Electronic Telegram No. 5254
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/1951 G2 = C/1952 C1 (GROENEVELD-PALOMAR)
[Editor's note:  this text replaces that on CBET 5253 (1951 Apr. 7 in table).]
     M. Meyer (Limburg, Germany) and G. W. Kronk (Belleville, IL, USA) report
the identification and linkage of previously unconfirmed comets X/1951 G2 (cf.
IAUC 1437) and X/1952 C1 (cf. IAUC 3246), along with the identification of
additional observations in 1950 and 1951, in the course of the research for 
volume two of their forthcoming *Unconfirmed Comets* book.  X/1951 G2 was 
found by Ingrid Groeneveld on two plates taken on 1951 Apr. 9 with the 10-inch 
Ross-Fecker telescope at McDonald Observatory (similar to the situation with 
C/1951 G1; cf. CBET 5234).  The X/1951 G2 observations were reported in 1954, 
while the X/1952 C1 observations were reported in 1978.  In 2018, Meyer and 
Kronk re-measured these plates and found out that the declination sign given 
on IAUC 1437 was wrong, as was the equinox; their new astrometry (given below)
was published on MPC 110652:

     1951 UT             R.A. (2000) Decl.       Mag.
     Apr.  9.21597   13 09 03.16   - 2 10 10.6   15.5
           9.26597   13 08 57.93   - 2 09 42.3   15.7

X/1952 C1 was found by R. Weinberger during a systematic search of plates of
the first Palomar Observatory Sky Survey; the comet can be seen as a trailed
object in two plates.  In 2012, R. Kracht re-measured the trails and the
observations were published in MPC 77551 (as given below).

     1952 UT             R.A. (2000) Decl.       Mag.
     Feb.  1.42431   11 33 48.39   + 1 23 19.7   17.8
           1.46595   11 33 46.31   + 1 23 32.5   17.5
           1.47292   11 33 45.83   + 1 23 33.5   16.3

At the end of 2022, Meyer tried to find out whether some unconfirmed (X/)
comets might be linkable with each other, finding that these two objects could
be linked with very small residuals; they then identified two plates from
the McDonald Survey of minor planets that were taken on 1951 Apr. 7 (two days
prior to the discovery observation), but unfortunately the sky quality was
not good, resulting in a single plate with a too-bright limiting magnitude
and another inferior plate that showed an uncertain image at the expected
position from the linked orbit.  During the following weeks, Meyer and Kronk
searched numerous plate archives (POSS, Sonneberg, Hamburg, Perth, Goethe
Link, Yerkes, Harvard Sky Patriol, and a few more); either the plates were
not deep enough or the comet was in an area of the plates close to the edge
that were affected by optical coma.  Since the orbit indicated that the comet
(assuming that the link was real) was brightest in 1950 at perhaps magnitude
13-14, they focused on 1950.  The Harvard Sky Patrol images with 3-inch optics
could go as deep as mag 14.5-15 under optimum conditions, but they were often
worse and affected by guiding errors and coma in the outer regions.  Three
plates taken with a 3-inch Ross-Fecker camera were identified from June and
July 1950 that should contain the comet not too close to the edge of the
plates:  June 12 (62-min exposure obtained at Oak Ridge), and July 5 and 16
(60- and 120-min exposures obtained at Boyden Observatory, Bloemfontein,
South Africa).  All three plates show the comet at the expected position
from the linked orbit (which included the additional observation of 1951 Apr.
7); however, due to the small scale of the plates, guiding errors, coma, etc.,
measurements were only made for the mid-point of the exposures (especially the
last plate was very hard to measure due to the ill-defined shape of the
trails).  The uncertainty of the positions is perhaps about +/- 5" (probably a
bit larger in R.A. since the comet was moving mainly in R.A.)

     1950 UT             R.A. (2000) Decl.       Mag.
     June 12.14566   16 31 39.61   - 9 14 28.3   13.2
     July  5.90501   15 38 17.08   - 7 57 53.2   13.5
          16.86187   15 19 54.63   - 7 38 33.0   14

     1951 UT             R.A. (2000) Decl.       Mag.
     Apr.  7.32361   13 12 26.86   - 2 27 33.8   14.4

The following linked orbital elements by S. Nakano (Central Bureau) are from
nine observations spanning 1950 June 12-1952 Feb. 1 (mean residual 1".2), with
corresponding original and future values of 1/a being -0.000241 and +0.000320
(+/- 0.000028) AU**-1, respectively.  The comet passed 0.83 AU from Jupiter on
1949 Aug. 14, 4.37 AU from Saturn on 1951 Oct. 21, and 3.27 AU from Uranus on
1957 Jan. 17 UT.

                    Epoch = 1950 July 18.0 TT
     T = 1950 July 11.93301 TT        Peri. = 108.65837
     e = 1.0002977                    Node  = 354.32048 2000.0
     q = 3.6385241 AU                 Incl. = 170.65367


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

                         (C) Copyright 2023 CBAT
2023 May 10                      (CBET 5254)              Daniel W. E. Green