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IAUC 6232: P/1995 S1 = P/1846 D1

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                                                  Circular No. 6232
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)


COMET P/1995 S1 = P/1846 D1 (DE VICO)
     Preliminary orbital elements, from 39 observations Sept. 17-20,
bear a striking resemblance to those of D/1846 D1 (1846 IV).
Though the predictions were known to have an uncertainty of several
years, R. J. Buckley (1979, JBAA 89(3), 260) had calculated T =
1996 July 3.  It has not been possible to link the two apparitions,
despite great effort to do so, probably because of nongravitational
forces that require a longer arc of observation at the current
return.  The following orbital elements by the undersigned were
computed from an unpublished 1846 orbit utilizing 17 observations
1846 Feb. 27-Apr. 27 (mean residual 2".9); the observations had
been re-reduced recently by B. G. Marsden using the new PPM Star
Catalogue and a computer program written by G. V. Williams.  The
resulting orbit was adjusted (with full perturbations) so that e in
1846 produced an orbit with T about 1995 Oct. 6, which is the value
found by performing a 2-body calculation using the 1995 observations
alone; the 1995-epoch elements from the 1846 observations were then
differentially corrected (2-body calculation) while holding e and q
fixed (and solving for T and the angles):

     T = 1995 Oct.  6.026 TT          Peri. =  12.978
     e = 0.96274                      Node  =  79.626   2000.0
     q = 0.65891 AU                   Incl. =  85.382
       a = 17.68245 AU     n = 0.013255     P =  74.36 years

These elements suggest T around 1922 Apr. for the comet's last
(missed) return to perihelion.  Crommelin (1917, JBAA 27, 265; 1920,
JBAA 30, 135) suggested that the most probable T at its first
predicted return was around 1921 Nov., though search ephemerides
were provided for several years.  Ephemeris from the above elements:

1995 TT     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Sept.20     9 11.46   - 0 19.5   1.157   0.737   39.1   59.2    6.5
     22     9 19.30   + 1 42.4   1.129   0.720   38.9   61.1    6.3
     24     9 27.80   + 3 50.1   1.102   0.704   38.7   63.0    6.2
     26     9 37.07   + 6 03.3   1.076   0.691   38.6   64.9    6.1
     28     9 47.19   + 8 21.5   1.052   0.680   38.5   66.8    5.9
     30     9 58.24   +10 43.4   1.030   0.671   38.5   68.5    5.8


1995 September 20              (6232)            Daniel W. E. Green

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