Earth rotation derived for occultation records
掩蔽観測から得られる地球回転
M. Soma, K. Tanikawa
相馬 充, 谷川清隆
Publ. Astron. Soc. Japan 68, Issue 2, id.29 8頁 (2016)
We determined the values of the Earth's rotation parameter,
ΔT = T T - UT, around AD 500 after confirming that the value of
the tidal acceleration, dot{n}, of the lunar motion
remained unchanged during the period
between ancient times and the present.
For determining of ΔT,
we used contemporaneous occultations of planets by the Moon.
In general, occultation records are not useful.
However, there are some records that give us a stringent condition
for the range of ΔT.
Records of the lunar occultations in AD 503 and AD 513 are
such examples. In order to assure the usefulness of
this occultation data,
we used contemporaneous annular and total solar eclipses,
which have not been used in the preceding work.
This is the first work in which the lunar occultation data have been
used as primary data to determine the value of
ΔT together with auxiliary contemporaneous annular and
total solar eclipses.
Our ΔT value is less than a smoothed value (Stephenson 1997)
by at least 450 s.
The result is consistent with our earlier results obtained
from solar eclipses.