Taipei cigar-shaped object and Tsai Chang-hung's observatory photograph

Summer, 1967. The Taipei City Observatory stood at Yuanshan, in Taipei. Its chief was Tsai Chang-hsien, who would one day have minor planet 2240 named in his honour. Tsai Chang-hsien did not believe flying saucers existed in this world, but kept a great interest in UFO theories. The chief's younger brother, Tsai Chang-hung, was a teenager at the observatory.

28 June 1967. Evening. Tsai Chang-hung saw a bright dot make an abrupt 90 degree turn near the Big Dipper. Tsai Chang-hung grabbed a 16mm camera and called the chief to come and look. The dot had already disappeared. Then it came back. As soon as it reappeared, Tsai Chang-hung snapped three photos. The object hovered above Guanyin Mountain in New Taipei City for about 30 seconds. Then it was gone.

Taiwan Ufology Society investigator Ho Hsien-jung later gave a closer description. Through the observatory's five-inch naval telescope, it was a disc. Its whole shell gave off intense orange-red light, brighter than Vega. The lower part was deep black and gave off no light. The upper parts were pale white and luminous. From a distance, Ho wrote, it looked like a cigar. In Ho's account it flew from north-east to south-west, stopped motionless for about ten seconds, and was in view for about two and a half minutes. At about 9:15 pm it appeared again, over the southern part of Taipei, for about fifteen seconds.

Across the city, others saw it too. Citizens phoned the observatory, which was unable to explain the phenomenon. The United Daily News reported a "strange object flying around in the sky", a "pale red, cigar-shaped object that emitted bright light."

The Central Weather Bureau quickly said the "strange object" was one of its weather balloons. According to Ho, the bureau's statement gave details. A high-altitude wind-measuring balloon released at 8:24 pm, one minute before the first sighting. It carried a lantern, travelled north-west to south-east, and shone about as brightly as a second-magnitude star.

Ho was not convinced. The balloon went the opposite way. It was too faint. Ho maintains that they were two different objects and that the bureau was trying to cover up the event.

Tsai Chang-hung told no one. Tsai Chang-hung "wasn't sure what it was and worried about being ridiculed." The photographs surfaced only after TUFOS was founded. They were displayed on 4 May 1996, and the Liberty Times ran them the next day under the headline "Taiwan's earliest UFO photo taken 29 years ago?" The pull quote read: "That flying saucer was multi-colored." Tsai Chang-hsien said it was unlikely to be a balloon. The chief would not call it an alien craft, but called it an "unidentified flying object."

The pictures carry a caveat. The lens could not be aimed properly, and about a quarter of the object was cut off. In 1996 the image was restored, with spots removed and the missing part rebuilt by mirroring its symmetrical shape. The best-known version is partly reconstructed.

TUFOS called it "Taiwan's first UFO photo", and Ho called it the most famous photo of a UFO in Taiwan. The title is contested. Chih Chung-chieh's 1973 picture had been thought the earliest, and the Taipei Times later pointed to an even older one, taken by Wang Shi-lin in Taitung City in 1961. Ho, who logged more than 50 Taiwanese sightings, held that 95 percent of reported UFO sightings can be explained. This one, in Ho's view, is not among them.