Which is TRUE for a sextant having an index...

Question 1 of 2707066636ee928f7522a1c51a3e9

Which is TRUE for a sextant having an index error that is "on the arc"?

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Question 1 of 27070

Q

Which is TRUE for a sextant having an index error that is "on the arc"?

🔍 Key Concepts

• Meaning of sextant index error and how it is read on the drum/arc • Difference between index error "on the arc" vs "off the arc" • How index error sign (on vs off) affects the correction you apply to your observed altitude

💭 Think About

• When you bring the direct and reflected horizons together with the sextant set at 0°, where does the vernier or micrometer line up on the arc if the error is "on the arc"? • If the sextant reading is greater or less than the true angle, do you need to add or subtract a correction to get the correct observed altitude? • Think about whether "on the arc" means your sextant is reading too high or too low compared to reality, and how that changes the sign of the index correction.

✅ Before You Answer

• Be clear on the physical definition of index error and how it is detected using the horizon method or artificial horizon • Know which sign (positive or negative) we assign to index error when it is "on the arc" in standard sight reduction forms and tables • Verify whether an "on the arc" reading requires you to add or subtract the index correction to obtain the true observed altitude