The astro-viewer is a Precursor artifact in Jak 3. It is an ancient structure located in Southern Haven Forest, and is activated by five smaller artifacts, including the holo cube, the beam generator, the Prism, the quantum reflector, and the time map. The astro-viewer appears to function as a very powerful telescope, allowing Jak to see far into space. For unknown reasons, when the time map is added, Jak is able to link into the Dark Maker ship systems and control some of the machines.
After the termination of dark plants in Southern Haven Forest during the "Kill dark plants in forest" mission, six platforms appear in the water at the center of the forest. Once Jak collects four of the five artifacts, he is able to defeat five ring challenges (in the "Beat pillar ring challenges" mission) set by statues similar to oracle totems in order to raise the platforms and approach the astro-viewer itself. He is then able to use to astro-viewer and see the Dark Maker ship. When Seem gives Jak the time map, Jak is able to link into the Dark Maker ship and manipulate some of the machines during the "Destroy dark ship shield" mission. He first had to fight his way through several troopers and hornets who had intended to take control of the Forest together with the astro-viewer.