They are defined on the coordinate grid of 1875; precession has shifted and rotated them since then, and a map for the present epoch must account for that. In addition to the vertices, you may need to interpolate a few points along the edges.
Davenhall and Leggett 1989 provide boundary coordinates for epochs 1875 and 2000.
For determining which constellation contains a given point, Roman 1987 provides regions and lookup code.
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