Field of view is measured in degrees, which is the same way that we gauge angular distance in the sky. The apparent field of view is the view through the eyepiece alone. The apparent field of a 50 degree eyepiece is bigger than the field of a 30 degree eyepiece. If the apparent field is large, the true field is also comparatively larger than an eyepiece of the same focal length with a smaller apparent field. The same 26mm Plossl eyepiece, placed in a telescope with a focal length of 2032 mm, would have a magnification of 78x, and a true field of view of 0.64 degrees.
Amateur astronomers use several handy techniques to determine distances in the sky.
The distance between the two pointer stars in the end of the Big Dipper is about 5 degrees. A fist, held at arm's length, is about 10 degrees wide. Three fingers at arms length, are about 5 degrees wide. The full moon is about a half a degree wide. Return to the top of this page .