ATP-3-09-02 Field Artillery Survey Download
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Chapter 7 7-16 ATP 3-09.02 16 February 2016 7-40. The following method can be used to orient the world star chart in the Northern Hemisphere. Determine the LST of observation from Figure 7-12. Enter the table with the closest date of observation. From the date, move to the right and stop in the column of the closest hour of observation. Extract the LST from the hour column. Locate the celestial equator. Subtract the observer's latitude from 90°. The result is the distance above the horizon to the celestial equator. Face south, and determine the position of the celestial equator. Remember, at arms length, a finger width is 2°, 1 hand width is 10°, and 1 hand span is 20°. Hold the world star chart with the word North on top. Locate the graduation at the top the chart that represents the LST. Face south, and align the LST graduation just below the celestial equator along the observer's meridian. The world star chart is now oriented with the stars in the sky. 7-41. The following method can be used to orient the world star chart in the Southern Hemisphere. Determine the LST from figure 7-12. Locate the celestial equator. This is done the same as in the Northern Hemisphere except the observer must face north and count up from the horizon to locate the celestial equator. Hold the world star chart with the word South at the top. Locate the graduation at the top of the chart that represents the LST. Face north, and align the LST graduation just below the celestial equator along the observer's meridian. 7-42. To aid the observer, highlight the 30° N and 30° S lines on the star chart. Also highlight the 0° line, which is the celestial equator. The strip of sky as outlined by the 30° N and 30° S lines will contain the brightest stars (seen at any one time). Keep in mind that the strip of sky being looked at is about 6 hours either side of the LST. Figure 7-12. Determine the local sidereal time (LST)