Talk:Ecclesiastical new moon

This brief note seemed to need a little bit more.--Mockingbird0 (talk) 00:55, 3 September 2008 (UTC)

The problem with the table
The ecclesiastical moons are a date, not an instant. This is by design so that religious observances have a universal date, rather than varying with one's location on the globe. Assigning arbitrary instants for ecclesiastical moons (in an arbitrary time zone at that) is akin to insisting that, between leap years, the New Year shouldn't be celebrated until 06:00, 12:00 or 18:00 on January 1.

Beyond that, as this is an attempt to determine the recurrence of a Jewish holiday, traditional rules of timekeeping need to be observed. The first day of the new lunar month is the date that the moon is first visible after sunset with the unaided eye, and not necessarily the date containing the instant of a new lunation. If the moon is not sufficiently distant enough from the sun in the sky to be visible after the sun has set, the new month begins the next day.

I also suspect that days, in this application, will need to be reckoned as beginning at sunset rather than midnight.

The upshot is, in order to truly gauge the accuracy of the Gregorian lunar cycle, you will need a reference latitude as well as a reference longitude, and to determine local sunset at that point on the earth's surface on the dates in question. An extremely gross estimate can be used if you assume both sunset to always be 18:00 and that a lunation must be at least 6 hours old for the moon to be visible, but this is of dubious utility at best. —Preceding unsigned comment added by 108.110.132.90 (talk) 00:57, 16 November 2010 (UTC)