Daytime Celestial Navigation for the Novice

• Autores: Philip M. Sadler, Kristopher Night
• Localización: The Physics Teacher, ISSN 0031-921X, Vol. 48, Nº. 3, 2010, págs. 197-199
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • 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 century1following the perfection of the marine chronometer by John Harrison and its mass production.2This technique is still practiced by navigators in this age of GPS. Indeed, the U.S. Coast Guard exams for oceangoing licenses include celestial navigation.3These techniques continue to be used by the military and by private sailors as a backup to alltoofallible and jammable electronic navigation systems. A sextant, a nautical almanac,4special sight reduction tables,5and 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 Suns 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 quadrant6instead of a sextant, 2. Studentmade graphs of the altitude of the Sun over a day7replacing lengthy calculation using sight reduction tables, and 3. An averaged 20year analemma used to find the Suns navigational coordinates8,9rather than the 300 page Nautical Almanacupdated yearly.