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Noting that the extensive astrometric observations of the double cometWirtanen (C/1956 F1) made by E. Roemer have never been published, I replicatethe contents of a fortuitously discovered copy of her measurement records ofthe companion's offsets from the main mass in 1957-1959 and use with such databy others to refine the fragmentation solution. The sublimation-drivennongravitational acceleration is shown to essentially control the companion'smotion in the orbital plane. The fragmentation parameters derived by the authorin 1978 have now been improved and strong disagreement with the independentresults by Roemer is noted. The revised model is employed to predict thepositions of the companion on the plates exposed by Roemer on 25 September1960, which she reported to show the principal nucleus but not the companion.At my request, these plates have now been scanned and processed at the LowellObservatory, and the companion is found to be located at the predictedposition. The images of the main mass and the companion on one of the twoplates are displayed.

On Elusive Observations and a Sly Companion of Comet Wirtanen (C/1956 F1)