The NOAA has a page describing the sunrise calculation here (pdf).
Jewish Calendar References
The algorithms for hebcal were taken from
calendar routines by
Edward M. Reingold and
Their program is extremely clear and provides many instructive
examples of fine calendar code in emacs-LISP.
- Understanding the Jewish Calendar
- by Rabbi Nathan Bushwick. A well written treatment of the Jewish Calendar. Good bibliography.
- Encyclopedia Judaica
- Always the right place to start. Check out their entry on Calendar
- Calendrical Calculations
- Reingold and Dershowitz's own text. A keeper.
Other Good References
- Hebrew Calendar
Science and Myths
- Fun stuff, page with neat-o facts about the
arithmetic of the Jewish Calendar and its consequences.