Ron:

I wrote the chief counsel's office about fifteen years ago on this
issue of logging "black hole time" after a long dispute about it on
AVSIG.
They sent me a copy of the above - supporting my position that the
criterion was "solely by reference to instruments" as opposed to "IMC"
for the logging of instrument time.

Reminds me of a time flying VFR over the top at night and the
controller asking my flight visibility. I said about 250,000 miles.
After the silence, I said that all I could see was the moon.