Tea Box Pinhole Camera Experiment

Today 2009-09-09 was the first day of university although I don't start teaching till tomorrow afternoon.
In preparation for another course I'll be teaching, University 201, I built a small pinhole camera out of a wooden tea box.  I took it into the darkroom in the SUB loaded it and went out around the building for 3 exposures and 1 over at the Clearihue clock tower. 
Using the data from a pinhole photography book I have, I calculated the f/stop and pinhole size I needed for the focal length of this camera.
Nothing is machine precise, but I think it was established pretty good.
Focal Length:  ~80mm; Needle #13 for a 0.30mm diametre pin-hole; which gives close to an f/stop of 242.
Using photo paper I calculated based on the given in another book, an ISO of 4.
Today's lighting conditions were cloudy with rain for all exposures.
Exposure #1:  ~3 min. ... too light
Exposure #2:    9 min. ... best of the test shots
Exposure #3:  10 min. ... a little too light, not sure why, maybe because of the angle, but still produced an image.
Exposure #4:   9 min. ... Clearihue Clock Tower w/ puddle of water reflection, paper curved over in the camera, just to see what effect I'd get.  Didn't produce a satisfactory result.

Conclusion:  Cloudy w/ rain ... f/242 @ 9 minutes. (+/-)

I noticed the images all had jagged edges, I assume this is because I sanded the pinhole too roughly and damaged it.  I also noticed a lattice design across the image, so I changed the pinhole this evening to a smooth thin sheet and sanded ever so lightly.  Hopefully this will produce better results, but for now here is a shot looking east from the SUB entrance towards the bookstore.  Despite the loneliness of the image, there were quite a few people walking about campus today.