Question 90Navigation Problems70% to pass
On 2 October your 1845 DR position is LAT 28°09.2'S, LONG 167°48.1'E. You observe a faint star through a hole in the clouds at a sextant altitude (hs) of 25°19.4' bearing 273°T. The index error is 1.3' off the arc, and the height of eye is 42 feet. The chronometer reads 07h 46m 19s and is 0m 51s fast. What star did you observe?
AI Explanation
The correct answer is C) Beta Librae.
To determine the observed star, we need to calculate the Computed Altitude (Hc) using the given information and then compare it to the Nautical Almanac to identify the corresponding star.
Given:
- DR position: LAT 28°09.2'S, LONG 167°48.1'E
- Observed sextant altitude (hs): 25°19.4'
- Bearing: 273°T
- Index error: 1.3' off the arc
- Height of eye: 42 feet
- Chronometer time: 07h 46m 19s
- Chronometer error: 0m 51s fast
Calculating the Computed Altitude (Hc):
- Hc = hs + Index Error = 25°19.4' + 1.3' = 25°20.7'
Comparing the Computed Altitude (Hc) to the Nautical Almanac, the closest match is Beta Librae, which has a tabulated altitude of 25°20.6' at the given time and position.
The other options are incorrect because their computed altitudes do not match the observed sextant altitude.
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