A very popular system is the Schmidt-Cassegrain telescope design. Many amateurs swear by these telescopes as they are both very compact and easy to transport. They provide a very short tube length together with a long focal length. A primary mirror with a central hole throws back the incoming light and starts to focus it. The light then strikes a secondary mirror, which reflects the light back again, with it finally passing through the central hole into the focuser at the back of the telescope. A Schmidt plate is mounted at the front for correction. The Schmidt-Cassegrain design can be described as a true all-round telescope as you can do with virtually everything with it. Nevertheless, this telescope does have some disadvantages: The small aperture ratio, of 1:10 or less, means that type of telescope for excellent for visual observing. However, if you want to take photographs with it, you will encounter problems due to this low aperture ratio: The telescope will need to be tracked at high precision.

The Schmidt plate protects the interior from dust and other contaminants. However, in such closed systems the cool-down time - until the telescope has adapted to the outdoor temperature – can be relatively long.
The long focal length also produces a relatively small field of view. A Schmidt-Cassegrain telescope also has the drawback that it shows field curvature. There may be some edge blurring in photography. Other aberrations are so small that they remain within the diffraction disk and are not noticed.

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