🔍 Key Concepts

• Intercept (altitude) sight process: Convert sextant altitude (Hs) to observed altitude (Ho) applying index, dip, and other corrections, then compare to computed altitude (Hc). • Time and GHA/LHA: Convert zone time to GMT using zone description, then apply chronometer error to get correct UTC, and from that determine GHA Aries and Venus and then Local Hour Angle (LHA) at the assumed position. • Zn determination: Use the assumed latitude, declination of Venus, and LHA to determine the true azimuth (Zn), paying attention to the correct quadrant (NE, SE, SW, NW).

💭 Think About

• First, think through how you convert the given zone time and chronometer reading into the exact UTC of the sight. What is the zone description for 143°E, and how does the chronometer error change the time? • Once you have the correct UTC, what tables or data do you need from the Nautical Almanac to find Venus’s GHA and declination at the sight time, and how do you combine that with the assumed longitude to get LHA? • When computing Zn, consider whether Venus should appear generally to the east or west of you at that local time and latitude. Which two answer choices correspond to roughly opposite directions, and which two are also opposite? Use that to eliminate impossible quadrants.

✅ Before You Answer

• Confirm you applied index correction correctly: "off the arc" means the correction is added to Hs; "on the arc" means it is subtracted. • Double-check the time conversion chain: zone time → GMT (UTC) → apply chronometer error → sight time; a sign mistake here will flip the body to the wrong side of the meridian and give a wrong Zn quadrant. • Before choosing, sketch a quick compass rose and estimate whether Venus at that local evening/morning time and latitude should be in the NE, SE, SW, or NW; verify that your computed Zn falls in a realistic quadrant.