National Astronomical Observatory of Japan
This comet was actually the second Comet Hyakutake; Hyakutake had discovered comet C/1995 Y1 several weeks earlier. While re-observing his first comet (which never became visible to the naked eye) and the surrounding patch of sky, Hyakutake was surprised to find another comet in almost the same position as the first had been. Hardly believing a second discovery so soon after the first, Hyakutake reported his observation to the National Astronomical Observatory of Japan the following morning. Later that day, the discovery was confirmed by independent observations.