Airborne photographic observations of Comet Ikeya-Seki, 1965 VIII

A photographic history of Comet Ikeya-Seki, 1965 VIII, is presented for 23 to 26 October 1965, three to six days, respectively, after perihelion passage. The photographs were taken from a NASA jet airplane at 40000 ft over the Pacific Ocean near the Hawaiian Islands. From these photographs, measurements are made of the tail length and also, for the latter two days of the period, of the tail's curvature and of the movement of a feature in the midtail. On 23 and 24 October, the tail length was at least 20 and , re- spectively. On 25 and 26 October, it was 100 50', and 130 50', respectively. (The time of day on all four days was UT.) On the latter two dates, indications of the curvature of specified sections of the tail are obtained by measuring the deviation of the midpoint of that section from the great circle arc between the ends of the section. For a 100 50' length of the tail on 25 October, such a curvature was 45 min of arc; for an equal length of the inner tail on 26 October, the curvature was 32 min of arc. Such measurements indi- cate that the inner, younger part of the tail is less curved than the older, outer part. Also between those dates, a prominent dark band in the midtail moved 20.25 farther away from the head.