The Dusk Ball is a PokéBall that is more effective within Dark enviornments. Within Caves or at night-time, the Capture Rate is a massive 3.5. However, at any other times, the Capture Rate is 1 ~ Serebii
According to Serebii, the Dusk Ball works "within Dark environments", and space is pretty darn dark. Unless Game Freak had another lapse in logic, outer space is counted as a dark environment. (You could also say that space is considered nighttime).