This is what can go wrong with slide copying. I was experimenting using bellows, a reversed 50mm lens and a light box to illuminate a slide of Cygnus and the North American Nebula. Due to the low light levels from the light box, the lens iris was fairly wide at f4. This resulted in these aberations, which look like mushrooms. It gives a nice 3D effect. When using a flashgun to illuminate the slide and a slower f/no the image was much improved.