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IAUC 3515: 1978 P 1; Occns BY NEPTUNE; Occn BY URANUS; 1980g

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                                                  Circular No. 3515
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

1978 P 1
     R. S. Harrington and J. W. Christy, U.S. Naval Observatory
communicate: "The speckle observations of 1978 P 1 reported on IAUC
3509, when compared to positions computed from an orbit that allows
for the motion of Pluto, give separation residuals of -0".04 and
+0".01, yielding an orbital radius at the epoch of observation of
0".89, or 19 000 km.  This yields a mass of 0.0024 earth masses -
and a density of 0.0004 kg m**-3 if the reported diameter is

     P. Nicholson reports the incomplete observation by T. J. Jones
and himself at Mt. Stromlo Observatory of the Aug. 21 occultation
by Neptune of star 23 in the list by Klemola et al. (1978, A.J. 83,
205).  Emersion half-light occurred at 12h49m47s +/- 5s UT and was
accompanied by at least ten sharp spikes.  Immersion was not observed
because of clouds, but it occurred before 11h51m30s UT, implying an
occultation chord length of at least 18 500 km.  Observations were
continued until 14h17m22s UT.  A possible secondary occultation of
duration 1.5 s and depth 0.7 was observed at 13h44m01s UT,
corresponding to a radius of ~ 1.5 RN in Neptune's equatorial plane.
The Aug. 15 appulse to star 22 in the list was monitored, but no
occultation was observed.  Information about other positive
photoelectric observations of the Aug. 21 event is solicited.

     P. Bouchet and C. Perrier, European Southern Observatory, inform
us that the additional occultations a-g reported by them during
the Aug. 15-16 event (cf. IAUC 3503) have not been confirmed by
Las Campanas and Cerro Tololo observers.  They thus have some
reservations about the reality of these occultations.  However, they
were not caused by clouds and do not seem to be due to some effect
in the photometer.

     Total visual magnitude estimates and coma diameters by J.
Bortle, Stormville, NY (0.32-m reflector): Sept. 7.35 UT, m1 = 13.1,
d = 0'.9; 9.35, 13.1, 0'.8; 11.37, 12.8, 1'.1.

1980 September 16              (3515)              Brian G. Marsden

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