सिद्धान्तदर्पण (महामहोपाध्याय सामन्त चन्द्रशेखर सिंह - नग्न-नेत्र खगोल वेध एवं गणित महाकोश)

Introduction xxxix
ephemeris is correct, and how much confidence may
be placed in it. For rough comparison, the places
of the planets computed by him are shown below,
toegther with their places, first according to the
British Nautical almanac, and next according to a
widely circulated Bengali almanac said to have been
computed after the Surya-Sidhanta. The correction
for precession in the places given in the Bengali
almanac has been made by adding 20°54′ to them
in accordance with the almanac. Besides these, I
append ephemeris for two other days from the
Nautical almanac and the Siddhanta-Darpana.
For various reasons, neither Chandrasekhara's,
nor for that matter - any other Hindu almanac can
coincide with the Nautical almanac. Neglecting
minor corrections unknown in our almanacs, there
is the determination of the exact amount of
precession, without which no comparison is
possible with European almanacs. To avoid it, the
relative distance of the planets may be taken. It will
be seen that while the Bengali almanac may be in
error by as much as 4°, the error in the ephemeris
by the Siddhanta-Darpana is limited to
half-a-degree. The reader will, however, remember
that a Hindu astronomer depends upon unaided
vision, and is satisfied if the longitudes are correct
to a half degree. Accepting this as our standard,
the ephemerides by the Siddhanta-Darpana
compare favourably with those of the N.A., while
the greater discrepancies in the Bengali almanac
conclusively prove how urgent has been the
question of the revision of our existing almanacs in
the light of observations now made. (See Table )