sry nice idea, BUT:if you're willing to help me disprove it. I've added a second hypothesis.
Added a bit to it. I mean with the distances understood and what the angle means. It may allow us to figure out how far the long vertical wall is pointing at. I reckon It's pointing at another ruin somewhere.
I chcked the distances (triangulating from GALMAP) I get XR-H d11-102 -> Maia around 558 Ly and Centar of CalNeb -> 1107Ly - thats a ratio of nearly 1:2.
Transposed the ration in Log(10) its CalNeb 3.04, Maia 2.75 - makes 3.04/2,75= 1.1054
If U measure the lenght of the triangles sides then log(10) U get a ratio of 1.018 , so neither in absolute numbers nor in log() the length of the triangle axis can represent Pleiades/CalNeb