[Iaude] CBET 4803: COMET C/2020 F3

quai at eps.harvard.edu quai at eps.harvard.edu
Sat Jun 27 20:00:43 EDT 2020


                                                  Electronic Telegram No. 4803
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2020 F3 (NEOWISE)
     This comet (cf. CBETs 4740, 4753) is now exiting the SOHO spacecraft's
LASCO C3 imaging camera after having been visible the last three days.  It
has exhibited what appears to be a dust tail that is quite bright for the
first 17' or so, extending faintly out to perhaps 45' or more.  C. S.
Morris, Fillmore, CA, USA, writes that he has analyzed FITS images posted at
website URL https://umbra.nascom.nasa.gov/pub/lasco/lastimage/level_05/.
Using the differential photometry feature in "Maxim DL" software and a
measurement aperture radius of 5 pixels on the SOHO C3 FITS images, the
following total magnitudes for the comet's coma (excluding tail as much as
possible) were obtained by Morris when measured against gamma Gem (assumed
magnitude V = 1.9):   June 27.08 UT, 2.0; June 27.7, 1.7.  Given the problems
with large pixel size (about 1' per pixel) and bandpass for the SOHO camera
(its clear filter has a broad bandpass spanning 400-850 nm), and the bright
inner tail, these results are intended to show the approximate total
brightness of the comet rather than anything precise.
     Additional selected visual total-magnitude and coma-diameter estimates
(cf. CBET 4770):  Apr. 27.45 UT, 10.0, 4' (P. Camilleri, Katherine, NT,
Australia, 0.40-m reflector); May 8.44, 10.0, 3' (Camilleri); 10.37, 9.9,
4'.6 (C. Wyatt, Walcha, NSW, Australia, 25-cm reflector); 11.45, 10.3, 2' (A.
Pearce, Nedlands, W. Austraiia, 0.25-m reflector); 14.90, 9.6, 2' (A. Amorim,
Florianopolis, Brazil, 0.09-m refractor); 16.93, 9.5, 3' (M. Goiato,
Aracatuba, 0.22-m reflector; near a star of mag 10.5); 18.42, 8.7, 6'
(Camilleri, 0.08-m refractor); 23.91, 8.6, 3' (Amorim); 26.91, 8.3, -- (J. G.
de S. Aguiar, Campinas, Brazil, 25x100 binoculars); 27.81, 7.6, 8' (S. J.
O'Meara, Maun, Botswana, 8x42 binoculars); 28.92, 7.7, 8' (Goiato, 7x50
binoculars; moonlight); 30.41, 7.9, 4' (Camilleri, 20x80 binoculars); 30.92,
7.3, 8' (Goiato, 20x100 binoculars; moonlight).
     H. Sato, Tokyo, Japan, writes that CCD images taken remotely with a
0.51-m astrograph at Siding Spring, NSW, show a strongly condensed comet with
an outer coma 5'.2 in diameter; the integrated magnitude was 10.6 as measured
within a circular aperture of radius 157".7.
     New astrometry of this comet that have been archived by the Minor Planet
Center (see website URL https://minorplanetcenter.net/db_search) have been
used to produce the following updated orbital elements by S. Nakano, Sumoto,
Japan, which are from 332 observations spanning Mar. 27-May 29 (mean residual
0".5).  The corresponding original and future values of 1/a are +0.003640
and +0.002744, respectively.  The comet's closest approach to earth will
occur on 2020 July 23 UT at 0.69.

                    Epoch = 2020 July 10.0 TT
     T = 2020 July  3.68150 TT        Peri. =  37.27404
     e = 0.9991878                    Node  =  61.01074 2000.0
     q = 0.2947079 AU                 Incl. = 128.93729

