🔍 Key Concepts

• Adjustable sextant errors vs. nonadjustable (permanent) errors • How side error and index error are normally corrected by the navigator • Which parts of the sextant the navigator can physically adjust during a pre‑sight check

💭 Think About

• First separate in your mind: which errors can you fix yourself with the sextant’s adjustment screws, and which require a repair shop or manufacturer attention? • Think about which components (mirrors, telescope, frame/arc) you routinely touch and line up during the ‘sextant on the dock’ checks before taking sights. • For each choice, ask: is this something I would normally clear by sighting a star, horizon, or checking on a vertical object, or is it ‘built into’ the metalwork and not user-adjustable?

✅ Before You Answer

• Identify which listed errors are normally corrected by adjusting the index mirror, horizon mirror, or telescope. • Recall which error is due to the arc or frame not being perfectly shaped or centered, and whether a user can practically fix that at sea. • Before picking, cross out any error you remember routinely clearing during a standard sextant adjustment procedure (index, side, and collimation checks).