It is usually assumed that all copies of an edition of a star atlas are identical. This paper discusses variations within the Fortin-Flamsteed star atlas of 1776, in particular the alterations made to map 10, where the introduction of Taurus Poniatowski is the most apparent change. These alterations to the printing plates, together with various advertisements by the publishers and reviews in contemporary journals, enable a chronology of the introduction of a new constellation to be established.