Uniformity of UKSTU Photographic Plates

Abstract

Most plates taken with the UK Schmidt Telescope are hypersensitized before use. The technique for the hyper-sensitization of IIIa-type emulsions has been described by Sim et al. (1976), and for the IV-N emulsion by Hartley and Tritton (1979). Photographic calibration is provided by two sensitometers, a seven-step linear array at the N-W corner and a 4 × 4 spot array in the S-E. During the calibration of this latter sensitometer (Dawe and Metcalfe 1981), which is a copy of a design by Schoening (1976), it became apparent that the sensitivity of the hypersensitized IIIa-emulsions in use was decreasing as a function of time in the plateholder.