Thanks, Sharon and Kelly.
This was shot using a circular fish eye, pointed exactly to the ceiling, freehand. I used PTGui to correct geometry; this resulted in an (almost) rectangular picture instead of a circular one (I cannot remember which transformation I used; I just tried several ones.) For this entry, I used a resized version and cropped a considerable amount from the left and right sides. As soon as I can find the originally sized version, I'll post a link to a bigger image.
Gerald
