After transliterating the coordinates seen in the last two episodes, I am safe enough to say that At Attin is in the vicinity of G'wenee and Dathomir, while At Aytuu should be vaguely in the vicinity of Batuu.
At Aytuu
Grid square: G-15
XYZ coordinates: -403.25, -593.33, (not visible)
At Attin
Grid square: N-6
XYZ coordinates: 285.91, 375.30, 019.82
The XYZ coordinates seems to be fitting with the grid location, if compared to the ones of other planets in the surroundings.
You can get an idea here: http://www.swgalaxymap.com/
I just updated the respective Wookiepedia.
Dathomir. I really hope that means we can expect the Nightsisters to make an appearance.
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