What is a disadvantage of the Galilean telescope?

The Galilean telescope, known for its simplicity and ease of construction, has a smaller field of view compared to other types of telescopes, such as the refractor or reflector designs. This is mainly due to the optical arrangement it employs, typically utilizing a converging lens as the objective and a diverging lens as the eyepiece. As a result of this configuration, the viewing angle is constrained, limiting the field of view.

In practical terms, a smaller field of view means that when observing celestial bodies or terrestrial objects, the observer will have to move the telescope more frequently to keep the target in sight, as less area is visible at any one time. This can be particularly challenging in astronomical observations where objects may roam across the sky or when tracking moving subjects.

Other options refer to different characteristics: using mirrors is related to other types of telescopes like reflectors, larger fields of view pertain to designs such as wide-field refractors, and the inversion of images commonly occurs in other telescope designs, but in the case of the Galilean telescope, while it does produce an upright image, its primary drawback is indeed the limited field of view.