Topband: Sunrise/Sunset Times

[Bill Tippett]

	What is the sunrise/sunset?  Several have asked
recently so I decided to do a few comparisons.  For an
example I used my own coordinates 35 26 N 80 15 E
(deg/min).  Here are the results for April 1:

Source	SR	SS	Notes

DX Telnet	1106	2342 SH/SU after entering my exact lon/lat
DX Atlas	1108	2342
DX Aid	1108	2342
W6ELProp	1111	2338
USNO		1107	2343 http://aa.usno.navy.mil/data/docs/RS_OneDay.html
WSOC-TV*	1108	2341 (for 35 27 N 80 10 E)

*Local TV station webpage customized for New London, NC
coordinates of 35 27 N 80 10 W.

Why is W6ELProp so far off?  Probably because he uses
a different definition of sunrise and sunset.  I believe most
of the others use 0.75 degrees below the horizon since
the atmosphere refracts the light and makes it appear the
sun comes up earlier and sets late than is actually the
case.  I've searched many times but never found a way to
correct this in W6ELProp.

	The most critical thing with any of these programs
is to make sure you have the coordinates right.  Many of
the ham programs only give you the center of the country
which can vary greatly for large geographic areas like UA0,
VK or W.  One of the neat features of DX Atlas is that it
has a very good database of cities, islands and even sub-
regions like the Russian oblasts.  For example you can
easily see the large difference between UA0Z and UA0K
with the click of a mouse after expanding UA0.

				73,  Bill  W4ZV