Sunrise -- from Eric Weisstein's World of Astronomy

Sunrise is the time at which the leading limb of the Sun first rises above the horizon. The effect of refraction in the Earth's atmosphere lifts the image of the Sun about half a degree at the horizon, making sunrise about two minutes earlier than would be expected from the actual position of the Sun in space. Refraction and the fact that sunrise and sunset are calculated from the limb (and not the center) slightly lengthen "day" relative to "night."

The above plot shows the time of sunrise from Chicago in U.S. Central Standard Time, so actual times must be shifted to account for daylight saving time. In 1999, the earliest and latest sunrises occur on June 14 at 5:23 CST and January 4-5 at 8:15 CST, respectively.

Bretagnon, P. Planetary Programs and Tables from -4000 to +2800: Tables for the Motion of the Sun and the Five Bright Planets. Richmond, VA: Willmann-Bell, 1986.

Casey, B. "Astronomical Sky Calendar." http://imagiware.com/astro/skycalendar.cgi.

Dershowitz, N. and Reingold, E. M. Calendrical Calculations: The Millennium Edition. Cambridge, England: Cambridge University Press, 1999.

Duffett-Smith, P. "Rising and Setting" and "The Sun." §33 in Practical Astronomy with Your Calculator, 3rd ed. Cambridge, England: Cambridge University Press, pp. 52-55 and pp. 83-100, 1992.

European Southern Observatory. "ESO Sky Calendar Tool." http://www.eso.org/observing/proposals/skycalc.html.

Kaler, J. B. The Ever-Changing Sky: A Guide to the Celestial Sphere. New York: Cambridge University Press, 1996.

Montenbruck, O. and Pfleger, T. "Rising and Setting Times" and "The SUNSET program." §3.6 and 3.8 in Astronomy on the Personal Computer, 4th ed. Berlin: Springer-Verlag, pp. 47-48 and 50-57, 2000.

Seidelmann, P. K. Explanatory Supplement to the Astronomical Almanac. Mill Valley, CA: University Science Books, pp. 482-493, 1992.

United States Government Printing Office. "Sunrise and Sunset." The Astronomical Almanac for the Year 2000. Washington, DC: U. S. Government Printing Office, pp. A14-A21, 1997.

U.S. Naval Observatory. "Sunrise/Sunset/Twilight and Moonrise/Moonset/Phase." http://tycho.usno.navy.mil/srss.html.

U.S. Naval Observatory. "Calculation: Rise, Set, and Transit Times." http://mach.usno.navy.mil/cgi-bin/aa_micaform2?calc=20&ZZZ=END.