There is no boss on the pewter moon. The pewter moon is where you meet friendly aliens, who allow you to build a better spaceship. There are three bosses in Astro Knights. One on the Jungle Planet, one on the Fire Planet, and one on the Ice Planet. Good luck!
where is the boss on pewter moon poptropica
On the Pewter Moon, see the manager at AstroZone about replacing your ship.
Somehow
Pewter.
Using digletts cave to get to pewter city you need to go east of pewter city and mt moon is over there.
on pewter moon
pewter moon
In Pewter city, behind the gym.
you can just fly back
mt. moon is between pewter city and cerulean city
You can travel to Mt. Moon by following the path east of Pewter City.
Use the UFO. (The saucer Excalibur in the mud swamp past the mill.) To use it you need to find a fuel rod and the coordinates. Once you get to the Pewter Moon you can make a new spaceship. (see related questions)