How to find crab nebula

[glowjet]

In TLAO they reckon M1 was probably twice as bright 200 years ago, and dim as it is today Messier probably wouldn't have included it in his catalog.

I think you may have hit the nail on the head there, Charles Messier would undoubtedly have had very dark skies, but the lens in his scopes, mostly a 4.75 refractor would not have been to the quality and standards that glass objectives are to-day, his chief lens maker de Saron even lost his head over it, not through making bad optics, but being on the wrong side during the revolution