Ecclesiastical new moon: Difference between revisions
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An '''ecclesiastical new moon''' is the first day of a lunar month (an ecclesiastical moon) in an [[computus|ecclesiastical lunar calendar]]. Such months have a whole number of days, 29 or 30, whereas true [[synodic month]]s can vary from about 29.27 to 29.83 days in length. Medieval authors equated the ecclesiastical new moon with a new crescent moon, but it is not a phase of the true moon. If the ecclesiastical lunar calendar is accurate, the ecclesiastical new moon can be any day from the day of the astronomical [[new moon]] or [[dark moon]] to two days later (see table). |
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[[Image:BritLibCottonCleoBIXLiturgicalCalOct.jpg| thumb | right | Calendar page from a 13th-century liturgical book.([[British Library]], Cotton MS Cleopatra B IX, folio 59r). The Golden numbers, indicating the ecclesiastical new moons, are in the fifth column from the left-hand margin, to the left of the [[Dominical letter|Sunday letters]]]] |
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The ecclesiastical new moon which falls on or next after March 8 is of special importance, since it is the paschal new moon that begins the paschal lunar month (see table). The fourteenth day of the same lunar month is the first of the calendar year to occur on or next after March 21. This fourteenth day was called the ''[[paschal full moon]]'' by medieval computists. [[Easter]] is the following Sunday. |
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The Jewish festival of Passover lasts a week and runs from the fifteenth to the twenty-first day of the first Jewish month. The first Easter Sunday fell on the Sunday of that week. |
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As in all lunar calendars, months generally have 29 and 30 days alternately. Medieval authors equated the ecclesiastical new moon with a new crescent moon, but a great deal cannot be read into that as until the reform of the calendar (and still in the Julian calendar) there is a steadily increasing distance between the astronomical new moon and the ecclesiastical new moon. The ecclesiastical new moon which falls on or next after March 8 is of special importance, since it is the paschal new moon that begins the paschal lunar month (see table). The fourteenth day of the same lunar month is the first of the calendar year to occur on or next after March 21. This fourteenth day was loosely called the ''[[paschal full moon]]'' by medieval computists. [[Easter]] is the following Sunday. |
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Calendar pages in medieval liturgical books indicated the ecclesiastical new moons by writing the [[Golden numbers|Golden Number]] to the left of the day of the month on which the ecclesiastical new moon would occur in the year of that Golden Number. In some places the age of the moon was announced daily in the office of [[Prime_(liturgy) | Prime]] at the reading of the [[Roman martyrology | martyrology]].<ref>At medieval [[Exeter Cathedral]], it was the next day's date and age of the moon that were announced. ''Et omnibus in locis suis sedentibus sit ibi quidam puer...paratus ad legendum leccionem de Martilogio, absque Iube domine, sed pronunciondo primo loco numerum Nonarum, Iduum, Kalendarum, et etatem lune qualis erit in crastino...'' (And when all are sitting in their places let a boy be there ready to read the Martyrology beginning with Iube domine, but first saying the number of Nones, Ides, Kalends, and what the age of the moon will be on the morrow...) J.N. Dalton, ed., ''Ordinale Exon.'' vol. 1, Henry Bradshaw Society, London, 1909, p. 37.</ref> |
Calendar pages in medieval liturgical books indicated the ecclesiastical new moons by writing the [[Golden numbers|Golden Number]] to the left of the day of the month on which the ecclesiastical new moon would occur in the year of that Golden Number. In some places the age of the moon was announced daily in the office of [[Prime_(liturgy) | Prime]] at the reading of the [[Roman martyrology | martyrology]].<ref>At medieval [[Exeter Cathedral]], it was the next day's date and age of the moon that were announced. ''Et omnibus in locis suis sedentibus sit ibi quidam puer...paratus ad legendum leccionem de Martilogio, absque Iube domine, sed pronunciondo primo loco numerum Nonarum, Iduum, Kalendarum, et etatem lune qualis erit in crastino...'' (And when all are sitting in their places let a boy be there ready to read the Martyrology beginning with Iube domine, but first saying the number of Nones, Ides, Kalends, and what the age of the moon will be on the morrow...) J.N. Dalton, ed., ''Ordinale Exon.'' vol. 1, Henry Bradshaw Society, London, 1909, p. 37.</ref> |
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Revision as of 17:38, 8 August 2010
An ecclesiastical new moon is the first day of a lunar month (an ecclesiastical moon) in an ecclesiastical lunar calendar. Such months have a whole number of days, 29 or 30, whereas true synodic months can vary from about 29.27 to 29.83 days in length. Medieval authors equated the ecclesiastical new moon with a new crescent moon, but it is not a phase of the true moon. If the ecclesiastical lunar calendar is accurate, the ecclesiastical new moon can be any day from the day of the astronomical new moon or dark moon to two days later (see table).
