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IAUC 5663: 1992t

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                                                  Circular No. 5663
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


PERIODIC COMET SWIFT-TUTTLE (1992t)
     L. McFadden, University of Maryland, reports that spectroscopic
observations (range 380-525 nm) of P/Swift-Tuttle made on Oct. 5.097
UT by D. Schleicher, R. Schultz, A. Chamberlin, and herself with the
1.8-m Perkins Telescope at Lowell Observatory (+ Ohio State CCD
spectrograph) yield the following production rates, following a
preliminary reduction by Schultz: log Q(CN) = 26.77, log Q(C3)
= 25.72, log Q(C2) = 26.49.

      M. A'Hearn, University of Maryland, communicates: "Observations of
P/Swift-Tuttle by L. McFadden, P. Feldman, M. Haken, J. McPhate, and
myself using the International Ultraviolet Explorer yield the
following respective water production rates (standard vectorial
model, in units of 10**29 molecules/s): Nov. 3.1 UT, 1.5; 3.9,
2.2; 4.4, 2.5; 16.0, 3.4; 23.9 approx. 5.  CS production is roughly
0.2 percent, as in P/Halley, but higher than in most comets.
Relative abundance can be significantly affected by phase lags
during variability.  The continuum brightness implies a gas-to-dust
ratio comparable to but slightly higher than that of P/Halley.
Photometric variability during the shifts indicates that periodic
variations must have periods considerably greater than 16 hr."

      H. Mikuz, Ljubljana, Slovenia, reports that several 10-min CCD
frames obtained around Nov. 19.78 and 20.75 UT, with a 250-mm f/4 lens
and an H2O+ 620-nm filter, show a straight ion tail about 4.5 deg long
in p.a. 41 deg.  Similar frames on Nov. 23.73-23.77 show a straight
ion tail about 6.7 deg long in p.a. 44 deg, when a red continuum filter
(647 nm) showed a fan of dust about 2 deg long extending in p.a. 10-40
deg.  Both filters have FWHM = 10 nm.  Clouds and knots of material are
present along the tail stream on all three nights.

     Further total visual magnitude estimates: Nov. 14.75 UT, 5.0 (A.
Boattini, Piazzano, Italy, naked eye); 15.70, 5.3 (O. Midtskogen,
Tranby, Norway, 0.05-m refractor); 17.78, 4.9 (T. Vanmunster, Landen,
Belgium, 0.12-m reflector); 18.69, 5.0 (A. Kereszturi, Budapest,
Hungary, 20 x 60 binoculars); 20.95, 4.9 (D. W. E. Green, Cambridge,
MA, 12 x 50 binoculars); 21.69, 5.5 (H. Dahle, Oslo, Norway, 7 x 50
binoculars); 22.38, 4.6 (M. Ohkuma, Mt. Fuji, Japan, 10 x 70
binoculars); 23.74, 5.4 (R. Behrend, La Chaux-de-Fonds, Switzerland,
10 x 40 binoculars); 25.11, 5.0 (C. S. Morris, La Canada, CA, 10 x 50
binoculars).


1992 November 27               (5663)            Daniel W. E. Green

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