🔍 Key Concepts
• Sight reduction process for the Sun using an assumed position
• How to apply index error, height of eye, and chronometer error to get observed altitude (Ho) and correct time
• Relationship between LHA, latitude, declination, and azimuth (Zn) in the sight reduction tables or formulas
💭 Think About
• After correcting hs to get Ho, what information do you need from the Nautical Almanac at the exact UTC of the sight, and how do you get Local Hour Angle (LHA)?
• Given your latitude and the Sun’s declination, is the Sun north or south of you, and is it rising or getting higher? How does that affect whether Zn is to the east or west and roughly what quadrant it should lie in?
• When you compare Hc from the assumed position with Ho, what does the intercept direction tell you about whether your assumed longitude was to the east or west of your actual line of position, and how does that help confirm whether your Zn choice is reasonable?
✅ Before You Answer
• Be sure you’ve applied chronometer error correctly (remember it is slow) when converting to UTC and then to GHA
• Confirm you used the correct hemisphere sign for latitude (South) when entering tables or formulas
• Before choosing, check if your computed Zn quadrant (NE, SE, SW, NW) matches the time of day and the vessel’s approximate position in the Indian Ocean in mid-November