that he graduated to an 18-inch Dob.

With this, his 11th discovery, Don Machholz proves that comet hunting is still well within the grasp of the backyard astronomer.