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IAUC 5872: PLUTO; N Sgr 1993

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                                                  Circular No. 5872
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)


PLUTO
     C. B. Olkin, Massachusetts Institute of Technology (MIT); S. W.
McDonald, MIT; and J. L. Elliot, MIT and Lowell Observatory, write:
"Recent astrometric measurements of Pluto-Charon and P20 (Mink et
al. 1991, A.J. 101, 2255; Dunham et al. 1991, A.J. 102, 1464) from
CCD strip scans at Lick Observatory (E. W. Dunham and C. Ford)
indicate that Pluto's shadow will pass several thousand kilometers
north of the earth, so that an occultation by Pluto will probably
not be visible.  However, depending on the exact northerly offset
of the Pluto-Charon system from the DE202 ephemeris, an occultation
of P20 by Charon may be visible from eastern Australia, Tasmania,
and/or western New Zealand.  High-quality observations of this
event could detect a tenuous atmosphere (Elliot and Young 1991,
Icarus 89, 244).  Potential observers should monitor the combined
light of Pluto, Charon, and P20 beginning about 15 min prior to and
after the nominal midtime of Oct. 3d08h58m UT.  Photometry should
have a time resolution of at least 0.2 sec."


NOVA SAGITTARII 1993
     P. Garnavich, Dominion Astrophysical Observatory, communicates:
"Another spectrogram of N Sgr 1993 was obtained with the 1.2-m
telescope at DAO on Sept. 27.19 UT.  The spectrum covered only the
region around H-alpha at a resolution of 0.13 nm.  H-alpha line
strength has doubled relative to the continuum since Sept. 18.  A
deep absorption feature has developed at a velocity of -1140 km/s.
The line has become box-shaped with more than 12 narrow emission
components on top."
     A. C. Gilmore, Mt. John University Observatory, reports the
following photometry with Johnson-Cousins UBVRcIc filters:  Sept.
27.40 UT, V = 9.57, U-B = -0.44, B-V = +0.24, V-Rc = +0.53, V-Ic =
+0.71 (1.31 air masses).  The star SAO 186455, located 5'.9 west
and 0'.6 north of the nova, was also measured as a possible comparison
star:  V = 9.31, U-B = -0.12, B-V = +0.08, V-Rc = +0.05, V-Ic
= +0.17 (1.35 air masses).  These stars were measured differentially
from the provisional comparison star SAO 186445 (assumed V =
7.747, U-B = -0.080, B-V = +0.079, V-Rc = +0.555, V-Ic = +0.16).
The assumed values appear good to +/- 0.015 in all but U-B, where
the uncertainty is +/- 0.03 magnitude.


1993 September 28              (5872)            Daniel W. E. Green

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