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With the demise of many commonly used Kodak Spectroscopic Plates attention has been directed toward alternative Kodak photographic materials for astronomical applications. Estar-based Kodak Type 4415 Tech Pan film is an attractive product owing to its very fine grain, ease of hypersensitization, excellent storage potential after hypering, and cost one tenth that of plates.
We have endeavored to compare the relative astrometric precision of 4415 film and IIIaF plates. As nearly identical conditions as possible were maintained at each stage of the comparisons. Both film and plate were exposed in contact with the same GG495 filter, alternating film/plate exposures to approximately same limiting magnitude, and minimizing hour angle differences. Exposures from each night were developed in one darkroom session. The photographs were measured with our PDS 1010GM, the film emulsion side up held flat by the plate emulsion side down.
Three film/plate pairs from the McCormick refractor and five film/plate pairs with the Fan 1 m reflector were used with ten stars in each comparison. We found standard errors for a single position to be $\pm 0.76 \mu$m for the 4415 film and $\pm 0.21 \mu$m for the IIIa-F glass plates. Further long-term comparisons are planned.
This work is supported by the National Science Foundation and the Estate of Leander J. McCormick
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