Electronic Telegram No. 5234 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 G1 (GROENEVELD) An apparent comet discovered via blinking of 10-minute exposures by Ingrid Groeneveld and reported on IAUC 1437 in early 1954 that was found on plates taken by H. Rubingh on a single night (1951 Apr. 2) in the course of a systematic survey of minor planets undertaken at McDonald Observatory with the (loaned) Cook Observatory's 25-cm f/7 Ross-Fecker astrograph during 1950-1951 (cf. Groeneveld and Kuiper 1954, Ap.J. 120, 200) has been now identified by M. Meyer, G. W. Kronk, and W. H. Osborn on plates taken on additional nights in 1951 as part of Meyer's and Kronk's work to find observations of old, unconfirmed comets for a forthcoming book. (Groeneveld was at Yerkes from November 1952 until May 1954.) In 2018, Meyer re-measured the discovery plates for what was then designated X/1951 G1 (cf. Marsden and Williams 1996, *Catalogue of Cometary Orbits 1996*, p. 110), and he deduced that the original observations measured by G. Van Biesbroeck were for equinox 1900.0 and not for equinox 1950.0 as erroneously stated on IAUC 1437 -- where the comet was said to be of mag 15 with a nuclear condensation 8" in diameter with a faint coma extending 40" (presumably) to the northwest (those descriptive comments surely coming from Van Biesbroeck). Meyer's re-measured astrometry for the discovery of X/1951 G1 as they appeared on MPC 110652 are tabulated below. 1951 UT R.A. (2000) Decl. Mag. Observer Apr. 2.17361 12 07 37.90 +13 19 52.5 15.3 Rubingh 2.22292 12 07 36.28 +13 19 49.4 14.9 " Osborn has pulled out additional plates at Yerkes Observatory in collaboration with Meyer and Kronk, which extend the arc to just over one week in 1951, which were also made with the 25-cm f/7 Ross-Fecker astrograph (which itself was on loan then to McDonald from the University of Pennsylvania's Cook Observatory). The plates were 8 x 10 inches in size, corresponding to a field size of 6.5 x 8.1 degrees, and were taken in pairs separated by about 1 hour (Kuiper et al. 1958, Ap.J. Suppl. 3, 289). Meyer measured tabulated astrometry below using UCAC-4 reference stars, and he describes the comet as diffuse with condensation with a coma diameter of about 10" with an extension up to 40" long toward p.a. 290-340 degrees. 1951 UT R.A. (2000) Decl. Mag. Observer Mar. 31.24444 12 08 38.57 +13 21 29.6 14.3 Rubingh Apr. 1.25069 12 08 06.82 +13 20 41.8 14.4 " 1.29167 12 08 05.40 +13 20 40.1 14.6 " 2.26250 12 07 34.97 +13 19 46.3 14.0 " 3.30556 12 07 02.29 +13 18 40.9 14.5 " 4.26181 12 06 32.83 +13 17 38.4 14.5 " 7.30208 12 05 00.24 +13 13 35.7 15.0 " Meyer adds that they have checked other plate archives, as well, to no avail. An ephemeris based on the seven-day-arc parabolic orbit suggests that the same survey may have detected the comet on plates taken on 1952 May 25 and 26, when it might have been as bright as in 1951, but a thorough checking of those plates revealed no certain trace. Meyer obtained the following parabolic orbital elements from nine observations spanning 1951 Mar. 31-Apr. 7 (mean residual 0".8): T = 1951 Nov. 7.0269 TT Peri. = 187.5385 Node = 31.5051 2000.0 q = 3.64576 AU Incl. = 18.6652 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 March 16 (CBET 5234) Daniel W. E. Green