Actually I was mainly referring to the non-map celestial artworks
Which are also on display in this exhibit and samples of which are online
at the Web site.
I agree that trying to use those old atlases to find celestial objects would
be quite a challenge, though that could be interesting in itself, to see
what earlier astronomers had to contend with, assuming they considered
such charts a problem rather than just an everyday (or night) part of
their job.