CASSEGRAIN REFLECTOR

Figure 19-11b shows the design of the cassegrain reflector. The eyepiece mirror is mounted closer to the objective than it is in the newtonian design. It is not angled, but it is convex. The convexity of this mirror increases the effective focal length of the objective mirror. Light reflects from the convex mirror and passes through a small hole in the center of the objective containing the eyepiece.
The cassegrain reflector can be made with a physically short tube and an objective mirror with more curvature than that of a newtonian telescope having the same diameter. As a result, the cassegrain telescope is less massive and less bulky. Cassegrain reflectors with heavy-duty mountings are
physically stable, and they can be used at low magnification to obtain a wide view of a large portion of the sky.

Fig. 1. The newtonian reflector (a) has an eyepiece set into the side of the tube. In the cassegrain reflector (b), the eyepiece is in the center of the objective mirror.

مواضيع ذات صلة

Mirror reflections

The sensation of color

Physiochemistry of color vision

The mechanism of color vision

The chromaticity diagram

Measuring the color sensation

Color depends on intensity

Aberration

The ω,k four-vector

Moving sources

Anomalous refraction

The intensity of reflected light