Binoculars

Binoculars are a magnifying device universally used by the United Nations Space Command. They are often equipped with a stand to keep the device steady.

Use
Binoculars are generally used to observe the battlefield, gather information and locate enemies. Marine sniper-spotter teams have spotters with binoculars to observe and locate targets for the sniper. The UNSC binoculars have a digital display, which shows the temperature, as well as the distance to the target.

The Covenant ground forces use magnifying monoculars to observe the battlefield, filling a similar role as the binoculars.

In-game
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's more detailed and that it shows distance to the target. The Sangheili Combat Harness also has a binocular system. Otherwise similar to the MJOLNIR's binoculars, it has a slightly different visor shape.

The UNSC binocular prop appears frequently in Halo 2.