The utilization of optical alignment instrumentation in the assembly of certain large telescopes provides a convenient means for installing and calibrating these massive systems in the observatory. An experiment was performed during the factory acceptance test of a 1.22 m (48 in.) aperture Cassegrain to determine the accuracy which might be realized in practice. Scatterplate-interferometry and Hartmann tests were used with a 1.24 m (49 in.) optical flat to quantify laboratory performance. The results were impressive. The telescope alignment not only met the one-quarter wavelength peak-to-peak specification but also demonstrated that this type of calibration procedure can be performed on site, requiring a minimum of time, equipment and operator experience.