Reply: how to determine Cn axes
There exists a program recognizing molecular orbital symmetries
which can determine the principal axes of an arbitrary molecule, too.
This is the program No. 484, available at QCPE (Quantum Chemistry
You can find the description of this program in the QCPE Bulletin
4(4), 107(1984) and Comp. & Chem. 9, 179(1985).
The program is well documented and very simple to use.
For determination the molecular symmetry you have to write into the
input file the cartesian coordinates of the molecule.