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El 23 de junio de 2015 se ha tomado una altura instrumental del Sol de 43° 21.7´, el ojo del observador está a una altura de 14,2 metros sobre el agua, y el cero del tambor micrométrico del sextante queda a 0.2´sobre el cero del nonius. Se pide calcular la altura verdadera del Sol.On 23 June 2015 the Sun's sextant altitude is 43° 21.7', height of eye is 14.2 m above the water, and the zero of the micrometer drum lies 0.2' above the zero of the vernier. Calculate the Sun's true altitude.
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Correct answer: d) 43° 30.0'
Why it is correct
With Ci = −0.2′, dip for 14.2 m (−6.7′), and the June lower-limb Sun correction for 43º (+15.2′), the net correction is −0.2′ − 6.7′ + 15.2′ = +8.3′. Added to 43º 21.7′, that gives av = 43º 30.0′.
Why the others are not
- a) Forgets to subtract the 6.7′ dip of the horizon.
- b) Subtracts 2′ too much in the total correction.
- c) Misapplies the Sun's semi-diameter.
How to work it out in the exam
- For 14.2 m the dip is −1.775 × √14.2 = −6.7′.
Where this question comes from
- Ministerio de Transportes (Madrid) · 2019 · Convocatoria de junio · CY Test 1 · question 12 Official paper · Official answer key
- Ministerio de Transportes (Madrid) · 2019 · Convocatoria de junio · CY Test 2 · question 16 Official paper · Official answer key
Pending instructor review. Machine translation, not reviewed.