In high latitudes, celestial observations...

In high latitudes, celestial observations...

Question 1 of 2707066636ee928f7522a1c519892

In high latitudes, celestial observations can be made over a horizon covered with pack ice by bringing the sun tangent to the ice and __________.

Question 1 of 27070

Q

In high latitudes, celestial observations can be made over a horizon covered with pack ice by bringing the sun tangent to the ice and __________.

🔍 Key Concepts

• Celestial navigation in ice-covered waters and how the visible "horizon" changes • Purpose and meaning of dip correction in sextant observations • Special tables in Bowditch Vol. II for non-standard horizons (ice, shore, etc.)

💭 Think About

• Ask yourself: when the sea horizon is blocked by pack ice, what is effectively becoming your new horizon, and how does that affect the way you correct your sextant altitude? • Think about whether semidiameter has anything to do with the horizon itself, or only with the apparent size/position of the Sun’s limb. • Consider which correction (or table) is specifically designed to adjust for an artificial or raised horizon, such as ice, a shoreline, or other obstructions.

✅ Before You Answer

• Make sure you are clear on what dip correction actually corrects for (height of eye above the true sea horizon). • Check in your mental picture of Bowditch whether there is a special dip table for unusual horizons (like ice or shore), and how it’s labeled. • Verify whether doubling the semidiameter or adding a fixed angle (like 30°) has any recognized role in standard sight reduction procedures for a Sun sight over an obstructed horizon.