Celestial Navigation · Sextant Corrections
Parallax in altitude is significant primarily for which body?
- APolaris
- BSirius
- CThe Moon✓ Correct
- DDistant stars in general
Explanation
Parallax (the difference between altitude seen from the surface versus Earth's center) is large only for the Moon — up to about 1° (61'). It is about 0.1' for the Sun and negligible for stars, which is why the Moon has its own altitude-correction tables.
Authority: Bowditch (Pub. No. 9)
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
In reducing a sextant altitude (Hs) to observed altitude (Ho), the corrections are applied in which order?
- Sextant Corrections
The dip correction for height of eye is:
- Sextant Corrections
If the index error of a sextant is 'on the arc,' the correction is:
- Sextant Corrections
Atmospheric refraction in an altitude observation is:
- Sextant Corrections
When the lower limb of the Sun is brought to the horizon, the semi-diameter correction is:
- Sextant Corrections
The observed altitude (Ho) is: