Gemelos de Minnesota

The inex is one duration equal to 358 lunations (or synodical months), that is to say approximately 28 years and 50 weeks.

The inex with the property interesting to be also close to an half-entirety number of times the value of the draconitic month, this makes it useful for the prediction of the eclipse S of Sun and the Moon. Indeed, an eclipse can take place only if two simultaneous conditions are observed:

  • Full moon or the New moon (Syzygy)
  • passage of the Moon to a node (ascending or descendant)

For example, if one takes as starting point an eclipse with the following configuration:

  • the New moon (eclipse of the sun)
  • the Moon with the ascending node
After one duration of a inex, the configuration will be:
  • the New moon (by definition of the inex)
  • the Moon close to the node descending (except for less 0,1°)
A new eclipse of the sun will be able to take place.

Owing to the fact that the inex has a value close to an integer of days (10 571,95 days), the localization of this eclipse will be close to the eclipse of origin in longitude.

History

This cycle was described by Andrew Crommelin in 1901 and studied per G. van den Bergh in 1955, which gave him its current name.

See too

References

  • A.C.D. Crommelin (1901): The 29-year eclipse cycles. Observatory xxiv nr.310, 379, Oct.-1901
  • G. van den Bergh (1954): Eclipses in the second millennium B.C. Tjeenk Willink & Zn NV, Haarlem 1954
  • G. van den Bergh (1955): Periodicity and Variation off Solar (and Lunar) Eclipses, 2 flights. Tjeenk Willink & Zn NV, Haarlem 1955

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