🔍 Key Concepts

• Lunar observations (Moon sights) in celestial navigation • How Moon’s apparent size and shape change with phase and altitude • Which errors are biggest in practice versus mostly theoretical

💭 Think About

• Think about which option describes something that would consistently make it hard to take or use a Moon sight, not just a small computational correction • Ask yourself: Which of these problems would mainly affect the observation with the sextant, and which would mainly affect the mathematical reduction? • Consider your experience (or what you’ve read): When navigators talk about Moon sights being tricky, what practical issue do they most often complain about?

✅ Before You Answer

• Identify which choices deal with computational corrections (parallax, GHA, declination, augmentation) versus visual/observational difficulties • Recall that large, well-known corrections like horizontal parallax and augmentation are tabulated and routinely applied—are they usually considered a ‘major problem’ or just normal corrections? • Decide which option describes a difficulty that cannot be fully removed just by better tables or math, because it is inherent in what you see through the sextant