- For the game, see S.T.A.L.K.E.R.: Clear Sky
We're researchers. We're trying to figure out the nature of the Zone, determine the reasons which caused it to appear, and formulate the rules that govern its existence. We are not consumed by a quest for money, we don't seek fields of artifacts, and we're not interested in turf wars with other factions. That is why we're hiding here in the Swamps and concentrating on our research. Our forte is not combat, but knowledge - knowledge of the Zone, accumulated over years of research. We know more about it than stalkers and the government combined, and our research was finally shaping up into a sound, coherent picture... until the massive emission a few days ago...Lebedev describing Clear Sky
The Clear Sky (Чистое небо) faction is an independent scientific/military organization focusing on understanding the Zone. It only appears in S.T.A.L.K.E.R.: Clear Sky.
One of the first factions established in the Zone, Clear Sky was dedicated to researching the Zone and learning its inner workings, and are not averse to hiring mercenaries to perform missions, much like the Ecologists faction. However, unlike the Ecologists, they are more than willing to resort to violence to get their way, and are as fiercely protective of the Zone as Freedom, or even the Monolith.
The faction is neutral to all other factions of the Zone, with the exception of Renegades, Bandits and the Monolith.
The Clear Sky faction headquarters are located in an isolated village in the Great Swamps. They are poorly-equipped at the beginning of the game, likely due to the fact they didn't have to fight anything other than mutants as the Swamps were mostly inaccessible prior to the Second Emission. This later changed and Clear Sky began to obtain higher tier weaponry for use at the later battle in the Chernobyl NPP.
Clear Sky was formed after a split occured among members of the research team that caused the Zone to emerge in the first place. Disputes concerning cleaning up the aftermath of the failed experiment caused approximately a half of the scientists to leave. Three of them (N.A. Lebedev, V.I. Suslov and E.F. Kalancha) formed Clear Sky in order to research the Zone and find a way to remove the fracture in the noosphere or at least contain it so that it can be lived with.
The faction set up a camp in the isolated Swamps. Unlike most of the Zone factions, only their members know the location of their base: if the player needs to go there, the guide will blindfold Scar, so he cannot memorize the road.
The Clear Sky faction begins the game as a woefully under-equipped faction isolated inside the Great Swamps. Led by Lebedev, this faction aims to study the Zone. These plans are unfortunately ruined with the Second Emission that begins the game. The Emission devastates the Clear Sky ranks, and also ruins most of their data on the Zone as anomalies change and move, and even worse, allows free access to the Great Swamps, allowing unsavory Renegades into the Swamps. The only good news to arise from it is the discovery of Scar, a mercenary who was escorting a team of Ecologists through the Swamps. Although the Ecologists that Scar was escorting were killed by the Emission, Scar himself is alive and well, arguably blessed with extra health and strength from his exposure to the Emission. Unfortunately, Scar's nervous system is also irreparably damaged by the Emission, and he is notified that further exposures will kill him.
With Scar's help, the Clear Sky faction pushes the renegades out of the Swamp, and starts to theorize a solution to the rash of emissions scarring the Zone. Eventually, Lebedev and Beanpolev conclude that a group of stalkers penetrated the center of the Zone, and the emissions are the zone's reaction, attempting to kill anyone who had been there. Lebedev directs Scar through the Zone, attempting to gather evidence on this group, where they learn of two Stalkers in particular, Fang and Strelok, members of the 'Strelok Faction'. Lebedev mobilizes Clear Sky, and leads the first major foray into the Zone since the First Emission, using the help of mercenaries to push into Limansk, and then all the way up to the Chernobyl NPP.
With the help of Scar and Leshiy's mercs, the Clear Sky faction secures the bridge to the abandoned city of Limansk. After fighting through waves of Bandits and Monolith fighters, the faction, still with Scar, reaches the derelict Limansk Hospital, a direct way to the center of the zone.
Once there, the faction is engaged by the Monolith experts protecting the area. Using the faction's prototype EM1 Rifle, Scar disables Strelok's psi-protection, hoping it would make the Zone more stable.
In the aftermath of this "victory", the Common Consciousness, who noticed the invaders, releases a powerful blowout. This resulted in Scar, Lebedev, and all the Clear Sky members either dying or becoming brainwashed in the Monolith faction, or as agents of the C-Consciousness, much like Strelok.
After Clear Sky
Without Lebedev and most of their manpower, it's likely the faction remnants disintegrated and became a mere footnote in Zone history. All that is left of their technological prowess is a single CHN-3a Battle Armour that can be acquired for a hefty sum.
The prototype EM1 Rifle later ended in the hands of the Monolith faction which produced in small amounts a new and deadly version of it, named the Gauss gun. Also, the rare FT-200M which was used by Clear Sky was later issued to a few Monolith experts.
By the events of S.T.A.L.K.E.R.: Call of Pripyat, the only confirmed survivors of the faction were Nimble and Novikov. Nimble started working for Sidorovich in the Cordon before becoming a weapons trader aboard the Skadovsk, while Novikov was contracted by the Ecologists and started working with Hermann and Ozersky in Yanov.
Something worth noting is that according to Barkeep, Strelok's friend Ghost assassinated the leader of a faction known as "Final Day". According to early builds, they were very similar to the Clear Sky faction, as they were studying the Zone. This could imply Final Day was a successor of Clear Sky.
Clear Sky is initially one of the more poorly equipped factions, but once mobilized boasts an arsenal probably second only to the Monolith, sporting heavily upgraded assault rifles complete with scopes and grenade launchers.
- CS-3a Body Armor — The Clear Sky faction's basic armor using light kevlar armor with low anomaly protection. However its armor stats are slightly better than Leather Jacket and Bandit jacket.
- CS-2 Body Armor — Clear Sky's medium armor. It serves as a middle ground between the CS-3 and the CS-1. It is roughly around the same effectivenness as a PS5-M Universal Protection.
- CS-1 Body Armor — An armor combining military grade Kevlar armor and above average anomaly protection. Comparable to the Guardian of Freedom Suit, albeit slightly superior at the cost of one less artifact slot.
- CS-3a body armor (Call of Pripyat) — Clear Sky's flagship suit. Never widely used due to cost. It is a modified CS-1 suit. Offers the best anomaly/radiation protection and ballistic protection out of any other Clear Sky suit. Featured only in S.T.A.L.K.E.R.: Call of Pripyat where it is sold by Nimble. Protection is in between the Skat-9 military armoured suit and the SEVA Suit.
- Leather jacket
- Sunrise suit
Clear Sky was conceived back during the development of Shadow of Chernobyl and is mentioned in text files for the PDA's encyclopedia, described as "Peculiar stalkers environmentalists. Study area, looking for a method to cure the world of this plague. All groups are neutral.".
- Clear Sky's uniform is similar to that of the pre-released Ecologists from S.T.A.L.K.E.R. Oblivion Lost; infact, Clear Sky may have been a way to bring back the early Ecologists, as they looked more like stalkers with blue uniforms.
- The sky-blue camouflage worn by Clear Sky is similar to the blue digital camouflage used by some Asian and Middle-East armies, as well as US Navy sailors.
- After the faction's downfall, the only known survivors are Nimble and Novikov (a.k.a Grey).
- The Clear Sky base and the Great Swamp appear in Shadow of Chernobyl's PDA Map, but are both inaccessible.
- In the Russian and Ukrainian editions of the game, the name and descriptions for this armor belong to the CS-1. It seems that there was an oversight during translation and GSC switched the armors around. In canon, CS-1 is the weakest armor, CS-3 is the higher one.