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Comet 100P/HARTLEY   = 1985 L1 = 1991 E1

100P on Cometography

Data obtained by use of  FOCAS-II software

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

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

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

100P          20/04/2022 22:31:42  18.66  18.11  17.87                        3.6  18.2  B96

100P          20/04/2022 22:31:42*  0.19   0.16   0.02                          2   3.4  Gai

100P          27/04/2022 22:49:02  18.64  18.41  18.05  17.68  17.73          4.2  18.1  B96

100P          27/04/2022 22:49:02*  0.17   0.50   0.62   0.66   0.91            2   3.1  Gai

                                                                     AFRHO         LOG

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

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

100P          20/04/2022 22:31:42    1.48   2.19  18.58  18.20    4      5     1  0.728  B96

100P          27/04/2022 22:49:02    1.52   2.17  18.14  18.33    4      5     1  0.687  B96

Discovery:

Malcolm Hartley (U.K. Schmidt Telescope Unit, Australia) discovered this comet on a pair of plates exposed with a 1.2-m Schmidt on 1985 June 13.38 and June 13.48. He estimated the magnitude as 16 and said there was a prominent tail extending over one arc minute toward the southeast.

Recovery:

The comet might have become lost if it was not for the accidental recovery by Carolyn and Eugene Shoemaker and David Levy in 1991. Using the 0.46-m Schmidt at Palomar Observatory, the team announced the discovery of a comet on a pair of plates exposed on 1991 March 12. They described it as magnitude 16.5, diffuse and condensed, with a tail extending over one arc minute. Brian G. Marsden (Harvard-Smithsonian Center for Astrophysics) noted the comet was about 16 degrees from the prediction for periodic comet Hartley 1 and was moving similar to what would be expected for that comet. He then computed an orbit that successfully linked the 1985 and 1991 positions, noting that Hartley 1 had passed 0.36 AU from Jupiter during 1988 February. Marsden showed that the comet's perihelion date in 1991 was May 17.68.