Sextant Error Identification and Correction

This video tutorial explains the errors associated with sextants, dividing them into non-correctable and correctable categories. Non-correctable errors include centering, prismatic, shade, graduation, collimation, and instrument errors. Correctable errors, such as perpendicularity, side error, and index error, are discussed with methods for correction. The tutorial provides detailed steps to adjust and correct these errors, ensuring accurate sextant readings.

What are the two main categories of sextant errors?

• Horizontal and Vertical

• Correctable and Non-Correctable

• Major and Minor

• Mechanical and Optical

Which error occurs when the pivot point of the index arm is misaligned?

• Shade Error

• Centering Error

• Collimation Error

• Prismatic Error

What is the main cause of graduation error in a sextant?

• Deflection of light rays

• Wearing of the cogs

• Inaccuracies in the scale graduations

• Misalignment of mirrors

How can you check for perpendicularity error in a sextant?

• By looking for continuous arcs in the index mirror

• By setting the index to zero

• By adjusting the micrometer drum

• By aligning the horizon mirror

Which screw should be adjusted to correct perpendicularity error?

• The one at the top of the mirror

• The one on the horizon mirror

• The one at the bottom of the mirror

• The one nearest the frame

What indicates the presence of side error in a sextant?

• A step in the horizon

• Separated real and reflected objects

• Misaligned index mirror

• Continuous arcs in the index mirror

What is the relationship between side error and index error?

• They are both non-correctable

• They are corrected independently

• They are unrelated

• They must be corrected together

How can residual index error be adjusted after correcting side error?

• By recalibrating the scale

• By tilting the sextant

• By using the micrometer drum

• By adjusting the horizon mirror

What should be done if the error is measured off the arc?

• Subtract it from all measurements

• Add it to all measurements

• Ignore it

• Recalibrate the sextant

What is the final step after eliminating all possible errors in a sextant?

• Recheck for non-correctable errors

• Start taking measurements

• Adjust the micrometer drum

• Recalibrate the instrument