@Etryus
Yeah, that Meteor shooting gallery trophy/cheeve was a nightmare to get. Here's what you do:
Turn up the game's brightness all the way. If necessary, turn up the brightness settings on your television as well. You'll be able to see the meteors coming long beforehand. The most important thing about this? STAY CALM. The biggest blunder you can do is get panicked and start shooting wildly at everything that comes at you. Focus on the meteors coming directly at you, the ones that are far off to the side don't do as much damage as direct hits. Take your time, aim the cannon, and use only ONE barrel. If you use both you'll overheat the gun quickly. Remember to focus first on the bigger ones, since they split into smaller chunks once you blow them up. One hit from a large meteor can easily do 40% damage to the hull.
The meteor shooting gallery isn't affected by difficulty, so don't bother setting it to easy. You'll get a bit better each time you attempt it. After not being able to nail that cheeve for over a year, I read the "stay calm" strategy and nailed it in under an hour.