If you were doing this professionally you would, because lenses introduce distortions of various kinds - typically barrel or pincushion depending on the focal l

If you were doing this professionally you would, because lenses introduce distortions of various kinds - typically barrel or pincushion depending on the focal length and/or the lens. So any view of the sky is an approximation, and will introduce subtle errors that make it harder to pin down an exact location. They probably won't be huge areas, but this would be a harder problem if the time and longitude had to be exact with no existing guesses.