The Line of Colimation is what?

• A. The actual physical line of sight.
• B. The imaginary line at the elevation of the telescope's optical axis.
• C. The horizontal plane through the instrument.
• D. The line along the base of the tripod.

Answer: (B)

Line of collimation is the imaginary line that runs along the telescope's optical axis—the straight path through the center of the objective and eyepiece. It represents the direction the instrument is truly aimed, extending with the same elevation as the optical axis. When the instrument is properly collimated, the line of sight to a target aligns with this axis; any misalignment introduces a collimation error that can skew angle measurements. It isn’t a visible physical line, nor a horizontal plane through the instrument, nor the line along the tripod base.