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IAUC 2927: 1975n

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                                                  Circular No. 2927
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.

COMET WEST (1975n)
     Further observations have been reported of a secondary nucleus,
and since Mar. 11 observers have described as many as four discrete
condensations.  Although it is difficult to correlate all the data
given on IAUC 2924, J. Bortle, Brooks Observatory, who denotes by A
and B the primary and secondary nuclei he observed on Mar. 8, was
able to identify these same nuclei on Mar. 12, at which time he
also noted nucleus C up the gas tail from A and nucleus D farthest
to the east.  The trapezoidal configuration on Mar. 12 was independently
reported by S. O'Meara, Harvard College Observatory; by P.
MacKinnon, D. Somers, D. Welch, R. Dick and F. Lossing, North
Mountain Observatory, near Ottawa; and photographically by S. Murrell
and C. Knuckles, New Mexico State University (61-cm f/40 reflector,
plates measured by E. J. Reese).  Although J. S. Neff, D. A.
Ketelsen and V. V. Smith, University of Iowa, had described three
of the nuclei (evidently A, B and D) as of equal brightness and
essentially collinear on Mar. 11, G. H. Herbig, D. Duncan and D.
Soderblom, observing with the 305-cm reflector at the Lick Observatory
on Mar. 13 and 14, indicated that the basic configuration of
Mar. 12 had been maintained.  Observations of separation, position
angle and magnitude difference (all with respect to A) follow:

Nucleus B.  Mar. 6.46 UT, (10"), 5o, 0 (F. Pilcher, Jacksonville,
   Illinois); 8.53, 3".5, (13o), 0 (Murrell et al.); 10.46, -, ~ 0o
   - (P. Maley, Houston, Texas); 10.86, (10") 135o [315o?], 0.5
   (K. Ikeya, Japan); 11.5, (30"), 345o-350o, 0 (Neff et al.); 12.4,
   4"-5", 345o, 1.3 (Bortle); 12.50, 8".2, 337o, > 0 (Murrell et
   al.); 13.5, 12", 330o, 2 (Herbig et al.); 14.4, 8", 330o, 2
   (Bortle); 14.5, 12", 330o, 2 (Herbig et al.).

Nucleus C.  Mar. 11.5 UT, (5"), 280o, 2 (Neff et al.); 12.4, 2",
   295o, 1 (Bortle); 12.50, 2".6, 294o, 0 (Murrell et al.); 13.5,
   4"-5", 300o, 0 (Herbig et al.); 14.4, not observed, not observed,
   > 3 (Bortle); 14.5, 4"-5", 300o, 3 (Herbig et al.).

Nucleus D.  Mar. 11.5 UT, (15"), 345o-350o, 0 (Neff et al.); 12.4,
   2", 15o, ~ 2 (Bortle); 12.50, 4", 0o, > 0 (Murrell et al.); 13.5,
   5", 340o, 2 (Herbig et al.); 14.4, 3", 345o, 2.5-3.0 (Bortle);
   14.5, 5", 340o, 2 (Herbig et al.).

     Herbig et al. remark that the nuclear condensations show
continuous spectra (over 4500-8500 A).  The coma spectrum also shows
the usual emissions, including possibly H-alpha on the shortward fringe
of solar-absorption H-alpha.  The tail spectrum includes H2O+.

1976 March 15                  (2927)              Brian G. Marsden

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