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78P/Gehrels - (= 1973 S1  = P/1981 L1)

78P on W. KRONK’s Cometograpy

Data obtained by use of  FOCAS-II software

                                   10x10  20x20  30x30  40x40  50x50  60x60   SNR   SB   COD

OBJECT        DATE       TIME        +/-    +/-    +/-    +/-    +/-    +/-     N  FWHM  CAT

------------  ---------- --------  -----  -----  -----  -----  -----  -----  ----  ----  ---

78P           17/02/2013 23:29:53  17.39  16.72  16.35  16.14  15.87  15.78   2.2  16.9  B96

78P           17/02/2013 23:29:53*  0.14   0.22   0.25   0.40   0.41   0.57     3   3.9  CMC

78P           05/03/2013 00:09:15  17.75  17.28  17.14  17.23                 3.8  17.3  B96

78P           05/03/2013 00:09:15*  0.08   0.08   0.19   0.30                   5   3.4  CMC

78P           24/07/2018 00:03:56  16.64  16.21  15.92  15.93  15.97          9.9  16.7  B96

78P           24/07/2018 00:03:56*  0.05   0.12   0.16   0.17   0.21            5   3.7  USN

78P           03/08/2018 00:45:38  15.95  15.45  15.23  15.15  15.13  15.14   8.7  16.9  B96

78P           03/08/2018 00:45:38*  0.04   0.04   0.07   0.10   0.09   0.11     4   4.0  CMC

78P           04/08/2018 00:56:51  15.92  15.18  14.81  14.58  14.45  14.41   5.3  16.3  B96

78P           04/08/2018 00:56:51*  0.10   0.18   0.23   0.31   0.40   0.54     3   3.8  CMC

78P           06/08/2018 00:51:57  15.91  15.39  15.17  15.06  14.99  14.97  17.0  18.0  B96

78P           06/08/2018 00:51:57*  0.02   0.05   0.06   0.09   0.10   0.12     4   3.9  CMC

78P           06/08/2018 23:49:58  15.92  15.41  15.16  15.02  14.99  14.94  13.7  17.5  B96

78P           06/08/2018 23:49:58*  0.02   0.02   0.04   0.02   0.03   0.05     3   3.8  CMC

78P           01/09/2018 20:45:07  15.59  15.03  14.77  14.65  14.56  14.51  20.4  16.9  B96

78P           01/09/2018 20:45:07*  0.00   0.02   0.02   0.01   0.05   0.07     2   3.8  CMC

78P           01/09/2018 20:45:07  15.59  15.03  14.77  14.65  14.56  14.51  20.4  16.9  B96

78P           01/09/2018 20:45:07*  0.00   0.02   0.02   0.01   0.05   0.07     2   3.8  CMC

78P           02/09/2018 20:41:08  15.58  15.03  14.72  14.58  14.50  14.44  20.1  17.0  B96

78P           02/09/2018 20:41:08*  0.04   0.04   0.06   0.05   0.06   0.04     4   3.8  CMC

78P           24/09/2018 20:17:58  15.34  14.71  14.50  14.35  14.23  14.13   6.5  16.4  B96

78P           24/09/2018 20:17:58*  0.03   0.03   0.04   0.05   0.09   0.16     4   3.9  CMC

78P           10/10/2018 19:01:43  15.65  15.03  14.74  14.53  14.39  14.30  17.4  17.0  B96

78P           10/10/2018 19:01:43*  0.01   0.04   0.04   0.04   0.05   0.04     3   3.8  CMC

78P           15/10/2018 18:47:44  15.74  15.14  14.85  14.66  14.54  14.47  14.9  16.6  B96

78P           15/10/2018 18:47:44*  0.01   0.03   0.10   0.15   0.20   0.23     3   3.8  CMC

78P           16/10/2018 19:31:27  15.71  15.16  14.85  14.70  14.59  14.59  14.6  16.9  B96

78P           16/10/2018 19:31:27*  0.01   0.04   0.02   0.03   0.02   0.07     2   3.9  CMC

78P           04/11/2018 19:24:08  15.74  15.18  14.84  14.66  14.52  14.50  12.5  16.7  B96

78P           04/11/2018 19:24:08*  0.06   0.06   0.02   0.04   0.01   0.06     3   3.9  CMC

78P           21/03/2020 20:16:20  17.70  16.96  16.49  16.17  16.09  16.03   6.1  18.0  B96

78P           21/03/2020 20:16:20*  0.16   0.07   0.04   0.06   0.04   0.03     3   3.7  Gai

78P           22/03/2020 20:22:48  17.87  17.19  16.88  16.87  16.89          7.3  18.2  B96

78P           22/03/2020 20:22:48*  0.02   0.07   0.15   0.14   0.02            2   3.6  Gai

