Other instrumental errors are

• Error due to eccentricity of the inner and outer axis
• Errors due to lack of coincidence between line of sight and optical axis
• Error due to eccentricity of vernier
• Error due to imperfect graduations on the horizontal scale;
• Vertical index error
• Vertical hair not being perpendicular to the horizontal axis
• Error due to defective tripod

All of these errors are mostly compensated and minimised by taking mean of the observations. In case of horizontal angles it is the mean of face length and face right condition and in case of vertical angles, it is the mean of telescope direct and reversed conditions.

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