Sunrise, Sunset, and LAN
To get sunrise, sunset, twilight times and LAN and other data, set the Latitude and date of interest in the Main Input Window and then press the Sun button to get the following screen. The output is described below.
The UT dates are repeated and may be different
from the one selected if there is no phenomena on the date requested. Also
the rise or set may occur on a date different from the one selected.
Sunrise/set = time of upper limb on the visible horizon
LAN = the time of Meridian Passage of the sun.
Equation of time is the difference between LAN and 1200 LMT
Hc = peak height of the sun at LAN
Zn rise/set = the bearing of the sun center at time of sunrise/set
AM/PM twilight = halfway between civil and nautical twilight
AM/PM GHAA = GHA of Aries at AM/PM twilight.
The latter twilight data could be used for setting up a Star
Finder for planning sights.
|To print the results, press Print and enter the number of days you wish computed (called number of rows) beyond the date entered and press OK. The data are formatted for standard letter size paper. The sun data are presented on two pages. A sample section of the print out is given below.
The times listed are Local Mean Times (LMT), same as given in the Nautical Almanac. These are best thought of as the GMT of the event as observed at Lon = 0°. To find local times, you need your Longitude (Lon) and Zone Description (ZD). Convert your Lon to time (using the Arc to Time Table) and then add to LMT for west longitudes or subtract for east.
GMT at your Lon = LMT + West Lon or LMT - East Lon
Local time = GMT - ZD