All telescopes have two defining characteristics that allow the user to determine how well it will perform at viewing certain objects.

• Focal Length - The distance that it takes light entering the telescope to be focused to a point.
  • Longer focal length telescopes (>1500mm) are more suited to viewing objects at higher magnification. These include planets and the moon.
  • Middle range focal length telescopes (900-1500mm) can be best suited to moderate magnification and wider fields of view.
  • Short focal length telescopes (<900mm) are best used for wide field views of the sky.

Different attachments such as Barlow Lenses and Focal Reducers allow the observer to change the focal length of their telescope, thereby changing its magnifcation and field of view.

• Aperture - The clear diameter of the main lens or mirror. Determining how much light enters the telescopes and gets focused towards your eye.
  • Large aperture telescopes (>250mm) are excellent tools for viewing faint objects such as galaxies and for picking out faint or small detail on the planets
  • Telescopes between 150 and 250mm are useful for viewing a wide variety of objects and still remain portable.
  • Those that have apertures below about 150mm are excellent for viewing the planets and bright deep sky objects.

Mentioned above are two other terms 'magnification' and 'field of view'.

• Magnification is a product of the focal length of the telescope and the focal length of the eyepiece used. A 1500mm focal length telescope with a 10mm eyepiece gives 150x magnification (1500/10). The highest magnification that any telescope can give is about 2 - 2.5x it's aperture in mm. So a 114mm telescope's is about 230x maximium magnification.
  It is important to note that magnification is the least important characteristic to look for when selecting a telescope. Small telescopes advertised as magnification only or "450x!" should be avoided.

• Field of view is the amount of sky (in degrees) that your telescope can see at once. It is a product of the magnification your telescope is currently being used at and the apparent field of the eyepiece being used. A 50 degree apparent field eyepiece being used at 100x give 0.5 degrees field of view. This is the same diameter as the moon in the sky.
  An eyepiece calculator is available for each of our telescopes and can be reached by clicking "View Item" in each telescope listing.

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Remember : Never look at the Sun with an unfiltered optical device or your naked eye.
It will result in blindness.