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Home > Glossary > Telescopes > Optics

Glossary | Telescopes | Optics

A telescope tube is referred to as an optic because it contains the components necessary to collect and concentrate light.

More information:

  • Aperture
    The aperture indicates the diameter of the objective lens or the mirror.
  • Aperture ratio
    Is the ratio of the aperture to the focal length of a telescope.
  • Bandwidth
    Specifies the width of the area through which light of certain wavelengths is allowed to pass. Light is blocked outside of this range.
  • Blocking Filter
    The deflection optics with the eyepiece receiver also accommodate the blocking filter.
  • Coating (3)
  • Corrected Field
    The optics’ field is illuminated without errors.
  • Double Stack
    Many solar telescopes are also available with a Double Stack.
  • Focal length
    This is the distance between the objective lens or mirror and the focal point.
  • Lens design (2)
  • Light gathering capacity
    Light-gathering capacity of the telescope compared to the eye.
  • Limit value
    Describes the brightness of a star or point-shaped object, which can still just be distinguished by the telescope. The naked eye, for example, can make out stars with a magnitude of up to 6.
  • Max. useful magnification
    The telescope’s magnification should not exceed this factor, because otherwise the image will appear weak and dark.
  • Resolving capacity
    The ability of the optic to discern the fine detail of objects that are close together.
  • Tube construction (1)
  • Tube length
    Including eyepiece, but excluding dew cap.
  • Tube material (1)
    Most telescopes are made of steel, aluminium or carbon fibre.
  • Tube weight
    The weight of the tube is critical for the correct choice of mount.
  • Type
    There are basically two different types of telescope. A distinction is made between refractor (lens) and reflector (mirror) telescopes.
  • Type of build (13)
    Describes the exact structure of the telescope thereby further subdividing the different types of telescope.
  • 27.09.2022

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