On 26 May your vessel's 1906 zone time position is LAT 27° 16.0' N, LONG 24° 37.0' W. At that time, a sextant observation of the planet Jupiter was made. The sextant altitude is 63° 27.6', and the chronometer reads 09h 05m 16s. The index error is 5.2' on the arc, and the chronometer error is 01m 25s slow. Your height of eye is determined to be 52.6 feet. What is the (Zn) of this sight using the assumed position?
• Intercept (altitude) method for celestial navigation using an assumed position • Application of index correction (IC), dip, and other corrections to get observed altitude (Ho) • Determining Zn (true azimuth) of a planet from the assumed position, GHA, and Dec
• After you correct Hs to get Ho, think about whether the body is generally to the north or south and to the east or west of your position based on its GHA and Dec relative to your assumed latitude and longitude. • Consider how the Local Hour Angle (LHA) indicates whether the body is east or west of your meridian and what that does to the azimuth quadrant. • Check whether your latitude (north) combined with the planet’s declination (north or south) would place the body high in the northern or southern sky.
• Be sure you know how to choose the assumed latitude and longitude from the DR position and time. • Verify the sequence: Hs → Ha (after index correction and dip) → Ho (after additional corrections). • When you compute Zn (from the sight reduction table or calculator), confirm that its quadrant matches the general bearing (N/S and E/W) you expect from plotting the assumed position and the body’s GP.
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