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How to Determine Star Time and Selected Stars Using
Pub 249 Vol I (Selected Stars)
Example
Determining star time and selected stars for morning or evening
observations is simple. The process involves finding the time of sunrise
for morning observation or sunset for evening observations. Then you
find the LHA of Aries for the time of star time and record the data for the
seven stars on a worksheet.
Rule: Add 30 minutes to the time of sunset to determine evening star
time, subtract 45 minutes from sunrise to determine morning star time.
Example: The ship is located at 36°14.0' N 069°14' W, the date is 01
Sep 91. The ship is on course 090°T and is keeping +5R time zone.
Discussion
Although there are other methods of determining which navigational stars
are available for observations, using Pub 249 is the most widely used
method. In step 10, you are directed to record the values for Hc (height
computed) and Zn (the azimuth angle, or the true direction to point the
sextant towards) on a worksheet. At the time of publication, there is NOT
a standard worksheet available for use. A recommended format is
supplied on page 11. Use a PC word processor to reproduce this
worksheet locally.
Use figure 6-5 on the following page along with the example OPNAV
form to find selected stars.
6-10
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