Donati first observed the comet on 2 June from the Florence Observatory: it was initially visible as a small nebula-like object of magnitude 7 near the "head" of Leo.

[4] The final observation was by William Mann, chief assistant at the Royal Observatory, Cape of Good Hope, who detected it as a faint nebulosity on March 4, 1859.

After a prior period of hysteria on the subject of comets, especially in Paris (caused partly by incorrect calculations by John Russell Hind which suggested that one would strike the Earth in June 1857) Donati's Comet went on to be the most-observed of the century due to its excellent visibility in dark skies for Northern Hemisphere viewers, particularly in Europe, and fine weather in September and October.

[13] Donati himself, a relatively obscure figure, was propelled to the status of an astronomical hero, and the comet helped cultivate a general enthusiasm for astronomy among the public.

[14] Donati's Comet appears as a streak and star in the early evening sky of a painting by William Dyce, Pegwell Bay, Kent – a Recollection of October 5th 1858.

[16] Abraham Lincoln, then a candidate for a seat in the U.S. Senate, sat up on the porch of his hotel in Jonesboro, Illinois, to see "Donti's Comet" on September 14, 1858, the night before the third of his historic debates with Stephen Douglas.

"[18] The influence of the comet, particularly in visual and design terms, was such that traces of its appearance can be found in magazine and commercial illustrations, household objects, children's books and other items up until the early years of the 20th century.