Sextant

Question 1

Name the parts of the sextant.

Answer 1

Telescope
Arc 
Index Arm
Index Mirror
1st Adjustment Screw
Horizon Mirror

Question 2

Define the 1st error of sextant.

Answer 2

Perpendicularity error:

When index mirror is not perpendicular to the plane of the instrument.

Question 3

Define the 2nd error of sextant.

Answer 3

Side error:

when the horrizon mirror is not perpendicular to the plane of hte instrument.

Question 4

Define the 3rd error of sextant.

Answer 4

Index error:

when the index and horrizon mirrors are not parrallel.

Question 5

How do you check the error of perpendicularity?

Answer 5

Move index arm to 1/3-1/2 arc.
Look down index arm toward arc.
Arc and acr’s reflection should join smoothly.
The first adjustment screw corrects.

Question 6

How do you check the side error?

Answer 6

Observe a star.
Set index arm to zero.
If the start appears at two images side-by-side then we have error.
The second adjustment screw corrects.

Question 7

How do you check the index error/parrallelism?

Answer 7

Observe a star.
Set index arm to zero.
If the spart appears at two images one on top, one below then we have error.
The third adjustment screw corrects.