I was out taking photos of the Milky Way as I do on most clear nights when bright flashes appeared in the sky

I am a photographer who spends most clear nights capturing the Milky Way. I have over a decade of experience of astrophotography and can easily identify passing satellites which are so numerous these days it’s hard to get a good photo without them. I was taking a long exposure of roughly 13 seconds, and at about 2 or 3 seconds into the exposure a bright flash appeared within the frame, about 10 seconds later it flashed again. Upon closer inspection the bright light seemed to traverse across the sky an incredible distance passing behind or in front of a passing satellite almost as if it was swimming through the sky. It did not follow a straight path. In the image captured you can in fact see several satellites. I have had several other encounters over the years, some closer than others. Some have claimed it to be a firefly. I am sure it wasn’t.