On 6 August your 1552 zone time DR position is LAT 24°26.0'S, LONG 73°19.0'E. At that time, you observe the Sun bearing 302°psc. The chronometer reads 10h 55m 07s, and the chronometer error is 02m 38s fast. The variation is 6°E. What is the deviation of the standard magnetic compass?
• Conversion of chronometer time to zone time using the given chronometer error and zone description for your DR longitude • Finding the Sun's true bearing at the given time and position from sight reduction (L, Dec, GHA, LHA, Hc/Z)**, then relating that to compass and magnetic bearings • Applying variation and deviation relationships: True, Magnetic, Compass (T–V–M–D–C) with correct algebraic signs (East/West)
• First, determine the exact UTC/GMT of the sight from the chronometer reading and error. Then convert to GHA/Dec of the Sun for that date and time and work out the Sun's true azimuth (Zn) at your DR position. • Compare the calculated true bearing of the Sun with the compass bearing (psc) observed. Use the T–V–M–D–C relationship to step from true to magnetic, then to compass, keeping careful track of East/West signs. • Think about whether a compass reading higher or lower than true (after applying variation) corresponds to East or West deviation. Set up a small example bearing line if needed to visualize this.
• Confirm the sign and application of the chronometer error (fast vs slow) when finding the actual Greenwich time. • Check that you've applied 6°E variation at the correct step (between True and Magnetic) and with the correct sign convention. • Before choosing an answer, verify whether your computed compass is east or west of magnetic, and then match that with the appropriate numerical value in the choices.
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