There has been some mention that the regs have no requirement for a visible horizon, a sad but true fact. But I seem to recall that I've seen something in a flight manual that requires some sort of light, "sufficient celestial illumination" I think. Now what this means is porberbly up to the person reading it, but I would be inclined to say ground lights, moon or stars. Something like the ammount of light you get even on an overcast dark night in the Sydney basin......... Being a flight manual requirement would mean it needs to be complied with for NVFR.
Any thoughts?????
cjam, not really sure about the somatographic effect, I doubt anything I can fly will accelerate fast enough for it to occur, or as I look outside, this could prevent it from happening.