Hi ghoot,
Yup - the POT command requires some calibration. If you use tight tolerance caps, the real problem will be the CDS cells - which vary pretty wildly (at least all the ones I've tried) and are going to need some 'tweaking' to get the Day/Night switching right in any circuit.
Ther used to be an "auto-calibrate" routine for the POT command in the PBP manual - but it may have not been included in the new manual.

QUOTE:
"Say if a value of 50 or so was enough to know it's dark, then I could just say anything greater than 50 is dark. Does this make sense?"
EndQUOTE

That's about what I did. The neat thing about the POT command is you can tell relative light intensity without using an ADC. Kind of interesting for logging info like "overcast", "bright night", etc.

BTW - when calibrating, you'd want the maximum resistance (CDS totally dark) to end up with a count at or near 255.