A technique using a laser to align the parallelism of a nest of rotational axes or surfaces 10 metres apart to within one-half arc minute will be described. The parallelism of rotational axes, 10 centimetres apart, of two cylinders can be aligned and measured with standard metrological instrumentation. The parallelism can also be aligned and measured with optical instrumentation, such as plane mirrors, an auto-collimator, or a telescope. When the sizes of the cylinders are enlarged and the separation is increased 100 fold, these approaches are impracticable because an auto-collimator of twice the aperture diameter and structure of the 200 inch telescope at Mount Palomar would be required.
Gerald F. Marshall,
Clifford L. Taylor,
"Laser Alignment Of Parallel Mechanical Axes 10 Metres Apart", Proc. SPIE 0369, Max Born Centenary Conf, (16 June 1983); doi: 10.1117/12.934370; https://doi.org/10.1117/12.934370