When was the constellation of Pegasus first sighted?
There is no real to that, because as long as humans have been looking at the night sky, all the constellations have been seen. Initially they were not given names and identified in the way we do now, having 88 identified constellations, but they could all be seen. Pegasus was a constellation listed in Ptolemy’s 48 constellations, which he did in the 1st century AD. You could use that as an answer, but it was only given a name around that time, not actually first sighted, which is your question.
