Sekundääripeilin

Sekundääripeilin, often referred to as a secondary mirror, is a crucial component in many reflecting telescopes. Its primary function is to redirect the light gathered by the main mirror, the primary mirror, towards the eyepiece or imaging sensor. In most common telescope designs, such as the Newtonian reflector, the secondary mirror is positioned at an angle, typically 45 degrees, within the telescope tube. This angled placement intercepts the converging light cone from the primary mirror and sends it off to the side, where it can be observed without obstructing the incoming light.

The size and shape of the secondary mirror are carefully calculated to be just large enough to intercept all the light from the primary mirror that reaches the focal plane without introducing significant obstructions or aberrations. Too small a secondary mirror will cause vignetting, darkening the edges of the field of view. Too large a mirror will block more light than necessary, reducing the telescope's brightness and potentially causing diffraction effects.

Secondary mirrors are typically made of highly reflective materials like aluminum or enhanced aluminum coatings to maximize the amount of light reflected. They are held in place by a spider, a structure of thin vanes that extends from the telescope tube's inner wall. The design of the spider is important to minimize diffraction spikes, which are star-like rays that can emanate from bright objects in an image due to the obstruction of light by the spider vanes. In some telescope designs, like Cassegrain reflectors, the secondary mirror is convex and reflects the light back down through a hole in the primary mirror, allowing for a more compact telescope tube.