You observe the star Antares at a sextant...

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Question 1 of 2066636eea28f7522a1c51b417

You observe the star Antares at a sextant altitude (hs) of 38° 18.7' on 28 February. The index error is 2.4' on the arc. The height of eye is 40 feet (12.2 meters). What is the observed altitude (Ho)?

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Question 1 of 20

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🔍 Key Concepts

• Index error (on the arc vs off the arc) and how it changes the sextant reading • Dip correction for height of eye and how it affects the altitude • The sequence: hs → ha (apparent altitude) → Ho (observed altitude) for a star sight

💭 Think About

• First decide whether an index error that is on the arc should be added to or subtracted from the sextant altitude. What does "on the arc" tell you about the sextant reading? • Think about dip: does increasing the height of eye make the uncorrected sextant altitude too big or too small? So should the dip correction be added or subtracted? • After applying both index error and dip, compare how far your final Ho is from the original hs. Should it end up slightly higher or slightly lower?

✅ Before You Answer

• Be clear on the sign of the index correction for "2.4' on the arc" before doing any math • Use the correct dip correction for a height of eye of 40 ft (approximately 12.2 m) and apply it with the correct sign • After all corrections, ensure your final Ho matches one of the listed options and is reasonable relative to the original sextant altitude

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