This guide is suitable for current RuneScape and Old School.
Talk to the Observatory Professor who is in the house north of the Observatory, near Castle Wars.
You will learn that a village of Goblins have sabotaged his telescope, and he asks for your assistance in fixing it. He will tell you that he requires 3 planks to fix the tripod, molten glass to make the lens, and a bronze bar for the tube.
If you are having trouble finding those items, talk to the assistant and he will help you find them. The best option would be to buy them through the Grand Exchange. Give the items to the Professor once you have them.
The Professor will realise however, that the Goblins have stolen his lens mould, and will ask for your help in getting it back. He will give you the molten glass and will tell you to ask the assistant for more information on where the lens mould could be found.
Talk to the assistant and he will tell you that you should try the dungeon in the village full of Goblins nearby.
Head south and then east to arrive in the little village full of Goblins. Locate the house with stairs and climb down.
Note: Various chests are infested with Poisonous spiders so do not open any other than what the guide states.
Head south east through the tunnel of Goblins and open the chest to find a Goblin Kitchen Key. If it is not in this chest, check the chest behind it.
Now head to the far north of the tunnel and follow it around until you find a Sleeping Guard.
Prod him to awaken him, and he will turn into a level 42 Goblin. Either attack him or run past him, and enter into the kitchen using the key. Inspect the stove to find the lens mould, and return this to the Professor.
Making the Lens
The Professor will then remember that he cannot remember how to make the lens, and will ask you to make it for him. Use the molten glass on the lens mould to create the lens. Give this back to the Professor and he will tell you to meet him at the Observatory, but the bridge is broken so you will have to travel through the Goblin dungeon.
Head back to the Goblin dungeon and follow the tunnels around until you come to another ladder. Climb up it to arrive in the Observatory. The Professor will fix the telescope, and will then ask you to look through and tell him what you saw. Look through the telescope, and then climb down the ladder and observe one of the star charts to identify the constellation.
Congratulations! Quest Complete!
Guide Made by: DaDa
Corrections submitted by: Doctor Shemp, DaDa, Ashwin, Power of Five, Umbra