These plans are for a homemade spotting telescopes.
The prismatatic telescope, is an astronomical telescope plus a pair of prisms for erecting the image. The most common example of this type of construction is the binocular instrument. One half of a binocular is a monocular.
Some telescopes are used for a specific purpose and are named accordingly; a typical example being a spotting scope, which is used to view the target in rifle shooting.
Prisms: Prisms are polished, angular pieces of glass, the kind commonly used in telescopes being 45-45-90- deg. prisms. The long side is the face, while the two short sides are the reflecting surfaces. The size of the prism is the width of the face. Fig. 44 shows how the prisms are used in a telescope.
Made specifically for telescopes, the prisms are grooved across the face in order to make a definite dividing line and avoid ghost images which would be caused by overlapping rays at this point. The ends are usually rounded to conserve space....