🔍 Key Concepts

• Luminous range tables and visibility in navigation • How the magnitude scale works in astronomy (smaller number = brighter object) • What mariners mean by “first magnitude” stars on a clear night

💭 Think About

• Think about: when we casually talk about a bright “first magnitude star,” are we usually including only the very brightest stars, or a slightly wider group? • Compare the listed values (0.5, 1.0, 1.25, 1.5). Which of these seems like a reasonable upper limit for a group called “first magnitude” rather than “second magnitude”? • If a star has magnitude 1.4, would many navigation texts still call it first magnitude, or would they likely push it into the next class?

✅ Before You Answer

• Check how the magnitude scale is ordered: do smaller or larger numbers mean brighter? • Verify approximately what magnitude well‑known bright stars (like Sirius, Vega, Capella) have, and where the cutoff between first and second magnitude is usually placed in nav references. • Confirm which option best matches the idea: “first magnitude” = stars brighter than some threshold value.