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General Purpose Guide

NZ View-131Commet 150mm-469 


By general purpose we refer to a telescope that can be used for land/sea viewing and astronomy. 

Click here for complete list of all our General Purpose Telescopes.


Following is a summary of the key points you should consider when purchasing a general purpose telescope
 
1. Aperture
  • A telescopes aperture is the diameter of the main lens or mirror ( slightly less than the outer diameter of the main tube).
  • Its purpose is to collect light and is the most important technical consideration.
  • The greater the aperture, the more light collected and this combined with the eye piece used determines the magnification and clarity of the object you are viewing.
  • Light gathering power is proportional to the area of the lens or mirror, which depends on the square of the radius, so it increases rapidly with increased aperture. For example, a 200 mm telescope does not gather twice as much light as a 100 mm telescope -- it gathers about four times as much.

    Aperture is very important for visual observation (i.e. using your eye and an eyepiece) because it determines what you can see.

Aperture-766
 
2.  Magnification
  • A telescopes magnification is important but not as important as aperture.
  • A telescopes magnification can be changed by the eye piece used.
  • Maximum useful magnification is approx. 2 times the aperture in mm, for example a 102 mm aperture telescope can usefully magnify up to 204 times. Trying to use an eye piece to magnify more than this will result in a narrow field of view and unclear image.
  • Less magnification is often preferred as you get a wider field of view and increased clarity.
Magnification trees-260
Increasing magnification / decreasing field of view
 
3. Size and Portability
  • Some telescope designs can be large and heavy meaning they take up a lot of room when left set-up and are difficult to move around your house or in your car.
 
4. Mounting System
  • The mounting system refers to the way the telescope tracks moving objects.
  • Typically an alt-azimuth or AZ mount is the best choice for a general purpose telescope as moves the telescope in a simple left-right and up-down motion.

5.  Ease of operation
  • The easier it is to operate, and the more your telescope the more you will use it and enjoy it. We recommend refractor type telescopes on an AZ mount as being both simple and intuitive to use.

Saxon 1206 AZ3 Refractor Telescope
Refractor Telescope on an AZ Mount
 6.  Price
  • Usually has a close relationship to aperture, the bigger the aperture, try to set a budget you are comfortable with.
 
So if you want a general purpose telescope 

For a complete list of all our General Purpose Telescopes

If you would like to email a query or talk to someone then Contact Us