Lumix G3 shooting thru Telescope Exposure Issue

I put on a little legacy 28mm Canon with an adapter because I have no micro 4/3 lenses right now, as a test because my scope shots are dark, and exposure is right, the photos are fine.

I have been shooting through an apochromatic refractor with adapters, and getting great shots... well, good enough to make me smile.

It's an overcast day in Seattle. I just got an appropriate quick release plate for this Gimbal head and couldn't wait to get out on the deck to take some photos.

Suddenly, everything is dark. I have NO idea what's up. I can pump ISO through the roof. I can slow the shutter speed to mollasses, all to no avail. Everything is coming out dark through the scope today. Again, with another lens, it's just fine.

Any thoughts? Other than the camera is smarter than I am. I already know that.