He was then able to calculate the apparent height of a distant object using two similar triangles.

The subject fixates a distant object with both eyes open and appropriate correction in place.

Each vane (also called a pinnule or pinule) has a hole, slot or other indicator through which one can view a distant object.

To focus on a distant object, a horse will raise its head.

This kind of mirage can involve almost any kind of distant object, including boats, islands, and the coastline.