Astrometry, Morphology, and Polarimetry of Comet Donati in 1858

Abstract

We present unpublished observations of Comet Donati 1858 V recently recovered in an old storage facility at the University Observatory in Oslo. Carefully-made drawings reveal temporal changes in the appearance of this comet. Fine structures in the tail were noted, some of which were short lived. Envelopes in the comet's head, apparently due to outgassing from the nucleus, were monitored over several days. Astrometric positions of the comet's head derived by various combinations of telescopes and micrometers reveal a standard deviation of ± 6". Visual polarimetry of the coma and tail revealed polarized light and determined that the polarization plane contained the comet and the Sun. Thus the polarized light from the comet was reflected sunlight. The observations are discussed in relation to contemporary publications.

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