McPherson Spectrogram-Measuring Microscope

This is a very rare item. It is a McPherson measuring microscope designed for critical measurement of spectral line separation. Plates can be scanned over an area of 250mm by 100mm. The measurement in the X-direction is via a scale on the front of the instrument graduated in single mm�s. Resolution is increased to 1 micron via a vernier on the 150mm diameter drum dial for the leadscrew. The leadscrew itself has a diameter of 25mm, with a pitch of 1mm.