Astronomy and Astrophotography

Jeffrey Owen Katz, Ph.D.

Observatory Director, Custer Institute


Software for my "Discover Astronomy" class at the Custer Institute


Websites of Custer Members and Local Astronomy Groups


Celestial Navigation and the Problem of Longitude

Unlike latitude, which is easily determined from the position of the pole star or the noonday sun, longitude requires a comparison of local time (as determined from the positions of visible stars) with some form of universal time, for example, Greenwich Mean Time. Before the days of radio, those at sea had no way of accurately knowing the time in Greenwich against which local time could be compared in order to calculate longitude. Hence many ways to measure time--from clocks to the eclipses of Jupiter's moons--were explored. The problem with clocks was that they did not keep time accurately on long sea voyages. Given the difficulty estimating universal time, it is easy to see why longitude played center stage in the history of navigation.

Recommended Books

More books on astronomy can be found in the astronomy and astroimaging section of Jeffrey's books page

Valid HTML 4.0!


Copyright © 2005. Scientific Consultant Services, Inc.
Revised - 2005.09.11
Home Page: www.scientific-consultants.com
E-Mail: Jeffrey Owen Katz: jeffkatz@scientific-consultants.com
E-Mail: Donna McCormick: donnamccormick@scientific-consultants.com
Phone: 631-696-3333
Fax: 631-696-3333
Snail-Mail:  20 Stagecoach Road, Selden, NY 11784 (USA)