Soligor 8/500mm MC C/D | spiegel Telelens

This is a Soligor 500mm f/8 MC C/D mirror telephoto lens, a compact telephoto lens that uses mirrors instead of a series of glass elements to achieve the focal length.

Main Features
Compact design: Due to the mirror-based (Maksutov-Cassegrain) design, the lens is significantly shorter and lighter than traditional lenses with the same focal length.
Large diaphragm

This type of lens has a fixed aperture, usually f/8, which means that the amount of light entering cannot be manually adjusted (except with filters).
T-mount: Originally designed with a universal T-mount (T2-mount), allowing it to be used with adapters on various camera systems such as Canon, Nikon, or Pentax.
Macro mode
The lens often has a relatively short minimum focusing distance, which is marketed as a 'macro' mode, although it is more accurately a close-focus capability (approximately 1:4 reproduction ratio).
Unique Bokeh: Due to the central mirror in the optical path, the lens produces a characteristic donut-shaped (ring-shaped) blurry area (bokeh) in the background.
Low chromatic aberration: An advantage of mirror optics is that there is generally very little or no chromatic aberration (color shifting).
The lens is very suitable for photography in bright daylight, such as nature or sports photography, due to its fixed f/8 aperture.