Precision astrometry with SuperCOSMOS |
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Authors: | N C Hambly L Miller H T MacGillivray J T Herd & W A Cormack |
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Institution: | Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ,;Department of Computing and Electrical Engineering, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS |
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Abstract: | We describe the new, fast, high-precision microdensitometer SuperCOSMOS. Some aspects of hardware and software design that enable high-precision astrometry from photographic plates are explained. We show that the positioning repeatability of the measuring machine is less than 0.1 μ μ m standard error in either coordinate, and the absolute positional accuracy is about 0.15 μ m standard error. Furthermore, measurements of the same plate in different orientations show that the sampling errors are small (e.g. ∼ 0.2 μ m, rising to ∼ 1.0 μ m at the plate limit, for stellar images in a IIIaJ emulsion), thus allowing the extraction of relative positional information from Schmidt plates at accuracies less than 1 μ m. We demonstrate that SuperCOSMOS is capable of measuring the positions of bright stars (i.e. those more than ∼ 4 mag above the plate limit) to a precision ∼ 0.5 μ m with survey–grade photographic plates employing fine–grained emulsions. |
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Keywords: | methods: data analysis astrometry |
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