Prince of Persia: The Forgotten Sands Walkthrough 13 - The Observatory

Go right; use the fissure in the wall and water sprouts to get near the lever.
Bounce off the door and jump onto the lever. Afterwards get onto the platform with the crane and turn it clockwise twice.
Return to the lever, jump onto the fragment of the mechanism and from it onto the waterspout. Use the water to get to the other part of the room.
Run along the wall to the stones and go up. Run towards the second lever.
Jump off the door and two new cranks will show up. Get to the further one and turn it anticlockwise twice.
Now return to the spot at which you came to this level climbing the rocks and turn the crank anticlockwise once. This way you should set the two platforms and be able to jump onto them.
Jump onto the astrolabe and get to the crank in the middle. Turn it anticlockwise twice and jump on the platforms in the direction of the lever.
Move along the wall and you will get to the upper level. Once there, jump onto the lever and two more cranes will show up.
Turn the left one anticlockwise once. Afterwards turn the right one clockwise twice and the left one anticlockwise once.
The astrolabe will begin to turn. Once its fragment gets near the terrace, freeze time, jump onto the yellow platform, afterwards onto the waterspout behind it and on the second platform. Let the time flow and once the mechanism turns round once, jump onto the ...
...half-opened platform. During the next turn, once the rings of the next platform match up, freeze time and jump onto it.
After the next turn, jump onto the next platform and then once again on the thicker part. The astrolabe will start moving again, so once the platform gets more or less opposite to the terrace with a barrier, freeze time and jump onto it.
After getting out of the room, jump towards the fissure in the wall and ride down the flag. Afterwards do a wallrun and you will reach another chamber.
Time to fight Ratash. Wait for the water spouts to appear, jump to the flag and ride it down. You need to have a good reflex, as the water doesn't fall down constantly and you need to freeze time only during the jump to the next spout. Eventually you will get attacked by a big group of sand monsters. Note that the big ones are equipped with steel gauntlets, so you need to trick them before dealing any damage. Let them hit the wall and then hit the from behind with the Power Attack. Once you get rid of everyone, you will be able to enter the trap-filled corridor.