Your health meter is now at it greatest amount. You will begin flying through space. The first enemies to attack you are little ships which fly up and down in square-wave patterns. Platforms take the shape of satellites here, and the second one will have an S capsule sitting on it. A face will start to form shortly after. Take it out quickly so that it doesn't harass you further into the stage.
You will approach land along the bottom, along with the first P capsule. On the ground, you will find structures that have a yellow dome on top of the center. This dome can fire three bullets that spread out. Remove the dome to reduce the threat. Little creatures will arrive on flying saucers to confront you.
When a second head starts to appear, you'll see another domed structure. Remove the dome before focusing on the head, then do your best to destroy the head as quickly as possible. A second P capsule will appear on a satellite. As an upgrade, you'll receive a smaller turtle below the one you're flying in which will also shoot forward.
A third head will appear around the same time as another dome. Remove the dome, then the head. Some new enemies will appear before the screen starts to darken and the scrolling speeds up. You will start dashing through a series of small columns. For the most part, you are safe to stay near the bottom of the screen, weaving up and down between the two lowest sets of columns. The enemies should remain above you and not present much of a threat.
The boss of this stage resembles a cyclops head on top of a large flying saucer. It flies in from the right, and starts floating up and down as it slowly approaches the left side of the screen. Eventually it gets far enough and starts slowly returning to the right while it continues to hover up and down. It fires a set of bullets, some of which go forward, while others are angled down. There are two large rocket-arms on the side of the saucer. When the boss take damage, it fires one of these arms in Apollo's direction (it is immediately replaced by another arm).
You are safer near the top of the screen then the bottom. If you powered up your weapon and have the second turtle, you can let the shots from the lower turtle do most of the work, along with your bombs. When the saucer flies up near the top, you can concentrate your fire on the head. Move out of the way when the arms fly towards you. Even though you have a lot of health, the weapons can do a lot of damage, so avoid getting hit at all costs.