A sight tube used together with a whole horizon mirror provides the sextant with an incredible field of view and minimizes celestial body movement. The navigator now has the ability to quickly set a stubborn sun on the horizon in rough seas or to capture a sun line from a momentary glimpse through an overcast sky.
An old scope beyond repair can serve as a sight tube if the lenses are removed. There are after-market sight tubes available for most sextants at a reasonable cost as well. Why not include one in your sextant box?
— Greg Rudzinski is a retired merchant mariner enjoying life aboard his Bruce Roberts Offshore 38 ketch Nightcap at Channel Islands Harbor, California.