C/1967 Y1 (Ikeya–Seki)

Discovery and observations

C/1967 Y1 was the 14th comet discovered in 1967 when both Kaoru Ikeya and Tsutomu Seki spotted on the evening of 28 December. At the time, it was a 9th-magnitude object within the constellation Ophiuchus. The comet's position remained circumpolar throughout its last perihelion, thus giving astronomers a rare opportunity to observe it all night long.

It reached its peak brightness of 6.3 on 4 February. By 25 February 1968, the comet faded to an apparent magnitude of 7.1 and developed a very faint tail. Photometric spectroscopy of the comet's tail together with comets C/1968 L1 and C/1968 N1 has shown its forward scattering to be gray in the 3500–6300 Å spectrum, in contrast to the reddening of the dust tail seen in other comets. The comet was last observed from the Kitt Peak Observatory on 4 November 1969.