User Manual for
Lunar Calendars and Eclipse Finder
Finding Moon Phases and Eclipses

This program finds the next or previous:

  • Full moon
  • Dark moon
  • Half moon (1st quarter)
  • Half moon (last quarter)
  • Quarter
  • Lunar or solar eclipse
  • Lunar eclipse
  • Total lunar eclipse
  • Total or partial lunar eclipse
  • Solar eclipse
  • Total solar eclipse
  • Annular solar eclipse
  • Eclipse in same saros series
  • Coincidence of 1sts of months, i.e., a day when dates in four lunar calendars (ARC, MP, MMG and LLT) have day = 1.

In order of decreasing visibility, lunar eclipses are termed total, partial and penumbral. In a total lunar eclipse the Moon enters the Earth's umbra entirely; in a partial lunar eclipse it enters the Earth's umbra only partially; and in a penumbral lunar eclipse it does not enter the Earth's umbra at all, but merely passes through its penumbra (and the eclipse is mostly invisible).

When an eclipse is found the time given for the eclipse is the time of the maximum eclipse. For lunar eclipses the maximum eclipse is visible at the stated time (GMT) over most of the hemisphere of the Earth which is facing the Moon. For solar eclipses the situation is different. The time given for the solar eclipse is the time of maximum eclipse (GMT) from a geocentric point of view (as if an observer were located at the center of the Earth). This is usually not the same as the time of maximum eclipse from the point of view of a person somewhere along the path traced by the shadow of the Sun along the surface of the Earth. For an observer located at the start of the eclipse track the eclipse will occur some hours before the time calculated by this software, and for an observer located at the end of the eclipse track the eclipse will occur some hours later.

The time of the maximum point of eclipse is usually not exactly the same as the time of the full moon or dark moon, although in the case of solar eclipses the time of the maximum and the time of the dark moon are usually only minutes apart.

The saros number is the number of the saros series (or family) containing the eclipse (saros numbers range from 1 through 223). A saros series lasts for about 1,300 years, so eclipses a millennium apart may have the same saros number. Two eclipses in the same saros series are separated by 223 lunations, i.e., 6585.32 days (this is called a saros period).

A search for a day on which all four of the lunar calendars other than the Hermetic Lunar Week Calendar have day 1 does not consider that calendar because in that calendar the dark moon can occur on day 1 or on any of day 7, day 8 and day 9 in the last week of the preceding month. Such coincidences occur about once per year, e.g., on the following dates in the CE calendar: 2012-08-17, 2014-03-31, 2014-09-24, 2017-04-26 and 2017-10-20.

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