Worse, it looks like I have dust on my sensor

Why would a hub request a voltage it doesn't support? I assume the usb port should output 5v unless a different voltage is requested explicitly.

I think it's city lights reflected from a thin cloud.

I don't do astrophotography often, but that night the sky was surprisingly clear, so I had to take some pictures.

Thank you. Deepskystacker worked really well on another batch. I'll use different settings next time and will do the dark and bias frames.

You're right, here's a plane

Sure. Nikon d750 with Nikon AF 50mm f/1.8 D in this case I used 1/2 second exposures at f/4, ISO 3200. Around 25 raw frames, 3 of which were discarded during editing. Manually aligned them in photoshop, converted to a smart object, tried avg and max stack modes. This one is the max.

I tried 30 second exposures at first, but those were too blurry. 2-4 seconds works fine, but I'll keep experimenting

Yes, probably. You can see from the line where I removed a couple frames that were blurry, and at one point the camera filled its buffer and slowed down a bit

Sure