Ah, I see! I should check the EV levels the next time I meter in these kinds of situations. However, I do know for a fact that I have successfully metered in situations where I have a stacked ND400 + ND8 and I'm metering at 30 sec (maximum on 5Kmk2 Aperture Priority mode) near the maximum aperture of whatever lens I have on there (F2.8~F4), so I believe it can handle a scene with a little less light than what you are describing.
So the Gossen LunaPro SBC, I see on the dial here for EVs down to -8... is that how dark the scene could be for this light meter to still meter accurately??
That's pretty amazing....
Yes, the LunaPro is the meter to use if you need to take a picture of a black cat in a coal mine, at night, under the new moon.