From Halopedia, the Halo wiki
Binoculars are a device which allows the user to view distant objects by magnifying them via a system of lenses and prisms. A spotting scope is a specific variation of the device commonly employed by the UNSC.
Binoculars are generally used by United Nations Space Command military forces to observe the battlefield, gather information and locate enemies. Marine sniper-spotter teams have spotters with spotting scopes to observe and locate targets for the sniper. Certain sets of UNSC binoculars have a digital display, which shows the temperature, as well as the distance to the target. The UNSC spotting scope is equipped with a stand to keep the device steady.
MJOLNIR Mk VI featured in Halo 2 was the first armor to have magnification system in-game. The MJOLNIR armor's binocular system featured in Halo 3 has the same radius as the one in Halo 2. The only difference is that it is more detailed and that it shows distance to the target. The Sangheili combat harness also has a built-in magnification system. Otherwise similar to the MJOLNIR's binoculars, it has a slightly different visor shape. Subsequently, the ODST armor from Halo 3: ODST, MJOLNIR Mark V from Halo: Reach and MJOLNIR GEN2 from Halo 4 all feature a built-in magnification system.
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