Move the Astrolabe to Cities and Planes

[Iceborn]

It's rather strange that the Astrolabe is in surface, while all the planes are actually in Cities and Planes.
It generates a strange friction if you want to explore more than one plane in a single run (as most will rather do), as you have to jump servers back and forth a few times.

And knowing how annoying server-jumping can be for casters who rely on their magic firsthand, having to pause repeatedly to rest as the jump would make most of the spells disappear and reappear to disappear again, I think that server-jumping should be kept to a minimum.

Amongst other reasons, like having to reform party, the usage of other per-rest abilities like animal companions, and generally feeling like a bump in what would be a smooth ride - or if the "bump" is kept intentionally, perhaps there are other ways to display this that are less mechanically annoying.