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List of mutual planetary eclipses
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This is a List of mutual planetary eclipses, including occultations and transits.
Although mutual occultations of planets had been recorded in 581,[1] 1170,[2] 1590,[3] and 1737,[4] the first attempt to list past and future occultations of that nature was not made until 1970 during a manual search for conjunctions, in which Jan Meeus and Michael Walch discovered further occultations in 1522[a] and 1570,[b] published in 1970.[6] In 1977, Edwin Goffin calculated the occultations of certain planetary combinations for 1000–3000, but the results remained unpublished.[7]
The first table dedicated to mutual planetary occultations was published in 1979 by Steven Albers, who employed a Fortran program to assist in his calculations.[8] This table was extended back in time by Salvo De Meis in 1993.[9] Meeus recalculated mutual occultations for most of this period in 1998, extending it slightly further forward in time,[7] and in the same year the Pluto Project extended it far into the future.[10] The accuracy of more distant dates is suspect, especially for Mercury,[11] but no planet is exempt from error.[12] Despite this, occultation calculations have been carried out to extremely early and late dates.[13]
The visibility of the calculated occultations has been evaluated by multiple authors.[5][3] The tables have also been revised and extended even further back and forward in time.[13][11][14] But no evaluation is complete, and tables have yet to be computed for non-geocentric perspectives, although the concept has been explored more than once.[15][16] Very close conjunctions, such as that on 25 March -184, have been excluded from the list.[7][14]
Projected dates are not necessarily accurate before the 8th century BC or far into the future.[17] Going back in time, the Length of Day (LOD) on Earth was shorter, but it is not known exactly how much shorter thanks to a variety of factors still being debated. Earth's LOD difference (ΔT) is slight, but the cumulative time discrepancy from the earliest accurately dated solar eclipses to the time this discrepancy was first noticed is several hours. Because of this difference, the positions of objects in the sky as viewed from a given point on Earth's surface remain uncertain before the beginning of these records.[18][19] Although there has been much discussion on the relative contributions of these phenomena,[20] no accurate model for extrapolating beyond these early records yet exists.[21][22]
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Notes
- Elongation insufficient for visibility.
- "T" if total (occultation), "A" if annular (transit). Otherwise, "the maximum fraction of the occulted diameter" at the point of Earth's surface coming closst to the axis of the shadow is given (where the degree of occultation is the greatest).[7] If this has not been calculated, "P" for partial.[13]
Bibliography
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References
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