Bernardi told the Honolulu Star-Bulletin he was looking at images taken with the Canada-France-Hawaii Telescope at Hawaii's Mauna Kea observatory when he noticed an object that was "a bit fuzzy," with a tail estimated at more than 13,000 miles long.
It was Halloween night, he said, and "It was really weird."
The first thing he did was check to see if it was new. He found there had been no comets previously observed in that part of the sky, about 280 million miles from Earth.
The comet, the first to be discovered at Mauna Kea, was reported to the International Astronomical Union, which named it for its discoverer: P/2005 VI Bernardi.
The comet orbits the sun about once every 10 years and does not come close enough to the Earth to be seen with the naked eye, the Star-Bulletin said.
Bernardi is a member of a University of Hawaii team working in a NASA-funded program to find potential "killer asteroids" passing close to Earth.