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                                                  Circular No. 3408
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758

     Rolf Meier, Ottawa, Ontario, reports the discovery of a comet
(40-cm f/5 reflector, 56 x).  Available observations follow:

     1979 UT          R. A. (1950) Decl.     m1     Observer
     Sept.20.06250   13 34.5     +68 38     11.5    Meier
          20.21128   13 34.7     +68 38     13.5    Giclas
          21.16119   13 32.2     +68 13     12      Bulger

R. Meier (Ottawa, Ontario).  Object diffuse with condensation.
H. L. Giclas (Lowell Observatory).  Very diffuse and uncondensed.
J. H. Bulger and C.-Y. Shao (Harvard College Observatory).  40-cm
   astrograph.  Diffuse with condensation, possible tail.

     At its recent meetings in Montreal, IAU Commission 20 resolved
that geometric ephemerides should be abandoned and that all future
ephemerides of minor planets, comets and satellites should be
either astrometric or apparent.  In practice, this means that ephemerides
published on these Circulars will be astrometric, geocentric
and referred to the standard equinox 1950.0.  An astrometric
ephemeris is one in which the light-time correction has been applied,
so that the ephemeris is directly comparable with star positions
given in a catalogue referred to equinox 1950.0, except for the
application of observer-dependent effects, such as parallax,
refraction and diurnal aberration; an astrometric position differs from
an apparent position by the effects of precession, nutation and
annual aberration.  Unless otherwise stated, the positions tabulated
are those corresponding to 0 hours Ephemeris Time (which is now
50 seconds fast on Universal Time).  The difference between an
astrometric ephemeris and a geometric ephemeris of the type published
hitherto rarely exceeds 0'.5.

     S. S. Mims, James-Mims Observatory, points out that there exists
the possibility of a meteor shower around Oct. 9.36 UT when
the earth passes within 0.0017 AU of the orbit of P/Giacobini-Zinner,
which will have passed the point 236 days earlier.

1979 September 21              (3408)              Brian G. Marsden

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