User Manual for
Lunar Calendars and Eclipse Finder
Ancient Eclipse Dates
For times in the distant past there is considerable uncertainty about the value of delta T. The uncertainty in the value of delta T outside the range -1000 CE through 2500 CE is too large for lunar phases and eclipse dates to be computed precisely, so Lunar Calendars and Eclipse Finder accepts dates only in the range -3200-01-01 CE through 6000-01-01 CE (or equivalents in other calendars).
To clarify, due to the uncertainty in delta T prior to -1000 CE the software computes dates and times accurately, but not precisely. Thus the time of an eclipse in the recent past may be computed with a precision of a few minutes, but the time of an eclipse in the distant past may have a precision of a few hours. The further back in the past, the less precise is the calculated time.
It is still possible, however, to compute the occurrence or non-occurrence of eclipses in the distant past, even if precise times are not possible. For example, eclipses are mentioned in the Indian epic the Mahabharata. Krishna and Mahabharata: Historical reality states that:
- The full moon and lunar eclipse at Krittika occurred on 29th September, 3067 B.C.
- The solar eclipse at Jyestha occurred on 14th October, 3067 B.C.
These are dates in the proleptic Julian Calendar. To check them using this software the year must be expressed in the astronomical system of year numbering: 3067 B.C. = -3066 CE.
Lunar Calendars and Eclipse Finder says that there was a penumbral lunar eclipse at -3066-09-29 JC 01:01 (using Indian timezone +5:30), which is 29th September, 3067 B.C. (Due to uncertainty in delta T, this eclipse might have occurred on 28th September.) The software also says that there was a total solar eclipse at -3066-10-14 JC 13:47, which is 14th October, 3067 B.C. Thus the software confirms both of the dates on that web page.
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