Graphics, Figures & Tables ⇒ Naming a path through a point

[topsquark]

Say I have a coordinate point (P) and I want to draw a circle through it.
\node [draw] at (0,0) [circle through={(P)}] {};

Can I name this path so I can refer to it later? (I don't know the coordinates of (P), I found it using "intersection" and I've recently discovered that if I find the x and y coordinates, the values can be too approximate to with well.)

Thanks!

-Dan