Velvet - sorry if I appeared too critical but I am honestly shocked that the FAA have allowed this to happen, it seems utterly irresponsible not to impose some regulations or limits to prevent people frightening or killing themselves.
The Met Office in UK produce a light level prediction programme which might be useful but I suspect such a thing already exists within the US. Unfortunatley, although it makes allowances for differing levels of cloud cover, it can't make a go/nogo decision based on weather, it purely deals with starlight and moonlight.