Central Bureau for Astronomical Telegrams
IAUC 2266: 1970g; THE EARTH'S SHADOW AND DEBRIS FROM COMET ENCKE
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Read IAUC 2267
Circular No. 2266
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
Western Union: RAPID SATELLITE CAMBMASS
COMET ABE (1970g)
The following precise positions have been reported:
1970 UT R. A. (1950) Decl. Mag. Observer
July 8.70729 2 19 01.73 +25 23 39.5 Otsubo
12.44752 2 19 41.57 +26 58 17.9 Van Biesbroeck
13.73566 2 19 45.37 +27 32 49.4 10.5 Urata
15.70972 2 19 52.86 +28 28 07.8 7 Tomita
15.73889 2 19 53.39 +28 29 51.9 "
K. Otsubo (Yamada, Fukuoka). Long. = -130o47', Lat. = +33o34'. 7.5-cm
f/4 lens. Measurer: T. Urata.
G. Van Biesbroeck (Lunar and Planetary Laboratory). 213-cm Kitt
Peak reflector.
T. Urata (Nihondaira Observatory). 10.2-cm f/5.4 lens. Image poor.
K. Tomita (Tokyo Astronomical Observatory, Dodaira station). Comet
diffuse with condensation. Communicated by M. Huruhata.
THE EARTH'S SHADOW AND DEBRIS FROM COMET ENCKE
Dr. R. G. Roosen, Goddard Space Flight Center, communicates:
"An observation on 1969 Feb. 21 seemed to indicate that the earth's
shadow was visible in the center of the gegenschein (Roosen 1969,
Dissertation, University of Texas). Since the shadow is not normally
detectable in the gegenschein, the observation was ascribed
to an enhancement in the amount of dust near the earth, and it was
suggested that the dust was in the orbital plane of P/Encke,
through which the earth was then passing. The material was
presumably blown out past the earth by solar radiation pressure.
Since the moon will be new near the time of passage of the earth
through the comet's orbit plane on 1971 Feb. 23-24, an excellent
opportunity then exists for confirming the 1969 observation. The
comet itself will have passed its descending node some six weeks
previously, and hence even more material might be expected. The
earlier observation showed the shadow to have a half-width of about
1o.5 and an intensity reduction of about 3 percent. Photoelectric
scans in declination of the region extending from 10o north to 10o
south of the anti-solar point yield the greatest possibility of
detecting the earth's shadow, and observations should if possible be
made near local midnight during the interval 1971 Feb. 20-28."
1970 July 21 (2266) Brian G. Marsden
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