original: The first fifteen asteroids to be discovered were given symbols by astronomers as a type of short-hand notation.
simplifications: Astronomers gave the first 15 discovered asteroids symbols as abbreviated names. The fifteen first asteroids found by astronomers were named with symbols. The first fifteen asteroids discovered were given symbols by astronomers. This was used as a short-hand notation. The first fifteen asteroids discovered got symbols by astronomers. It was a type of short-hand notation. The first fifteen asteroids discovered were given symbols by astronomers. The first fifteen asteroids discovered were given symbols as a type of short-hand notation. The first fifteen asteroids discovered by astronomers used short-hand notation to give them symbols. The first 15 asteroids found were given symbols by astronomers as a quick code. The first fifteen  minor planets to be discovered were given symbols by astronomers. These symbols were used as a type of short-hand notation. The first fifteen asteroids to be found have been given symbols by astronomers as a type of short-hand notation.