Long-focus lens

[1][2] It is used to make distant objects appear magnified with magnification increasing as longer focal length lenses are used.

This effect is similar to moving closer to the object, but is not the same, since perspective is a function solely of viewing location.

Long lenses are often used with a tripod, because of the increased weight and the fact that the effect of camera shake is magnified.

The 1.25 inch mount is smaller than many film and sensor formats so they tend to show vignetting around the field edges.

[8] Telescopes are normally intended for visual use, so they are not corrected to produce a large flat field like dedicated camera lenses and tend to show optical aberration.