柯达天文底片103a-O和IIa-O的性能变化及其对比研究

THE CHANGE OF AND COMPARISON BETWEEN THE PROPERTIES OF KODAK 103a-O AND IIa-O

美国柯达公司生产的天文底片103a-O和IIa-O是广泛使用了几十年的老牌品种.它们牌号不改,性能却多次变化,特别是IIa-O,然而当代世界上的天文用户们并未注意到这些变化.为此,本文重新把这些牌号未改但性能已改的底片做了感光学对比研究. 对我们比较的底片,未敏化使用时,IIa-O(批号HD1A6)比103a-O(批号HD215)速度稍快;颗粒却较细;特性曲线较平坦;输出信噪比和探测量子效率差不多.综合看,现在的IIa-O性能倒是比现在的103a-O更接近五十年代的103a-O.但经过气体敏化,103a-O的感光学性能仍然稍微优于IIa-O.

It is well known that Kodak 103-a0 and Ha-0 are classical emulsions which have been used in astronomy for several decades. Since the fine grain emulsion IIIa-J was introduced they have become less used, especially 103a-O. As far as we know, only a few astronomers still use 103a-O in Western countries amounng them A. G. Smith used it most, mainly in the fidst class detection (with high input signaI to noise ratio). The obvious examples are U. K. and ESO Eehmidt where the 103a-O is replaced by IIa-O completely. Unfortunately, the only quantitative comparison between 103a-O and IIa-O we have ever seen was made by Sire in Western countries, but she only compared the speed. We heard from private communications that the U. K. Schmidt Unit and ESO Schmidt made the decision according to the previous imprelsion only. While comparing the Kodak plates with the ORWO plates, the Czech astronomer Zichova gave the fog, speed, and (S/N) out of 103a-O and IIa-O (His purpose was not comparing 103a-O with IIa-O so his results were plotted in two separate figures). How ver, from his results it can be seen that the 103a-O is much more better than IIa-O. We have been using 103a-O and IIa-O fo more than 30 years in China. During this long period, both the properties of 103a-O and IIa-O have been changed several times, but only a few people have noticed the change including Reid et al. In fact, the so called classical emulsions only keep their original names constant. In 1950's, the σ_D of 103a-O is higher than that of IIa-O, the contrast of 103a-O is lower than that of IIa-O, the speed of 103a-O is faster than that of IIa-O. ……………… In 1980's, the σ_D is the same, i. e. 103a-O's σ_D is higher than that of IIa-O, but, the contrast of 103a-O is higher than that of IIa-O, the speed of 103a-O is similar to that of IIa-O. The (S/N) out=0.4343 γ/σ_D, though the σ_D of IIa-O is lower, its γ is lower too, so the (S/N) out of IIa-O is not necessary better than that of 103a-O 1 For this reason we have done the sensitometric comparisons between 103a-O and IIa-O as though they were new type emulsions. The results for the plates we checked (103a-O HD1A6; IIa-O HD215) are: 1. For untreated plates, IIa-O is a little faster than 103a-O, to some extent, the present IIa-O is more similar than the present 103a-O to the old 103a-O. 2. After hypersensitization, the property of the present 103a-O is still a little better than that of the present IIa-O.