Electronic Telegram No. 5249
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
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Prepared using the Tamkin Foundation Computer Network


COMET C/2020 H11 (PANSTARRS-LEMMON)
    The Minor Planet Center has reported that D. Rankin, D. Bamberger, and B.
Gray found a linkage of five separate single-night observations located in the
Minor Planet Center's online "isolated tracklet file" (ITF) spanning 2020 Apr.
21-May 20, which revealed a near-parabolic orbit; a very condensed 5" coma and
a straight 11" tail was found in Mt. Lemmon Survey images obtained on 2020 May
15 with the 1.5-m reflector.  After the object was posted on the MPC's PCCP
webpage, pre-discovery positions were identified by R. Weryk (Department of
Physics and Astronomy, University of Western Ontario) in images obtained with
the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on 2019 June 2,
7, 10, and 29 (at mag 21.8-22.6) and on 2019 July 24 (mag 21.8-23.5), as well
as on 2020 Mar. 23 (mag 22.0-22.2) and 2020 Apr. 19 (mag 21.5) on images
obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala.
Weryk notes that four 45-s w-band survey images taken on 2020 Apr. 21.6 UT
show a condensed coma of size 1".6 (full-width-at-half-maximum) in 1".2 seeing
with a possible short tail to the southeast.  He adds that four similar
images taken on 2020 Apr. 27.52-27.56 show a condensed coma of size 1".6
(FWHM) in 1".2 seeing, also with a possible short tail to the southeast.  And
four similar images taken on 2020 May 17.33-17.36 show a condensed coma of
size 1".8 (FWHM) in 1".4 seeing, also with a possible short tail toward the
southeast.  The discovery observations are tabulated below.

     2020 UT             R.A. (2000) Decl.       Mag.
     Apr. 21.57079   15 24 23.96   +14 43 26.6   22.1
          21.58175   15 24 23.44   +14 43 29.9   22.3
          21.59266   15 24 22.89   +14 43 33.4   22.1
          21.60355   15 24 22.37   +14 43 37.2   22.2
          27.52191   15 19 30.13   +15 13 06.9   21.8
          27.53373   15 19 29.52   +15 13 10.0   22.0
          27.55735   15 19 28.34   +15 13 16.7   21.8
     May  15.31358   15 04 19.59   +16 23 53.4   21.2
          15.31833   15 04 19.32   +16 23 55.2   21.1
          15.32307   15 04 19.04   +16 23 56.3   21.5
          15.32783   15 04 18.87   +16 23 56.7   21.7

A single night of pre-discovery observations made with the Pan-STARRS1
reflector from 2019 June 9.44-9.48 UT (when the comet was at mag 22.3-22.6)
was also found in the ITF.  The astrometry appears on MPEC 2023-H237.
     The following orbital elements by S. Nakano (Central Burea7) are from
53 observations spanning 2019 June 2-2021 May 8 (mean residual 0".3), with
corresponding original and future values of 1/a being +0.000213 and
+0.000316 (+/- 0.000002) AU**-1, respectively.  The comet passed 2.60 AU
from Saturn on 2017 Nov. 9 and 4.05 AU from Jupiter on 2019 Mar. 4 UT.

                    Epoch = 2020 Sept. 28.0 TT
     T = 2020 Sept. 15.67036 TT       Peri. =  91.50043
     e = 1.0000207                    Node  = 303.00339 2000.0
     q = 7.6310690 AU                 Incl. = 151.41469


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2023 CBAT
2023 April 28                    (CBET 5249)              Daniel W. E. Green