On 30 June at 0630 zone time, morning stars were observed, and the vessel's position was determined to be LAT 25° 15.0' S, LONG 175° 36.0' E. Your vessel is steaming at 16.0 knots on a course of 302° T. A sextant observation of the Sun's lower limb is made at 1015 zone time. The chronometer reads 10h 14m 38s, and the sextant altitude is 32° 07.9'. The index error is 4.5' on the arc, and the chronometer error is 01m 25s slow. Your height of eye on the bridge is 58.0 feet. What is the azimuth (Zn) of this sight using the assumed position?
• Run the DR position forward from the star-fix time to the sun sight time using course and speed before setting up the sight-reduction triangle • Use the correct LHA (Local Hour Angle) and the signs of latitude and declination to determine the correct azimuth quadrant • Remember how the Zn quadrants work in the southern hemisphere and for a morning sun (east of the meridian)
• From your star fix at 0630 to the sun sight at 1015, what is the run in time, distance, and DR position you should use as the assumed position for the sight? • Given your DR latitude (South) and the sun’s declination on 30 June, is the sun to the north or south of you, and is it east or west of your meridian at 1015 local time? • Once you have Z or Zn from the sight-reduction tables or calculator, which 90° quadrant must the true bearing fall into based on time of day, hemisphere, and whether the body is north/south of you?
• Verify you used the correct DR/assumed position at the time of the sun sight, not the earlier morning-star fix • Check that the LHA you used is between 0°–360° with the correct E/W convention for your sight-reduction method • Before choosing an answer, confirm that the Zn direction (NE, SE, SW, or NW) makes sense for a morning sun in latitude 25° S on 30 June at about 10:15 local time
No comments yet
Be the first to share your thoughts!