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After completing Fame or Shame (the mission in which Trevor and Michael reunite), a Strangers and Freaks mission for Franklin will appear in Sandy Shores - we've marked at as a green question mark on the map. Travel there to meet Omega, a classic alien theorist.
Omega asks you to recover 50 space ship parts scattered across the map. This is where things get tricky - finding all 50 parts is difficult. Fortunately, we've done all the searching for you. Follow along to learn the locations of every space ship part.
Head southwest from Omega to find this array of satellite dishes in the desert. A space ship part lies on the walkway of the westernmost dish.
A bit further west you'll find a small cluster of trailers. Next to the large boat is another space ship part.
Head north from where you met Omega to find an alien-themed park in the middle of the desert. At the top of this hill lies another space ship part.
Southwest of Part #3 is a series of large white rocks in the Sandy Shores desert. Along the edge of the largest one lies another space ship part.
Now head north to the Alamo Sea. This part is in the water, so you'll have to dive. Follow with our map and the in-game map from the screenshot closely to find the exact spot. Listen for the hum of the ship part for more help.
Head to the lovely San Chianski Mountain Range to the game's northeast. Here you'll find a quiet little area called Catfish View. Immediately inside this shed is another space ship part.
This one can be found in Grapeseed. In the south-central part of the town is a large farm. Head there to find a space ship part in the middle of a cow pen.
Using the map, follow the road the hooks to the left to the east of Mount Chiliad. Just before the road ends, you'll spot this shed. The space ship part is inside.
Just outside of Paleto Bay proper is the Donkey Punch Family Farm. In the center you'll find a large barn, and inside of that you'll find another space ship part.
The location marked on the map is Paleto Bay fire station. In the back of the complex is a simulated burned-out building. Ascend the fire escape to its top floor to find another space ship part.