Central Bureau for Astronomical Telegrams
IAUC 3061: Occn OF SAO 158687 BY URANIAN RINGS; 1977c; 1977b
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Read IAUC 3062
Circular No. 3061
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK Telex: 921428
Telephone: (617) 864-5758
OCCULTATION OF SAO 158687 BY URANIAN RINGS
S. D. Sinvhal, Uttar Pradesh State Observatory, reports that
four secondary occultations of SAO 158687 on Mar. 10 were observed
by H. S. Mahra and S. K. Gupta with the 104-cm reflector at Naini
Tal as shown below. The occultations can be identified with those
of Elliot et al. (IAUC 3051) and are therefore denoted accordingly:
Event UT Duration Event UT Duration
alpha1 20h32m01s 1s gamma1 20h27m19s 1s
beta1 20 30 25 1 delta1 20 26 15 1
The observations extended from 20h22m10s (i.e., after the epsilon
occultation occurred) to 21h30m UT with a break during 20h27m55s-20h28m40s.
M. K. V. Bappu, Indian Institute of Astrophysics, reports that
further examination of the Kavalur tracing (cf. IAUC 3048, 3051,
3058) reveals further occultations. He specifies the times with
reference to the middle of the epsilon5 event. The analysis below suggests
that the time for epsilon5 given on IAUC 3051 is most likely to be
correct, so the times for the other occultations become:
Event UT Event UT
alpha1 20h30m14s gamma1 20h25m44s
beta 20 28 43 delta1 20 24 44
On the assumption that the Elliot-et-al. alpha, beta, gamma and delta
rings are circular, centered on Uranus and in its equatorial plane, a
least-squares adjustment by B. G. Marsden using the 25 available
observations (see also IAUC 3051, 3058) yields the radii (in km and
with individual mean errors) listed below. The radii corresponding
to the other reported rings (using the midtimes specified for the
occultations) are also given:
Ring Distance Ring Distance
alpha3 42 550 delta 48 510 +/- 30
beta3 42 810 epsilon1,3,5 51 790 +/- 10
alpha 44 950 +/- 40 epsilon2,4 51 120 +/- 10
beta 45 890 +/- 30 zeta4 53 720
gamma 47 840 +/- 20
If the time given for epsilon5 on IAUC 3058 is adopted, the distances
corresponding to the Kavalur occultations are all increased by ~
150 km. The western (odd subscripts) and eastern (even subscripts)
sections of epsilon show that this ring is significantly asymmetric, but
although the p.a. at Uranus of the epsilon1 and epsilon2 events differs by
110o, that of the epsilon1 and epsilon2 events differs by as much as 8o.
With the Uranus-occultation duration of 25 (+/- 0.5) min given by Elliot
et al. for the Airborne Observatory (IAUC 3048) the radius of
Uranus (assumed to have circular cross-section) is 26 450 +/- 70 km.
COMET LOVAS (1977c)
The following precise positions have been reported:
1977 UT R. A. (1950) Decl. Observer
Mar. 12.66196 10 16 55.19 +33 54 43.2 Kosai
27.65243 10 06 12.38 +32 33 01.0 Seki
H. Kosai (Tokyo Observatory). Correction to IAUC 3055.
T. Seki (Kochi Observatory, Geisei Station).
The following improved orbital elements, by B. G. Marsden,
are based on eight observations Feb. 17 to Mar. 27:
T = 1976 Oct. 22.069 ET Peri. = 145.224
Node = 337.516 1950.0
q = 5.69669 AU Incl. = 64.420
1977 ET R. A. (1950) Decl. Delta r m2
Apr. 27 9 53.77 +28 59.2 5.531 5.853 17.9
May 7 9 52.51 +27 41.1
17 9 52.51 +26 21.4 5.875 5.888 18.0
27 9 53.65 +25 00.9
June 6 9 55.77 +23 40.3 6.222 5.925 18.2
16 9 58.72 +22 19.7
26 10 02.37 +20 59.4 6.540 5.966 18.3
July 6 10 06.59 +19 39.6
16 10 11.27 +18 20.3 6.805 6.010 18.5
PERIODIC COMET GRIGG-SKJELLERUP (1977b)
B. Blanco, Cerro Tololo Interamerican Observatory, provides
the following precise positions, obtained with the Curtis Schmidt
telescope in poor seeing and rather over exposed:
1977 UT R. A. (1950) Decl.
Apr. 1.35556 19 27 00.51 -48 41 01.6
1.39722 19 27 14.80 -48 33 49.3
1.40764 19 27 18.37 -48 32 07.8
J. Bortle, Brooks Observatory, describes the comet during Apr.
15.36-18.35 UT as of total visual magnitude 9.8 and coma diameter 4'
(32-cm reflector) and on Apr. 16-17 as 9.3 and ~ 6' (10 x 50 bin.).
1977 April 19 (3061) Brian G. Marsden
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