How Telescopes Work


Finders are devices that help aim the telescope at its target, similar to the sights on a rifle. Some finders come standard on telescopes, while others are sold separately. Finders can come in three basic types:

  • Peep sights - notches or circles that allow you to line up the target
  • Reflex sights - a mirror box that shows the sky and illuminates the target with a red LED diode spot, similar to a laser sight on a gun
  • Telescope sight - a small low magnification (5x to 10x) telescope mounted on the side with a cross hair reticle, like a telescopic sight on a rifle

Peep sights are inexpensive, but tend to be less precise for finding objects. Reflex sights do not magnify objects, but rather present a naked-eye view of the sky. They have become popular because they are easy to use and vary in price from $40 to $60. Telescope sights magnify the sky, but present an upside-down image, which can make them difficult to use. They come in one- or two-ringed sights (the rings are used for aligning the sight with the telescope). When given the choice, take the two-ring sight. Telescope sights can range from $15 to $50.