The damaged saucer Excalibur (in the mud swamp) will not make it very far. You will travel to the nearby moon and get another ship. The three planets to which other knights have traveled is on the Queen's coordinate list. (see related questions)
yes, yes you can
You talk to the knights on different planets
You do not get or use a bucket on Astro Knights Island.
There is no treasure chest on Astro Knights Island.
The planetarium is in the village. The planets in the telescope are not important except as background to the story.
There are no bird eggs in astro knights island.
its on the island
How do you talk to the girl in the hay loft at astro knights island?
Alien spaceships are coming and going from the planets in the solar system. They may attack you when you try to go there.
(See the related questions for each of the three planets, and for the final battle on Mordred's asteroid.)
after u go to all three planets u will find binary bard at the end
On every island you have to be the one to save whatever needs saving. That includes the kingdom in Astro Knights Island.