Use of Kodak Tech-Pan Film at the UKSTU

Kodak Technical Pan (Tech Pan) emulsion is an extremely fine grained, high resolution, pan chromatic negative film with extended red sensitivity. It has been produced under this name since about 1980 (Kodak P-255, 1981) and is available on Kodak’s Estar base in a number of thicknesses and sizes. The thick **base Tech Pan is designated 4415 and has been used with great success by the amateur astronomical community for many years (e.g. Martys 1991). Its astronomical potential was recognised early by Everhart (1981). However, tests at professional telescopes (e.g. West et al. 1981) and early sensitometer tests at the UK Schmidt Telescope (UKST) in 1981 and 1987 were discontinued when the glass and film samples did not respond well to normal hypersensitisation techniques. These and other difficulties led to a lack of interest among the professional astronomical community until quite recently (Russell et al. 1992; Parker & Malin 1992). The first successful use of 14 x 14 inch hypered Tech-Pan 4415 film in the UKST was in March 1991. Films were obtained which exhibited excellent image quality and resolution. Furthermore, in good seeing these appeared to be about 1 magnitude deeper than the equivalent IIIa-F emulsion on glass but with considerably lower grain noise. This result was achieved because two main problems associated with Tech-Pan and film use in the UKST have been resolved. These were: 1 obtaining Tech-Pan film with long exposure speed sufficient for deep astronomical photography (i.e. reduction of low intenstiy reciprocity failure); 2 overcoming the practical difficulties of mounting large-format flexible film at the UKST’s curved focal surface