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How Aperture Works

Telescopes and Aperture
The bigger the aperture, the better a telescope can magnify stars, planets and other distant entities.
The bigger the aperture, the better a telescope can magnify stars, planets and other distant entities.

Telescopes rely on the principles of aperture to help people see far-off objects in space. Image quality and magnification all start with the aperture, which is very different from the kind found in cameras. Telescopes have two basic jobs -- to collect light and to magnify images. That second job depends entirely on the first, so in order to build a quality telescope, a manufacturer ensures that the device can gather as much light as possible. A larger aperture means the scope has more light-capturing potential.

With telescopes, the term aperture doesn't refer to an opening as it does in cameras. Aperture indicates the diameter of the main optical element, which is either a lens or a mirror. As the aperture size increases, more light enters the scope, making your target objects appear brighter. This results in better visual information for your eyes and means that you can see fine details and faint objects in space that a telescope with a smaller aperture would miss. Thus, provided it's made with high-quality construction methods and materials, a large-aperture telescope creates superior magnification and extremely sharp details.

You can change a telescope's magnification power by using different eyepieces. However, unlike cameras, telescopes don't have adjustable aperture settings. Telescopes come with just a single aperture size, which will be listed on the specifications. Telescope aperture sizes are generally listed in inches or millimeters. Three-inch (76.2mm) telescopes are much less expensive than 8-inch (203.2mm) versions simply because larger apertures are harder to manufacture.

Whether you're gazing far into space with telescopes or taking snapshots of the anthills at your feet with a point-and-shoot camera, aperture plays a major role in how those images appear to your eyes. Now that you have an understanding of how aperture affects visual characteristics, you can see your world (and others) in a whole new way.