Add Lunation Number

[jasonsturges]

Per discussion #1, adding Brown Lunation Number (BLN).

Lunation Number

Brown Lunation Number (BLN), per Wikipedia:

...defines lunation 1 as beginning at the first new moon of 1923, the year when Ernest William Brown's lunar theory was introduced in the American Ephemeris and Nautical Almanac.[citation needed] Lunation 1 occurred at approximately 02:41 UTC, January 17, 1923.