Celestial Navigation · Sextant Corrections — Index Error
Index error of a sextant is determined by:
- AReading the chronometer
- BLooking up the declination
- CMeasuring height of eye
- DSetting the instrument to zero and observing the horizon (or a body), noting the offset✓ Correct
Explanation
Index error is found by bringing the direct and reflected horizon into coincidence with the index near zero; the residual reading is the index correction (IC). It is 'on the arc' (subtractive) or 'off the arc' (additive).
Authority: Bowditch (Pub. No. 9), sextant adjustments
Practice the full Celestial Navigation bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Celestial Navigation questions
- Sextant Corrections — Index Error
Your sextant has an index error of 2.5' 'on the arc.' How is it applied to the sextant altitude?
- Time
The Nautical Almanac tabulates the positions of celestial bodies against which time standard?
- Time
A vessel in west longitude has a zone description of +5. To convert zone time to UT you must:
- Coordinates
How is the GHA of a star obtained from the Nautical Almanac?
- Coordinates
Sidereal Hour Angle (SHA) is best defined as:
- Coordinates
Declination of a celestial body is the celestial equivalent of: