It is possible to vary the focal lengths of objective and eyepiece from 0.05 m to 0.5 m by using the text fields of the panel (don't forget to press the "Enter" key!). In addition, you can modify the direction of the rays by dragging the mouse. The program will calculate for both objective and eyepiece the angles between the rays of light and the optical axis (marked with blue and green colour) and the magnification. As an example, the applet shows the six brightest stars of the Pleiades, viewed with the unaided eye (bottom left) and through the telescope (bottom right).
The magnification of the refracting astronomical telescope can be obtained with the following approximate formula (for small angles):
|v = f1 / f2|
v .... Magnification f1 ... Focal length of the objective f2 ... Focal length of the eyepiece