Local Noon by Equal Altitudes

If you must know the exact time of local noon and have a watch, then a little before noon, measure the altitude of the sun. Note the time from your watch. Wait until the sun is at exactly the same altitude after local noon and note the time (see Figure 10.2). Local noon is halfway between the two times.

If you have a watch then you can find the exact time of local noon. Note the time when the sun rises and again when it sets. Local noon is exactly halfway between the two times. If you have made some easting or westing you will have to make allowance for distance sailed east or west.

It does not matter if your watch is wrong. It is the time difference that is important. You can still find local noon on the first day and put your watch right at noon on day two.

Alternatively, in the morning note the time and altitude of Sunrise 1 and Sunrise 2. Then in the evening when the sun is setting Sunset 1 is the time when the sun's altitude is equal to Sunrise 2. Local noon is halfway between these two times. It is the same for Sunrise 1 and Sunset 2. If your sums give different times for local noon from different sunrises and sunsets then take an average.

10.2 Finding Local Noon

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