The ecclesiastical new moon which falls on or next after March 8 is of special importance, since it is the paschal new moon that begins the paschal lunar month (see table). The fourteenth day of the same lunar month is the first of the calendar year to occur on or next after March 21. This fourteenth day was called the paschal full moon by medieval computists. Easter is the following Sunday.
Calendar pages in medieval liturgical books indicated the ecclesiastical new moons by writing the Golden Number to the left of the day of the month on which the ecclesiastical new moon would occur in the year of that Golden Number. In some places the age of the moon was announced daily in the office of Prime at the reading of the martyrology.[1]
When in the 13th century Roger Bacon complained about the discrepancy between the ecclesiastical moon and the observed lunar phases, he specifically mentioned the discrepancy involving the ecclesiastical new moon
Quilibet computista novit quod fallit primatio per tres dies vel quatuor his temporibus; et quilibet rusticus potest in coelo hunc errorem contemplari. (Any computist knows that the prime [of the moon] is off by three or four days in our time; and any rustic can see this error in the sky.)[2]
These complaints were finally addressed by the construction of the Gregorian calendar.
A check can be made on the phase difference between the astronomical new moon and the ecclesiastical new moon. In the following table a reference time of 6 A.M. on the last day of a 30-day month and 6 P.M. on the last day of a 29-day month is compared with the times of the astronomical new moon in 2010. All times are Greenwich Mean Time, which is the same as Co-ordinated Universal Time.
| New Moon[3] | Reference Time[4] | Difference |
|---|---|---|
| January 15d 07h | January 16d 06h | +23h |
| February 14d 03h | February 14d 18h | +15h |
| March 15d 21h | March 16d 06h | +09h |
| April 14d 12h | April 14d 18h | +06h |
| May 14d 01h | May 14d 06h | +05h |
| June 12d 11h | June 12d 18h | +07h |
| July 11d 20h | July 12d 06h | +10h |
| August 10d 03h | August 10d 18h | +15h |
| September 8d 10h | September 9d 06h | +20h |
| October 7d 19h | October 8d 18h | +23h |
| November 6d 05h | November 7d 06h | +1d 01h |
| December 5d 18h | December 6d 18h | +1d 00h |
| Year | Gregorian paschal new moon | Days in paschal lunar month |
|---|---|---|
| 1995 | April 1 | 29 |
| 1996 | March 21 | 29 |
| 1997 | March 10 | 29 |
| 1998 | March 29 | 29 |
| 1999 | March 18 | 29 |
| 2000 | April 5 | 30 |
| 2001 | March 26 | 29 |
| 2002 | March 15 | 29 |
| 2003 | April 3 | 29 |
| 2004 | March 23 | 29 |
| 2005 | March 12 | 29 |
| 2006 | March 31 | 29 |
| 2007 | March 20 | 29 |
| 2008 | March 9 | 29 |
| 2009 | March 28 | 29 |
| 2010 | March 17 | 29 |
| 2011 | April 4 | 30 |
| 2012 | March 25 | 29 |
| 2013 | March 14 | 29 |
References
- ^ At medieval Exeter Cathedral, it was the next day's date and age of the moon that were announced. Et omnibus in locis suis sedentibus sit ibi quidam puer...paratus ad legendum leccionem de Martilogio, absque Iube domine, sed pronunciondo primo loco numerum Nonarum, Iduum, Kalendarum, et etatem lune qualis erit in crastino... (And when all are sitting in their places let a boy be there ready to read the Martyrology beginning with Iube domine, but first saying the number of Nones, Ides, Kalends, and what the age of the moon will be on the morrow...) J.N. Dalton, ed., Ordinale Exon. vol. 1, Henry Bradshaw Society, London, 1909, p. 37.
- ^ Roger Bacon, Opus Tertium LXX, in J. S. Brewer, ed., Fr. Rogeri Bacon Opera quaedam hactenus Inedita. Vol. 1. H.M. Stationery Office, 1859 (Kraus Reprint 1965), p. 282.
- ^ From the U.S. Naval Observatory's Principal phase calculator
- ^ From the Explanatory Supplement to the Ephemeris and the American Ephemeris and Nautical Almanac, H. M. Stationery Office, London, 1966, fourth revised printing, 1977, page 426.