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El día 20 de abril de 2024, navegando con rumbo verdadero Rv=130°, y tras haber cruzado la línea del Trópico de Capricornio, a la hora de la meridiana observamos la altura instrumental del Sol (limbo inferior), obteniendo ai= 51°50,4´, y una declinación de +11°52,5´. El error de índice del sextante es de Ei= +0,6´, y la elevación del observador sobre el nivel del mar es de 7 metros. Se pide determinar la latitud observada en la que nos encontraremos en dicho momento.On 20 April 2024, sailing on Rv = 130° after crossing the Tropic of Capricorn, at meridian transit the Sun's lower-limb sextant altitude is ai = 51° 50.4', declination +11° 52.5', index error Ei = +0.6', and height of eye 7 m. Find the observed latitude.
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Correct answer: d) 26° 06.0' S.
Why it is correct
Correcting ai = 51º 50.4′ with Ei = +0.6′, dip for 7 m (−4.7′), and April lower-limb Sun correction (+15.2′) gives av = 52º 01.5′ and zenith distance z = 90º − 52º 01.5′ = 37º 58.5′ S. Since declination is 11º 52.5′ N, l = 37º 58.5′ S − 11º 52.5′ N = 26º 06.0′ S.
Why the others are not
- a) Adds z and d (37º 59′ + 11º 53′ = 49º 52′), forgetting they have opposite names.
- b) Gives the zenith distance z (37º 58′) without subtracting the declination.
- c) Gives the uncorrected zenith distance without subtracting declination.
How to work it out in the exam
- South of the Tropic of Capricorn the Sun bears north (z is South); with North d, subtract: l = z − d.
Where this question comes from
- Ministerio de Transportes (Madrid) · 2024 · Convocatoria de abril · CY Test 1 · question 11 Official paper · Official answer key
Pending instructor review. Machine translation, not reviewed.