Pray to your lucky stars that this weapon hits. A star shaped flare is shot. Upon resting, a huge star flies downwards into the screen and crashes into the ground, dealing a good amount of damage. However, shooting star can land in a large variety of places. The flare that you shoot only marks the general area of where the star lands. In fact, it is somewhat rare for the star to land where the flare rests, so a miss with the flare is not really a bad thing.
Similar to weapons like Synclets and Needler, StarFire's spread is caused by each shot having a varied power. This weapon is best used at low angles and high power to minimize the spread.