What kinds of astronomical lab activities can high school and college astronomy students carry out easily in daytime? The most impressive is the determination of latitude and longitude from observations of the Sun. The “shooting of a noon sight” and its “reduction to a position” grew to become a daily practice at the start of the 19th century1 following the perfection of the marine chronometer by John Harrison and its mass production.2 This technique is still practiced by navigators in this age of GPS. Indeed, the U.S. Coast Guard exams for ocean‐going licenses include celestial navigation.3 These techniques continue to be used by the military and by private sailors as a backup to all‐too‐fallible and jammable electronic navigation systems. A sextant, a nautical almanac,4 special sight reduction tables,5 and involved calculations are needed to determine position to the nearest mile using the Sun, Moon, stars, or planets. Yet, finding latitude and longitude to better than 30 miles from measurements of the Sun's altitude is easily within the capability of those taking astronomy or physics for the first time by applying certain basic principles. Moreover, it shows a practical application of astronomy in use the world over. The streamlined method described here takes advantage of the similar level of accuracy of its three components: 1.Observations using a homemade quadrant6 (instead of a sextant), 2. Student‐made graphs of the altitude of the Sun over a day7 (replacing lengthy calculation using sight reduction tables), and 3. An averaged 20‐year analemma used to find the Sun's navigational coordinates8,9 (rather than the 300+ page Nautical Almanac updated yearly).

1.
J. H. Moore, The New Practical Navigator, 18th ed. (S. Hamilton, Weybridge, England, 1810), pp. 207, 245–246.
2.
D. Sobel, Longitude (Walker & Company, New York, 1995).
3.
U.S. Coast Guard, Guide for Administration of Merchant Marine Deck Examinations (U.S. Dept. of Homeland Security, Washington, D.C., 2007), pp. 1–11.
4.
United Kingdom Hydrographic Office, 2008 Nautical Almanac, Commercial Edition (Paradise Cay Publications, Arcata, CA, 2007).
5.
National Imagery and Mapping Agency, Sight Reduction Tables for Air Navigation, H.O. 249 (National Geospatial‐Intelligence Agency, Bethesda, MD, 2007).
6.
F. W. Wright, Particularized Navigation, Part II (Cornell Maritime Press, Cambridge, MD, 1973), pp. 67–68.
7.
B. J. Bok and F. W. Wright, Basic Marine Navigation (Houghton Mifflin, Cambridge, MA, 1952), p. 293.
8.
C. A. Whitney and F. W. Wright, Learn to Navigate (Cornell Maritime Press, Cambridge, MD, 1992), pp. 271–272.
9.
Samuel G.
Shaw
, “
Resurrecting the analemma
,”
Navigation
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1
),
1
5
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2000
).
10.
K. J. Schoon, “Misconceptions in Earth and Space Sciences, A Cross‐Age Study,” PhD dissertation, Loyola University, 1988.
11.
P. M. Sadler, “The Initial Knowledge State of High School Astronomy Students,” EdD dissertation, Harvard University, 1992, p. 104.
12.
N. F. Comins, Heavenly Errors (Columbia University Press, New York, 2001), pp. 47, 98.
13.
Use the opposite convention for the Eastern Hemisphere since longitude diminishes in magnitude moving west: Add to (if east) or subtract from (if west) the longitude of your time zone meridian.
14.
Navigators prefer methods to keep sign errors at bay by avoiding negative numbers whenever possible (unlike physicists, who do not have to contend with seasickness, gales, etc.). The general rule for finding latitude requires that you note if your zenith is north or south of Sun (always north above the Tropic of Cancer and south belowthe Tropic of Capricorn). If the hemisphere you are in (North or South) is the same as the direction of zenith position from the Sun, add your declination to your zenith distance. If the hemisphere you are in is contrary to your hemisphere, subtract your declination from your zenith distance.
15.
www.jgiesen.de/SME/index.htm.
16.
tycho.usno.navy.mil/what1.html.
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