By definition, black holes give off no light. This makes the idea of trying to see one sound a bit challenging. Fortunately, black holes don’t always live in isolation, and one of the most famous — Cygnus X-1 — has a partner that shows up through any backyard instrument.

Cygnus X-1’s stellar companion is a blue supergiant cataloged as SAO 69181. This star shines at magnitude 8.9 in the central regions of the constellation Cygnus the Swan, which passes nearly overhead on September evenings for observers at mid-northern latitudes.

Use the circular StarDome map at the center of this issue to locate Cygnus. Next, home in on Eta (η) Cygni, a 4th-magnitude star that lies 13° southwest of the Swan’s luminary, 1st-magnitude Deneb. Scan 0.4° east-northeast of Eta to find SAO 69181. It’s the middle object in a line of three equally bright stars. When you spot it, you won’t be seeing light from the black hole, but it will be literally from the next closest thing. — R. T.