Bolton measuring machines

The AAO has two Bolton measuring machines. Note that these are digitised to 10m so the limiting accuracy on a Schmidt plate is not really adequate for fibre work at the AAT Cassegrain focus, though AAT plates can be measured to sufficient accuracy for this purpose.

At Epping
Built by John Bolton, this plate measuring engine was originally installed at the Parkes radio telescope. The design is based on a standard XY carriage, but uses a vidicon TV camera to view the plate at high magnification. The performance at low light levels and built-in illumination are particularly useful for astrometric measurements of the print copies of the Palomar sky survey.

A typical accuracy of 0.5" can routinely be obtained from sky survey plates using standard techniques to avoid backlash etc. The Bolton measuring machine is located in the sky survey room in the Massey building, along with a cookbook on how to prepare astrometric coordinates.

At Siding Spring
This machine is similar to the one at Epping. A special effects generator allows the images of two plates to be compared or superimposed, together with a fiducial marker for position measurement. The attainable accuracy is about 1" on sky survey plates.