On 29 June you observe the star Achernar at...

Question 1 of 2707066636eea28f7522a1c51addf

On 29 June you observe the star Achernar at a sextant altitude (Hs) of 54° 18.9'. The index error is 4.7' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

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Question 1 of 27070

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On 29 June you observe the star Achernar at a sextant altitude (Hs) of 54° 18.9'. The index error is 4.7' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

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🔍 Key Concepts

• How to correct sextant altitude (Hs) to get observed altitude (Ho) • The sign and meaning of index error off the arc • Effect of height of eye on the dip correction and whether it is added or subtracted

💭 Think About

• Start from Hs and apply the index correction: with index error off the arc, should you add or subtract to get Ha (apparent altitude)? • Next, think about dip: does height of eye make the horizon appear higher or lower, and therefore is dip correction applied as a minus or plus? • After index correction and dip, consider whether any additional corrections (like refraction) are needed to reach Ho for a star on this type of exam problem.

✅ Before You Answer

• Be sure you know the correct sign convention for index error when it is stated as "off the arc" • Confirm the direction of dip correction for a real horizon (height of eye 58 feet) • Track every step clearly: Hs → Ha (after index) → Ho (after dip and any other required corrections) and compare your numerical result with the choices.