How to check perpendicularity error of sextant ?
- Remove telescope
- Turn away the shades
- Set index arm about the middle of arc
- look into mirror so the true arc is visible and reflected arc seen in mirror
- if true and reflected arcs are not in a straight line error is present.
CORRECTION:-
- To remove perpendicularity error makes adjustment the first adjustment until true and reflected arcs are appear in a straight line.
How to check side error of sextant ?
- Remove telescope
- Turn away the shades
- Set index arm and micrometer exactly at zero.
- hold the sextant horizontally and look through the horizon mirror at horizon.
- If true and reflected arcs are not in a straight line error is present.
- Or hold sextant in vertical position and look directly 2nd magnitude star through telescope.
- If true and reflected images pass to the side by side error is present.
CORRECTION:-
- To remove error makes adjustment the second adjustment until true and reflected horizon or image of star are appear in a straight line.
How to check index error of sextant?
- Set index arm and micrometer exactly at zero.
- hold sextant vertically and look through the telescope and horizon mirror at horizon or 2nd magnitude star. If true and reflected horizon is not in a straight line then there is index error .to find index error adjust micrometer until they appear in a straight line.
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