Hal,

It's a "passes=o" (orbital) which I have not used before.  Interestingly, different pixel resolutions (image horizontal and vertical sizes) give slightly different versions of his fractal.  I used Richard's Fractint for Windows beta 5 (not for general release;  now renamed Iterated Dynamics).

Even 1280x960 size images continue to evolve over time in a pleasing way.

I really like this parameter file.  If you run it and then go to the <p> screen, when you set the orbit delay to 10, the image starts to look vaguely like Rolf from the Muppet Show. Jonathan