Step 1  
Identify the value of E◉ in the Nautical Almanac that immediately precedes the observation time.

​

Step 2  
Since E◉ is tabulated at two-hour intervals, the value at the desired time can be obtained by interpolation.

​

Step 3  
Add the observation time (UTC) to the value of E◉ obtained in Step 2 to determine the hour angle.

​

Step 4  
Since the hour angle is expressed in time units, convert it to angular degrees by multiplying by 15.

​

Step 5  
For declination, determine the value corresponding to the observation time.  
Apply the appropriate P.P. correction obtained from the right-hand column to derive the solar declination.

Calculation of the Meridian Passage Time of the Sun

Determine the meridian passage time on January 1 at longitude 140°E.

Step 1  
At meridian passage, the Local Apparent Time (LAT) of the Sun is always 12h00m00s.

Step 2  
Longitude time is obtained by dividing the longitude by 15.  
Add the longitude time for east longitude, and subtract it for west longitude.

Step 3  
Using this longitude correction, obtain the Greenwich Apparent Time (GAT).  
From this time, determine the corresponding value of E◉ from the Nautical Almanac.

Step 4  
Since E◉ is tabulated at even-hour intervals, the value at the desired time can be obtained by interpolation.

Step 5  
The equation of time is obtained by subtracting 12h00m00s from E◉.

Step 6  
Greenwich Mean Time (GMT) is obtained by applying the equation of time to GAT.  
(Note: the sign of the equation of time is reversed.)

Step 7
Local Mean Time (LMT) is obtained by applying the longitude correction or standard time correction.
For this correction, subtract in the case of east longitude and add in the case of west longitude.

Step 8  
An approximate meridian passage time M.P.(LMT) can also be obtained from the value labeled M.P. in the Sun column of the Nautical Almanac.

Correction of the Observed Altitude of the Sun