When you have recovered a fuel rod for the saucer, the instrument will let you use the X and Y dials to set the coordinates. But the planet coordinates the Queen gave you are too far away. You will need to use the coordinates from Mordred's missing journal page, which are X-56 Y-52.
(see related question)
The Queen will give you a card with three sets of coordinates, the planets that the three knights have gone to. However, you will need a closer set of coordinates, and there is one on the missing page from Mordred's Journal. (It is under his bed in the Museum, and the numbers are X-56 Y-52.)
The key to the underground door (between the hay bales) is in a secret room under the fountain in the village square. You will need the Cosmic Symbols password card.
Go to the Maid's Room in the castle (first floor left). Take the secret message from there to the second floor inside the Mill. The goth girl will give you the Cosmic Symbols password card. Go to the plaque on the fountain. Press the three symbols, and the center Sun, and the plaque will open. Enter the secret chamber and talk to the kid on the far right, who will give you the key.
The Golden Key - see related question
You don't have enough fuel to reach the planets whose coordnates the Queen gave you. Instead, set the coordinates for the Pewter Moon (X-56 Y-52) as shown on Mordred's missing journal page.
The coordinates are locations (destinations) that are entered on the dials in the saucer Excalibur. When you have a new spaceship, the coordinates are displayed in the screen to tell you where you are. (see related question)
You have to get a new fuel rod for the saucer and some coordinates to fly to. (see the related questions)
On the saucer Excalibur, you must enter coordinates before the ship will launch. (see related question)
The saucer Excalibur is crashed in the mud swamp to the right of the Mill.
There is nowhere to enter a password. Fix the saucer and get the coordinates you need to fly it. (see related questions)
You have to fix the saucer by obtaining a new fuel rod. There is one in the robot invader held in the dungeon. Once it is replaced, you can dial in the coordinates to launch the saucer. (see related questions)
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You have to fix the saucer by obtaining a new fuel rod. There is one in the robot invader held in the dungeon. Once it is replaced, you can dial in the coordinates to launch the saucer. (see related questions)
You need a new green fuel rod and space coordinates to use the saucer Excalibur. (see the two related questions)
The Queen gives you the coordinates for the planets where the three space knights have gone, but for the saucer Excalibur they are too far away. The nearby moon at X-56 Y-52 is noted on the page from Mordred's journal (under his bed).
Use the hovercraft in the mill's attic to reach the crashed saucer Excalibur in the mud swamp. Fix the saucer and use Mordred's coordinates to fly to the Pewter Moon. (see related questions)
Once you have a new fuel rod, dial in the coordinates X-56 Y-52 to launch the saucer. (see related questions)