I was finally able to download the STL files for a six bladed iris.
Note the direction of leaf opening.

There is also a different design with 4 leaves that open like trimned sphere caps on a sphere, in the opposite directions. (The hinge pins are on opposite side of the leaf.) For six leaves, the sphere opening size would be constrained by the hinge pins. 360 degrees ÷ 6 = 60 degree pin spacing. The corresponding arc length, plus pin&support radius determines the arc Length to the north pole of the dome.

A node with all leaves moving together might be possible?

- Brian