What is a disadvantage of the Keplerian telescope?

The disadvantage of the Keplerian telescope being that the image is inverted is accurate because this optical design produces an image flipped both horizontally and vertically. In many observational contexts, especially for terrestrial viewing, an inverted image can make orientation and navigation difficult, as objects appear opposite their actual position. This inversion is inherent to the way lenses work in this type of telescope, which uses an objective lens and an eyepiece.

In contrast, some other telescope designs employ additional optics to correct for this inversion, particularly when a right-side-up image is desired. This characteristic of the Keplerian design is a well-known consideration in its operational use, particularly affecting those who use it for applications beyond astronomy, such as birdwatching or general terrestrial observations. The other choices do not apply since they describe either benefits or features that are not inherent disadvantages of this telescope type.