Comet Tempel-Tuttle (1866 I)

Dr. Joachim Schubart, Astronomisches Rechen-Institut, writes: "I have made an attempt to get a prediction for the return of Comet Tempel-Tuttle, 1866 I, which is related to the Leonid meteor stream. Identity with the Chinese Comet of 1366 was assumed. With several hypotheses for the period the comet was computed back from 1866 over 15 revolutions under the influence of the sun and the outer planets. A first reliable orbit could be derived from this, which pointed to good observing conditions in 1699. An observation by G. Kirch from 1699 Oct. 26 can be well represented by a second orbit close to the first. Elements for 1965 and an ephemeris are given here from the second orbit on a separate sheet. The variation, if added with the sign given, leads back to the first orbit. It corresponds to Delta T about -6 d and gives an estimate of the uncertainty of the method. Observing conditions were also good earlier this year. T = 1965 Apr. 25.28 ET Peri. = 172.57 e = 0.90443 Node = 234.43 1950.0 a = 10.2699 Incl. = 162.71 1965 ET R. A. (1950) Decl. Delta r Variation Mag. May 30 2 47.1 + 9 55 1.95 1.13 -12m2 -125' 12.7 June 1 2 46.3 + 9 24 3 2 45.4 + 8 53 5 2 44.5 + 8 20 7 2 43.6 + 7 47 9 2 42.6 + 7 12 1.85 1.22 -12.2 -128 13.1 11 2 41.5 + 6 37 13 2 40.4 + 6 0 15 2 39.2 + 5 21 17 2 37.9 + 4 41 19 2 36.5 + 3 59 1.71 1.31 -12.5 -135 13.4 21 2 35.1 + 3 15 23 2 33.5 + 2 29 25 2 31.8 + 1 41 27 2 29.9 + 0 50 29 2 27.9 - 0 3 1.55 1.42 -13.1 -145 13.7 July 1 2 25.7 - 1 0 3 2 23.3 - 1 59 5 2 20.7 - 3 3 7 2 17.8 - 4 10 9 2 14.7 - 5 21 1.38 1.53 -14.2 -158 14.0 Mag. = 10.5 + 5 log Delta + 15 log r