The desirable optical characteristics of good surveying telescope are as follows: (i) Aplanation. Aplanation is the absence of spherical aberration. A compound lens, free from spherical aberration, is known as an aplanatic combination. (ii) Achromatism. Achromation is the absence of chromatic aberration. A compound lens, free from chromatic aberration, is known as an achromatic combination. Hence, Achromatism is desirable in a good surveyor’s telescope.