On 24 March your vessel is enroute from Cadiz to Norfolk. Evening twilight will occur at 1830 zone time and your vessel's DR position will be LAT 35°06' N, LONG 60°48' W. Considering their azimuth, altitude, and magnitude, which group of stars is best suited for plotting a star fix at star time?

Question

On 24 March your vessel is enroute from Cadiz to Norfolk. Evening twilight will occur at 1830 zone time and your vessel's DR position will be LAT 35&deg;06' N, LONG 60&deg;48' W. Considering their azimuth, altitude, and magnitude, which group of stars is best suited for plotting a star fix at star time?

Accepted Answer

Option C: Sirius, Dubhe, Mirfak. Selecting stars for a fix requires a wide spread in azimuth to minimize the geometric dilution of precision. Bowditch dictates choosing stars with altitudes between 15° and 75° to avoid refraction errors and zenith distance inaccuracies. Sirius, Dubhe, and Mirfak provide the optimal distribution of azimuths and altitudes for this latitude.