Collimation

[Sarah]

The act of collimating; the adjustment of the line of thesights, as the axial line of the telescope of an instrument, into itsproper position relative to the other parts of the instrument. Errorof collimation, the deviation of the line collimation of anastronomical instrument from the position it ought to have withrespect to the axis of motion of the instrument.-- Line of collimation, the axial line of the telescope of anastronomical or geodetic instrument, or the line which passes throughthe optical center of the object glass and the intersection of thecross wires at its focus.