Volume 9, Issue 1, March 2021, Page: 1-7
Calculation of Solar Motion for Localities in the USA
Keith John Treschman, Science/Astronomy, University of Southern Queensland, Toowoomba, Australia
Received: Dec. 17, 2020;       Accepted: Dec. 31, 2020;       Published: Jan. 12, 2021
DOI: 10.11648/j.ajaa.20210901.11      View  9      Downloads  8
Abstract
Even though the longest day occurs on the June solstice everywhere in the Northern Hemisphere, this is NOT the day of earliest sunrise and latest sunset. Similarly, the shortest day at the December solstice in not the day of latest sunrise and earliest sunset. An analysis combines the vertical change of the position of the Sun due to the tilt of Earth’s axis with the horizontal change which depends on the two factors of an elliptical orbit and the axial tilt. The result is an analemma which shows the position of the noon Sun in the sky. This position is changed into a time at the meridian before or after noon, and this is referred to as the equation of time. Next, a way of determining the time between a rising Sun and its passage across the meridian (equivalent to the meridian to the setting Sun) is shown for a particular latitude. This is then applied to calculate how many days before or after the solstices does the earliest and latest sunrise as well as the latest and earliest sunset occur. These figures are derived for 60 cities in the USA. The selection was initially based on the most populous urban areas but was extended to ensure that each of the 50 states has a representative city.
Keywords
Solstice, Elevation, Obliquity, Elliptical Orbit, Meridian, Analemma, Equation of Time
To cite this article
Keith John Treschman, Calculation of Solar Motion for Localities in the USA, American Journal of Astronomy and Astrophysics. Vol. 9, No. 1, 2021, pp. 1-7. doi: 10.11648/j.ajaa.20210901.11
Copyright
Copyright © 2021 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Reference
[1]
astropixels.com/ephemeris/astrocal/astrocal2020cst.html.
[2]
P. Kenneth Seidelmann (ed), Explanatory Supplement to the Astronomical Almanac, University Science Books, Sausalito California, 2006.
[3]
Teo Shin Yeow, The Analemma for Latitudinally-Challenged People, http://www.math.nus.edu.sg/aslaksen/projects/tsy.pdf, Singapore, 2002.
[4]
D. Fletcher, Solar Declination, http://holodeck.st.usm.edu/vrcomputing/vic_t/tutorials/solar/declination.shtml, 2002.
[5]
Peter Duffett-Smith, Practical Astronomy with your Calculator, 3rd edition, Cambridge University Press, 1992.
[6]
James B. Kaler, The Ever-Changing Sky – A Guide to the Celestial Sphere, Cambridge University Press, Cambridge, 2002.
[7]
H. R. Mills, Positional Astronomy and Astro-Navigation Made Easy, Stanley Thornes Ltd., 1978.
[8]
Ian Ridpath (ed), Norton’s 2000.0 Star Atlas and Reference Handbook, 18th edition, Longman Group UK Ltd. Essex.
[9]
Stan Wagon, “Why December 21 is the Longest Day of the Year”, Mathematics Magazine, 63, 1990, 307-311.
Browse journals by subject