Sunrise and sunset times
Sunrise and sunset times of past years can be found in the South Australian Government Gazette.
Background to sunrise and sunset times
Sunrise and sunset times were originally provided as a means of establishing when vehicle lights should be turned on.
The times are checked using:
The published times are computed and are not observed or recorded events. The computations assume certain ideal conditions and the data might not be relevant to a specific case.
The times are intended for general public use, not for litigation purposes.They are provided as a prima facie proof of sunrise and sunset and acceptance by a court for other purposes is not guaranteed.
The sunrise and sunset times are calculated by interpolation from tables in the Astronomical Phenomena publication for each year. This almanac of sun and moon times is prepared jointly by the United States Naval Observatory and Her Majesty's Nautical Almanac Office.
The calculated times are within one minute of each other.
Times are dependent on the latitude and longitude of observing the phenomena and also the time zone applicable to that area. The old Adelaide Observatory location is used for convention, Latitude: South 34˚ 56' Longitude: East 138˚ 36' and the time zone (Adelaide is 9.5 hours in advance of Greenwich Mean Time).
Other factors have a small affect on the times too. Variations from the calculated times may be due to refraction and the relative heights of the observer and horizon. The observed times will differ by approximately four minutes for every degree of longitude from Adelaide; for example, add four minutes for Whyalla, add 20 minutes for Ceduna, and subtract eight minutes for Mount Gambier.
The times of sunrise and sunset are the instant the upper edge of the sun appears to lie on the horizon for an observer at sea level. An allowance of 34' has been made for refraction and a further 16' has been made for the semi-diameter of the sun. The sun's parallax, maximum 0'09" is ignored because it is far smaller than the uncertainty in the adopted value for refraction.
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