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IAUC 2924: 1976d; 1976c; 1975n

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                                                  Circular No. 2924
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.

     M. P. Candy, Perth Observatory, provides the following orbital
elements and ephemeris, based on three accurate observations
covering a 3-day arc; residuals are in excess of 5".

       T = 1976 Feb. 25.099 ET   Peri. = 221.62
                                 Node  =  69.24   1950.0
       q = 0.6785 AU             Incl. = 147.67

     1976 ET     R. A. (1950) Decl.     Delta     r      m1
     Mar.  8    23 06.4     -50 37      0.558   0.722    8.8
           9    23 34.5     -50 36
          10     0 03.4     -50 05
          11     0 32.0     -49 05
          12     0 59.6     -47 36
          13     1 25.4     -45 42
          14     1 48.9     -43 29      0.537   0.773    9.1

Magnitudes have been added, calculated from m1 = 11.5 + 5 log Delta +
10 log r.

     E. Roemer, Lunar and Planetary Laboratory, provides the
following semiaccurate position, obtained with the 154-cm reflector.
The magnitude is provisional; trace of tail north-northeastward.

     1976 UT          R. A. (1950) Decl.      m2
     Mar.  5.32500   10 51.48    -42 48.8    16-17

COMET WEST (1975n)
     S. D. Sinvhal, Uttar Pradesh State Observatory, reports that
observations by G. Babu on Mar. 6.00 UT showed very strong Na
emission, strong Swan bands and detectable CN 3883 A and 4214 A and C3
4050 A; on Mar. 7.00 all emissions except the Swan bands had considerably
weakened.  D. A. Ketelsen and J. S. Neff, University of Iowa,
report that observations of the nuclear region (resolution 16 A) on
Mar. 7.5 showed a strong continuum, strong emission features due to
CN and C2 and rather weaker emissions due to Na and C3.

     J. Young, Table Mountain Observatory, reports the following
visual tail lengths: Mar. 2.58 UT, > 10o; 6.54, 25o; 7.55; 28o;
8.55, 30o.  J. Bortle, Brooks Observatory, reports the following
observations of tail structure: Mar. 7.41 UT, 5o.5 long in p.a. 295o
(a pair of gas tails); 8o.5 in 305o and 11o.5 in 310o and 19o in 330o
(dust); 8.40, 8o.5 in 298o (gas), 11o in 307o and 16o in 310o and
25o in 320o (dust).  Corrigendum: on IAUC 2919, the p.a. for the
Feb. 29.47 observation should read 340o.

     Z. Sekanina, Center for Astrophysics, comments on photographic
observations of the tail: "On photographs (4.5-cm f/4 camera, Royal
Pan emulsion) taken on Mar. 5.51 and 6.50 UT J. A. Farrell, Los
Alamos, New Mexico, noted a broad, dust tail composed of a number
of 'synchronic bands', similar to those observed in comet 1957 V;
the breadth of the tail had increased by the latter date, while the
bands showed a systematic translational motion of about 1o.6 per day
and rotated at about 13o per day relative to the faint plasma tail;
Farrell also detected two streamers superimposed on the dust tail,
one of them essentially coinciding with its southern border.  On a
print (f = 135 mm camera, IIIa-J emulsion) obtained on Mar. 5.50 UT
by D. Willmarth, Mount Hopkins Observatory, I find the main body of
the tail to be between p.a. 310o and 357o, but a fainter glow can
also be detected in the north-northeast, apparently terminating in
p.a. 40o; the bright section of the dust tail consists of as many
as 20 'synchronic bands', those nearest the nucleus being directed
toward p.a. 320o, the farthest ones toward p.a. 330o; the most
distant bands reach to at least 19o from the nucleus, but traces of
the dust tail extend out to some 25o.  This bright section of the
dust tail consists of postperihelion particle emissions, while the
faint northeast section, which can be followed for a few degrees,
is made up of somewhat heavier particles emitted during the week
before perihelion.  Willmarth's print also shows a plasma tail > 15o
long in the form of a 15o sector centered on p.a. 300o."

     D. Elmore and S. Koutchmy, Sacramento Peak Observatory, report
that daylight photographic measurements on Feb. 26.81 UT at an
effective wavelength of 8750 A (passband 800 A) give an integrated
magnitude of -3.65 +/- 0.40 (30' field).  Selected recent total visual
magnitude estimates: Mar. 2.56 UT, 0 (M. J. Mayo and J. Truxton,
Agoura, California, 7 x 50 binoculars); 3.23, 0 to -0.5 (B.
Apeldoorn et al., Hoeven, The Netherlands, naked eye); 4.2, 0 (C.
Cosmovici, Lecce, Italy, naked eye); 5.55, < 1.0 (Mayo and Truxton);
6.56, 1.2 (Mayo and Truxton); 7.41, 1.3 (Bortle, 10 x 50 binoculars);
7.56, 1.4 (Mayo and Truxton); 8.40, 1.8 (Bortle).

     Visual observations of secondary nuclei: Mar. 5.23 UT, separation
3", p.a. 50o, magnitude difference 0.5 (E. H. Geyer and M.
Hoffmann, Hoher List Observatory, 36-cm refractor, 250 x); 7.46, -,
120o, 0 (R. Boyd, Miami, Florida, 20-cm reflector, 210 x); 7.55, 4"
1 (Young, 61-cm reflector, 500 x); 8.40, < 5", 340o, 1 (Bortle,
32-cm reflector, 100 x); 8.42, 1".5, 350o, 0.5 (S. O'Meara, Harvard
Observatory, 23-cm refractor, 300 x); 8.55, 2", -, - (Young).

1976 March 9                   (2924)              Brian G. Marsden

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