🔍 Key Concepts

• Celestial navigational triangle (spherical triangle on the celestial sphere) • The three corners (vertices): elevated pole, observer’s zenith, and celestial body • Relationship between sides (arcs) and angles in this triangle

💭 Think About

• First, list the three points that form the celestial navigational triangle. Which arcs (great-circle distances) naturally connect these three points? • Ask yourself: which of the options is normally treated as an angle at a vertex rather than the length of a side (an arc) between two points? • Think about standard sight reduction tables (e.g., HO 229/249): which three quantities form the sides used in the triangle solutions?

✅ Before You Answer

• Be clear on the definition of zenith distance and how it relates to observed altitude. • Recall what colatitude means in navigation and which two points it joins on the celestial sphere. • Verify whether codeclination is typically used as a named side in the standard navigational triangle, or appears instead in other contexts.