AUTOMATED MICRODENSITOMETER FOR DIGITIZING ASTRONOMICAL PLATES.

Abstract

A precision microdensitometer has been built under control of an IBM S/1 time-sharing computer system. The instrument's spatial resolution is better than 20 mu m. A raster scan of an area of 10 multiplied by 10mm**2 (500 multiplied by 500 raster points) takes 255 minutes. The reproducibility is excellent and the stability is good over a period of 30 hours, which is significantly longer than the time required for most scans. The intrinsic accuracy of the instrument was tested using Kodak standard filters, and it was found to be better than 3%. A 'comparative' accuracy was tested measuring astronomical plates of galaxies for which absolute photoelectric photometry data were available. The results showed an accuracy excellent for astronomical applications.