🔍 Key Concepts

• High altitude observations in celestial navigation and how they affect the geometry of lines of position (LOPs) • How sextant altitude corrections (index error, dip, semidiameter, parallax, refraction) depend on altitude • How the azimuth of a celestial body changes with time at different altitudes

💭 Think About

• Think about what actually changes when the observed altitude of a body is high rather than low: does it change the corrections you apply, or the usefulness of repeated sights? • Consider how quickly the bearing (azimuth) of a star or the Sun changes when it is high in the sky compared to when it is near the horizon—how does that affect your ability to get a good crossing angle between LOPs? • For each option, ask yourself: is this something that depends mainly on the body’s altitude, or is it something that is basically the same at all altitudes?

✅ Before You Answer

• Check which corrections (like semidiameter and parallax) are applied because of the body’s nature and distance, not mainly its observed altitude. • Verify which choice directly relates to getting more useful position lines from sights taken at different times. • Eliminate any option suggesting that you no longer need standard almanac data (like GHA and declination) just because the altitude is high.