Triangle Shaped Dark Craft w/ 3 lights in the corners.I was looking up at the stars whilst sitting on my deck and thinking about light pollution. I had to block the street lights from view and their orange glow to see the stars but they were still very clear for Chicago, and then as I was staring at the constellation Orion and Sirius, three red lights in a triangle shape with a dark barely visible frame or body above them began passing through what looked like fairly low altitude and mostly opaque clouds right in the left and center of my field of view.They seemed to appear out of nowhere and the craft appeared to be very large (about 1.5" from my perspective and I'd estimate that it was at an altitude of 10,000 ft and approximately 10 miles away from me).It moved forward slowly bearing east to west and then only slightly but immediately it elevated and then went back down in altitude, it shifted speeds and altitudes as it passed into the orange glow reflecting up from the city. I tried to take out my phone camera but it was too late and I was too affixed during the incident to break my focus.