Sudden Changes in the Motion of Jupiter's Great Red Spot During 1962

Abstract

Fifty-seven visual determinations of the System II longitude of Jupiter's Great Red Spot, made during the last four months of 1962, have been plotted and analysed. The totally independent testimony of a number of observers provides what appears to be overwhelming evidence that during about three weeks, centred near October 20, the longitude of the Red Spot, which previously and subsequently was sensibly stationary in System II, increased by approximately 4°. On the evidence available it seems impossible to extend the duration of the transition beyond a maximum of five weeks. These conclusions augment rather than conflict with those recently published by B. A. Smith and C. W. Tombaugh, which were derived from the measurement of a number of photographs of Jupiter, obtained by them during the same period.