The following ephemeris extension to CBET 4770 by the undersigned (from the
above orbital elements) uses photometric power-law parameters H = 7.0 and
2.5n = 12.5, which represents magnitude estimates given above generally,
but for heliocentric distances 1.6 AU < r only, so caution is advised,
especially because values of n closer to 3 are much more typical of
long-period comets.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2020 06 20    05 58.32   +12 58.0    1.467    0.503    10.5    21.6   4.1
2020 06 21    05 57.86   +13 56.7    1.454    0.481     9.5    20.4   3.8
2020 06 22    05 57.38   +14 57.5    1.439    0.460     8.6    19.3   3.6
2020 06 23    05 56.90   +16 00.6    1.423    0.439     7.8    18.4   3.3
2020 06 24    05 56.43   +17 06.2    1.406    0.418     7.2    17.9   3.0
2020 06 25    05 55.99   +18 14.6    1.388    0.398     6.9    17.9   2.7
2020 06 26    05 55.58   +19 25.8    1.368    0.379     6.9    18.8   2.4
2020 06 27    05 55.25   +20 40.2    1.346    0.361     7.2    20.7   2.1
2020 06 28    05 55.04   +21 57.9    1.323    0.344     7.8    23.6   1.8
2020 06 29    05 55.00   +23 19.0    1.297    0.329     8.6    27.5   1.5
2020 06 30    05 55.19   +24 43.5    1.270    0.317     9.6    32.3   1.3
2020 07 01    05 55.71   +26 11.3    1.241    0.307    10.7    37.9   1.1
2020 07 02    05 56.66   +27 42.1    1.210    0.299    11.8    44.1   0.9
2020 07 03    05 58.16   +29 15.4    1.177    0.295    13.0    50.8   0.7
2020 07 04    06 00.33   +30 50.8    1.143    0.295    14.2    57.7   0.7
2020 07 05    06 03.30   +32 27.5    1.108    0.298    15.3    64.7   0.6
2020 07 06    06 07.20   +34 04.8    1.072    0.304    16.4    71.4   0.7
2020 07 07    06 12.15   +35 41.9    1.036    0.313    17.5    77.8   0.8
2020 07 08    06 18.26   +37 18.1    1.000    0.324    18.5    83.7   0.9
2020 07 09    06 25.63   +38 52.5    0.965    0.338    19.4    89.0   1.0
2020 07 10    06 34.38   +40 24.3    0.931    0.354    20.3    93.6   1.2
2020 07 11    06 44.59   +41 52.4    0.898    0.372    21.2    97.6   1.4
2020 07 12    06 56.35   +43 15.6    0.867    0.390    22.2   101.0   1.6
2020 07 13    07 09.73   +44 32.4    0.838    0.410    23.1   103.6   1.8
2020 07 14    07 24.78   +45 41.0    0.812    0.431    24.1   105.7   2.0
2020 07 15    07 41.47   +46 39.3    0.787    0.452    25.1   107.1   2.2
2020 07 16    07 59.74   +47 25.3    0.765    0.473    26.3   107.9   2.4
2020 07 17    08 19.41   +47 56.6    0.746    0.495    27.6   108.2   2.5
2020 07 18    08 40.20   +48 11.1    0.730    0.517    29.0   107.9   2.7
2020 07 19    09 01.77   +48 07.3    0.716    0.540    30.5   107.2   2.9
2020 07 20    09 23.66   +47 44.4    0.706    0.562    32.1   106.0   3.1
2020 07 21    09 45.44   +47 02.3    0.698    0.584    33.8   104.5   3.3
2020 07 22    10 06.66   +46 01.9    0.693    0.607    35.6   102.6   3.5
2020 07 23    10 26.98   +44 44.9    0.692    0.629    37.5   100.4   3.7
2020 07 24    10 46.12   +43 13.8    0.693    0.651    39.4    98.1   3.9
2020 07 25    11 03.93   +41 31.2    0.697    0.674    41.3    95.6   4.1
2020 07 26    11 20.33   +39 40.1    0.704    0.696    43.2    93.0   4.3
2020 07 27    11 35.35   +37 43.1    0.713    0.718    45.0    90.4   4.5
2020 07 28    11 49.02   +35 42.9    0.725    0.740    46.7    87.7   4.7
2020 07 29    12 01.44   +33 41.5    0.739    0.762    48.4    85.1   4.9
2020 07 30    12 12.71   +31 40.6    0.755    0.783    49.9    82.5   5.1
2020 07 31    12 22.95   +29 41.7    0.773    0.805    51.4    80.0   5.3
2020 08 01    12 32.25   +27 45.9    0.793    0.827    52.7    77.6   5.5
2020 08 02    12 40.72   +25 53.8    0.814    0.848    53.9    75.2   5.7
2020 08 03    12 48.45   +24 06.0    0.837    0.869    55.0    73.0   5.9
2020 08 04    12 55.52   +22 22.8    0.860    0.890    56.0    70.8   6.0
2020 08 05    13 02.02   +20 44.2    0.885    0.911    56.8    68.7   6.2
2020 08 06    13 08.00   +19 10.4    0.911    0.932    57.6    66.8   6.4
2020 08 07    13 13.52   +17 41.2    0.938    0.953    58.3    64.9   6.6
2020 08 08    13 18.63   +16 16.6    0.965    0.974    58.9    63.1   6.8
2020 08 09    13 23.39   +14 56.3    0.994    0.994    59.4    61.3   7.0
2020 08 10    13 27.82   +13 40.1    1.022    1.014    59.8    59.7   7.1
2020 08 11    13 31.96   +12 27.9    1.052    1.035    60.1    58.1   7.3
2020 08 12    13 35.84   +11 19.3    1.081    1.055    60.4    56.6   7.5
2020 08 13    13 39.50   +10 14.3    1.112    1.075    60.6    55.2   7.6
2020 08 14    13 42.94   +09 12.6    1.142    1.095    60.7    53.8   7.8
2020 08 15    13 46.19   +08 14.0    1.173    1.115    60.8    52.5   7.9
2020 08 16    13 49.28   +07 18.2    1.204    1.134    60.8    51.2   8.1
2020 08 17    13 52.21   +06 25.2    1.235    1.154    60.8    50.0   8.2
2020 08 18    13 55.00   +05 34.6    1.267    1.173    60.8    48.8   8.4
2020 08 19    13 57.66   +04 46.5    1.298    1.193    60.7    47.7   8.5

2020 08 24    14 09.43   +01 16.0    1.458    1.288    59.7    42.6   9.2
2020 08 29    14 19.28   -01 34.4    1.618    1.381    58.0    38.3   9.8
2020 09 03    14 27.85   -03 55.5    1.778    1.471    55.9    34.6  10.3
2020 09 08    14 35.52   -05 54.7    1.935    1.560    53.4    31.2  10.8
2020 09 13    14 42.56   -07 37.3    2.089    1.647    50.7    28.2  11.3
2020 09 18    14 49.12   -09 06.9    2.239    1.732    47.7    25.4  11.7
2020 09 23    14 55.34   -10 26.1    2.386    1.815    44.7    22.9  12.1
2020 09 28    15 01.28   -11 37.0    2.528    1.897    41.5    20.5  12.5


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

                         (C) Copyright 2020 CBAT
2020 June 27                     (CBET 4803)              Daniel W. E. Green



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