Observatory Quest

The Observatory Quest is a standalone quest where you must help the professor of the observatory repair the building and restore it to its former glory.

Ruination
Travel to the observatory north of Castle Wars and talk to the professor in the reception. Bring up the observatory and you'll be informed that the observatory telescope is broken. He explains that the houses up on the hill outside, have been occupied by unruly goblins, who have caused him nothing but stress.

The professor asks for your help, the idea presented by his assistant, in rebuilding the telescope. When you agree, he'll ask you to get some materials for the telescope parts.

First, he asks you to provide him with 3 wooden planks for the telescope base. Talk to the assistant, then the professor to turn it in. Next, give him a bronze bar for the tube and some molten glass for the lens. To make the lens into an exact shape and size, you'll need a lens mould which, unfortunately, the goblins have stolen.

A Goblin Horde
Leave the house and head east to one of the abandoned buildings. If you didn't bring an antipoison, there is a super antipoison (1) respawn in the south-eastern building.

Climb down the stairs in the west building to arrive in a maze-like dungeon, which is littered with chests throughout it. One of these chests contains the goblin kitchen key - its location is random for each player - while the others hold a single dose of anti-poison, a level 15 poison spider, or simply nothing.

Run to every dead end and search the chests until you find the kitchen key. Once you do, head to the sleeping guard guarding the kitchen to the north. Prod him awake, and he'll turn into a level 28 goblin guard. You can either kill him or lure him far enough from the gate to get into the kitchen. Inspect the goblin stove there to find the lens mould, which the goblins were apparently using for cooking.

Stellar
Head back to the professor with the mould and he'll instruct you on making a telescope lens; simply use the molten glass on the lens mould. Talk to the professor again and he will ask you to meet him at the other side of the observatory.

Head back to the dungeon and follow the path around and up the stairs to the south. Speak to the professor and watch the long cut-scene of him fixing the telescope. Finally, go up the stairs and talk to the professor again, who tells you to have a look through the telescope and note the constellation that you see.

Rewards

 * 2 Quest Points
 * 2,250 experience
 * 875 experience in, , , or (random)
 * Depending on the astrological sign you see through the telescope, you will receive one of these items:
 * Uncut sapphire (Aries, Capricorn, Leo, Libra, Virgo)
 * About 25 Water runes and an Uncut sapphire (Aquarius)
 * Amulet of defence (Cancer)
 * Black two-handed sword (Gemini)
 * 3 Law runes and an Uncut sapphire (Libra)
 * 3 Fish pies or 3 Tunas (Pisces)
 * Maple shieldbow (Sagittarius)
 * Weapon poison and an Uncut sapphire (Scorpio)
 * Super strength potion (1) and an Uncut sapphire (Taurus)
 * You can talk to Historian Minas at the Varrock Museum to receive 5 Kudos.
 * You can talk to Historian Minas at the Varrock Museum to receive 5 Kudos.

Music unlocked

 * Serenade - At the observatory
 * Expedition - Can also be unlocked during Troll Stronghold quest.

Spirit of Scorpius
Should a player look through the telescope again after the quest is completed, they will see the Scorpio constellation. The Observatory professor will suggest going to see his assistant. Upon speaking to the assistant, who reveals that his name is Patrick, he'll thank you for having made his life easier and give you a jug of wine.

He also mentions a book on the nearby table named 'The book of astronomy', which speaks of Scorpius' grave. Travel past the abandoned buildings, and keep going north until you see some level 40 ghosts near the entrance of the Ourania runecrafting altar. The spirit of Scorpius is located in this area with the ghosts; after a brief conversation, it will give you an unholy mould and tell you to return when you are worthy. With the mould, a ball of wool and a silver bar, make an unholy symbol and return to the grave so that Scorpius can bless it.

Trivia
Observatory Quest
 * The entrance to the dungeon used to be at the observatory. It has since been moved in an update and is now located on the hill.