You observe the planet Jupiter at a sextant...

Question 1 of 2707066636eea28f7522a1c51b415

You observe the planet Jupiter at a sextant altitude (hs) of 66° 27.6' on 26 May. The index error is 5.2' on the arc. The height of eye is 52 feet. What is the observed altitude (Ho)?

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Question 1 of 27070

You observe the planet Jupiter at a sextant altitude (hs) of 66° 27.6' on 26 May. The index error is 5.2' on the arc. The height of eye is 52 feet. What is the observed altitude (Ho)?

🔍 Key Concepts

• Index error (IE) correction: how to apply "on the arc" vs "off the arc" • Dip (height of eye) correction: why it is always subtracted from hs • Using the Nautical Almanac altitude correction tables for planets to go from apparent altitude (Ha) to observed altitude (Ho)

💭 Think About

• First, convert the sextant altitude (hs) to apparent altitude (Ha) by correctly applying the index error and dip. Think carefully about the sign of each correction. • Next, think about what kind of body Jupiter is considered for sight reduction tables and what standard correction you would expect (roughly) at an altitude around 66°. Should it make Ho slightly larger or smaller than Ha? • Compare your step‑by‑step corrected value with the choices and see which one is consistent with both the direction and typical size (in minutes) of the total corrections.

✅ Before You Answer

• Be sure you know that "on the arc" index error is subtracted from hs, and "off the arc" index error is added. • Confirm the dip correction for a height of eye of 52 feet from the dip table (it should be a little over 6 minutes). • After applying IE and dip, verify that your planet correction from the Nautical Almanac is of a reasonable magnitude for that altitude (on the order of a few minutes, not tens of minutes).