78P           23/03/2020 20:31:15  17.82  17.12  16.79  16.66  16.71  16.79   9.1  18.1  B96

78P           23/03/2020 20:31:15*  0.01   0.06   0.04   0.02   0.09   0.04     3   3.5  Gai

78P           24/03/2020 20:27:24  17.72  17.16  16.96  16.88                 8.2  18.1  B96

78P           24/03/2020 20:27:24*  0.06   0.13   0.10   0.05                   3   3.8  Gai

                                                                     AFRHO         LOG

COMET         UTC                   DELTA    r    BOX "   MAG   RSR    CM    +/-  AFRHO  OBS

------------  -------------------   -----  -----  -----  -----  ---  -----  ----  -----  ---

78P           24/07/2018 00:03:56    1.87   2.79  14.76  16.39   10     72     7  1.860  B96

78P           03/08/2018 00:45:38    1.77   2.74  15.58  15.64    9    125    14  2.097  B96

78P           04/08/2018 00:56:51    1.76   2.74  15.66  15.45    5    147    28  2.168  B96

78P           06/08/2018 00:51:57    1.74   2.73  15.80  15.59   17    127     7  2.103  B96

78P           06/08/2018 23:49:58    1.74   2.72  15.87  15.59   14    125     9  2.096  B96

78P           01/09/2018 20:45:07    1.63   2.61  16.95  15.20   20    144     7  2.159  B96

78P           01/09/2018 20:45:07    1.63   2.61  16.95  15.20   20    144     7  2.159  B96

78P           02/09/2018 20:41:08    1.63   2.60  16.96  15.17   20    146     7  2.166  B96

78P           24/09/2018 20:17:58    1.67   2.51  16.54  14.93    7    178    27  2.251  B96

78P           10/10/2018 19:01:43    1.75   2.44  15.73  15.26   17    138     8  2.141  B96

78P           15/10/2018 18:47:44    1.79   2.42  15.43  15.37   15    127     9  2.104  B96

78P           16/10/2018 19:31:27    1.79   2.41  15.36  15.37   15    129     9  2.110  B96

78P           04/11/2018 19:24:08    1.94   2.34  14.19  15.44   13    132    11  2.121  B96

78P           21/03/2020 20:16:20    2.52   3.25  10.93  17.55    6     62    10  1.790  B96

78P           22/03/2020 20:22:48    2.54   3.26  10.86  17.70    7     55     8  1.739  B96

78P           23/03/2020 20:31:15    2.55   3.26  10.80  17.60    9     61     7  1.783  B96

78P           24/03/2020 20:27:24    2.57   3.27  10.73  17.63    8     60     7  1.780  B96

Tom Gehrels (Lunar and Planetary Laboratory, Arizona, USA) discovered this comet while examining plates exposed with Palomar Observatory's 122-cm Schmidt Telescope during a minor planet survey. The comet's diffuse image was noted on plates exposed on 1973 September 29, September 30, October 4, and October 5. The brightness was estimated as 15-16, while a fan-shaped tail extended about two arc minutes.  This comet was assigned as 1973 S1 (GEHRELS) (new-style format)

The comet was officially announced on October 31, at which time B. G. Marsden (Central Bureau for Astronomical Telegrams) provided both a parabolic and elliptical orbit. The latter indicated an orbital period of 8.76 years. This orbit allowed numerous immediate observations, and the short-period nature of the orbit was confirmed on November 7 when Marsden issued a more precise orbit indicating a perihelion date of 1973 November 30 and an orbital period of 7.93 years. This orbit indicated the comet had passed 0.9 AU from Jupiter in 1971, and that prior to that encounter the orbital period had been 8.5 years.

Recovery: W. and A. Cochran (McDonald Observatory, Texas, USA) recovered this comet on 1981 June 8. The brightness was then estimated as 19.5 and the position indicated Marsden's prediction was only 0.15 day off. The maximum brightness of the 1981 return never exceeded 16. The comet was closest to Earth (1.3738 AU) on October 26.

Info discoverer: Anton M.J. (Tom) Gehrels (Haarlemmermeer, 21 February 1925 - Tucson, 11 July 2011) was an American astronomer of Dutch origin. Together with Kees van Houten and his wife Ingrid van Houten-Groeneveld, he discovered thousands of asteroids and comets. He has also written many books and set up the Spacewatch project together with the American astronomer Bob McMillan. In 2007 he received the Masursky Award. Gehrels taught once a year in India where he was attached to the Physical Research Laboratory in Ahmedabad.

Last updated : 2020-10-20