On 24 August your vessel is enroute from Perth, Australia, to Bombay, India. Evening twilight will occur at 1807 zone time and your vessel's DR position will be LAT 27°17.0' S, LONG 83°17.0' E. Considering their magnitude and location, what are the three stars best suited to observe for a fix at star time?

Correct Answer: Option A — Spica, Altair, Acrux

Selecting stars for a fix requires a spread in azimuth of approximately 120 degrees to minimize geometric dilution of precision. Spica, Altair, and Acrux provide optimal separation in both magnitude and bearing for a vessel at 27°S latitude during evening twilight, ensuring a robust and reliable celestial fix.