Glossary | Telescopes | Optics
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 (14)
Describes the exact structure of the telescope thereby further subdividing the different types of telescope.