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Sabiendo que el 18 de diciembre de 2020 se toma una altura instrumental del Sol de 35°45.7´, que el observador se encuentra a una altura de 2,4 metros sobre el nivel del mar y que el cero del tambor micrométrico del sextante queda a 0,2´ por debajo del cero del nonius, se pide calcular la altura verdadera del Sol.On 18 December 2020 the Sun's sextant altitude is 35° 45.7', height of eye is 2.4 m above sea level, and the zero of the micrometer drum lies 0.2' below the zero of the vernier. Calculate the Sun's true altitude.
Show the answer
Correct answer: b) 35° 57.8'
Why it is correct
With the drum zero 0.2′ below zero, the sextante reads high and the index correction is Ci = −0.2′, giving ao = 35º 45.5′. Subtracting dip for 2.4 m (−2.7′) leaves aap = 35º 42.8′, and adding the December Sun correction (+15.0′) gives av = 35º 57.8′.
Why the others are not
- a) Adds the dip of the horizon instead of subtracting it.
- c) Adds both the index correction and the dip of the horizon.
- d) Subtracts the Sun's semi-diameter instead of adding it for the lower limb.
How to work it out in the exam
- Dip is always negative (−2.7′); lower-limb Sun correction is always positive (+15.0′).
Where this question comes from
- Ministerio de Transportes (Madrid) · 2021 · Convocatoria de diciembre · CY Test 1 · question 12 Official paper · Official answer key
- Ministerio de Transportes (Madrid) · 2021 · Convocatoria de diciembre · CY Test 3 · question 11 Official paper · Official answer key
Pending instructor review. Machine translation, not reviewed.