THE ASTRONOMER Electronic Circular No 540 1991 July 13 16.24UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP, England. Telephone: (0256)471074 Int:+44256471074 Telex: 9312111261 Answerback: TA G JANET BOXES: GMH at UK.AC.CAM.ASTRONOMY.STARLINK or GUYH at UK.AC.SUSSEX.CLUSTER TELECOM GOLD: 10074:MIK2885 PRESTEL 256471074 ------------------------------------------------------------------- PERIODIC COMET MACHHOLZ (1986 VIII) Further to the note on E537, this comet has now been observed by A.C.Gilmore and P.M.Kilmartin July 3-5 with the 0.6-m reflector at Mount John University Observatory. The comet's m2 magnitude appears to have risen from 16 on July 3.7UT to 14 on July 5.7. Brian G.Marsden has computed the following elements based on 93 observations 1986-1991: Epoch = 1991 July 3.0 ET T = 1991 July 21.9824 ET Peri. = 14.5287 e = 0.958370 Node = 93.8227 1950.0 q = 0.125545 AU Incl. = 60.1472 a = 3.015711 AU n = 0.1881999 P = 5.237 years IAUC 5301 Revised ephemeris by Hurst using a program by N.James: m = 13.0 + 5.0 log R + 12.0 log r Date R.A. (1950) Dec. R r Elong Mag. Motion h m o ' (AU) (AU) o "/hr P.A. 1991 July 13.00 6 34.88 +3 55.1 0.992 0.380 21.7 7.9 361 46 14.00 6 41.86 +5 37.0 1.007 0.348 19.8 7.5 367 45 15.00 6 48.95 +7 21.7 1.024 0.316 17.8 7.1 376 45 16.00 6 56.22 +9 10.3 1.042 0.284 15.8 6.5 389 45 17.00 7 3.78 +11 3.6 1.060 0.251 13.6 5.9 406 45 18.00 7 11.79 +13 3.0 1.080 0.217 11.4 5.2 431 45 19.00 7 20.50 +15 10.4 1.100 0.185 9.0 4.4 465 45 20.00 7 30.25 +17 27.0 1.118 0.156 6.4 3.6 511 46 21.00 7 41.54 +19 51.8 1.131 0.134 3.7 2.8 563 49 22.00 7 54.62 +22 16.2 1.134 0.126 2.3 2.5 593 54 23.00 8 9.03 +24 23.5 1.126 0.134 4.2 2.8 580 60 24.00 8 23.84 +26 2.9 1.108 0.157 6.8 3.6 543 67 25.00 8 38.47 +27 15.2 1.087 0.186 9.4 4.4 507 72 26.00 8 52.80 +28 5.9 1.065 0.218 11.7 5.2 482 77 27.00 9 6.86 +28 39.8 1.045 0.251 13.9 5.9 464 82 28.00 9 20.69 +28 60.0 1.026 0.284 16.0 6.5 452 85 29.00 9 34.32 +29 8.8 1.009 0.317 18.0 7.0 444 89 30.00 9 47.77 +29 7.7 0.993 0.349 20.0 7.5 438 92 31.00 10 1.02 +28 57.8 0.980 0.380 21.9 7.9 433 94 1991 Aug 1.00 10 14.07 +28 40.1 0.969 0.411 23.8 8.3 429 97 2.00 10 26.89 +28 15.3 0.960 0.441 25.6 8.6 425 99 3.00 10 39.45 +27 44.1 0.953 0.470 27.4 9.0 422 102 4.00 10 51.73 +27 7.1 0.948 0.498 29.2 9.3 417 104 5.00 11 3.71 +26 25.0 0.944 0.526 30.9 9.5 412 106 6.00 11 15.36 +25 38.5 0.942 0.554 32.6 9.8 407 107 7.00 11 26.65 +24 48.0 0.942 0.581 34.3 10.0 401 109 8.00 11 37.59 +23 54.3 0.944 0.607 35.9 10.3 394 110 9.00 11 48.15 +22 57.9 0.947 0.633 37.4 10.5 387 112 10.00 11 58.34 +21 59.3 0.952 0.658 39.0 10.7 379 113 11.00 12 8.15 +20 59.1 0.958 0.683 40.4 10.9 370 114 12.00 12 17.58 +19 57.7 0.966 0.708 41.8 11.1 361 115 WX CETI Albert Jones, Nelson, Nez Zealand reports an outburst of this SU UMa-type dwarf nova on July 8.78UT at mag 12.2. This star, formerly designated as Nova Ceti 1963, is located at: RA 01h14.6m DEC -18 12'(1950) Patrick Schmeer advises us that observations by Taichi Kato in Japan indicate the current outburst is a supermaximum. Guy M Hurst