Which Telescopes?


Which telescope?
People often ask me “which telescope” to buy, so I am going to help you here,
please click the blue text below for your reference information to print out.

Telescope Basics
These days there are three main types of telescopes :-

  • Refractors ~  Use lenses to collect and focus light.
  • Reflectors ~  Collect light with a mirror.
  • Cassegrains ~  Use a combination of mirrors and lenses.

To choose the right telescope?
Telescopes are judged not by their magnification but by their aperture.

Focal Length and Focal Ratio?
Telescopes, like cameras, have `f` numbers :-

  • Focal Length  –  The distance between a lens or primary mirror and the point where the light rays  it collect are brought into focus.
  • Focal Ratio  –  The ratio of the focal length of a lens or primary mirror to its diameter.  (A focal ratio of, say 8 is written as f/8.)

More information :-  Focal Length and Focal Ratio?

The magnification of a telescope depends on the eyepiece used.
Telescopes usually come with a selection of eyepieces that offer low, medium and high powers.

Eyepiece Calculator

  • The eyepiece calculator reveals the observing potential of your telescope with eyepieces, it accepts basic information about your telescope and displays results for all eyepieces.
  • Refer to the diagram and tables below for the definition of the input and output parameters.

Telescope Types
More Information about telescope types :-  Advantages and Disadvantages


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