What Is a Reflector Telescope?

A reflecting telescope is an optical telescope that uses a combination of curved and flat mirrors to reflect light and form an image, rather than a refractive lens that uses lenses to refract or bend light to form an image.

use

A curved primary mirror is the basic optical element of a reflecting telescope and creates an image in the focal plane. The distance from the mirror to the focal plane is called the focal length (focal length), and negatives or digital sensors can be used to record images here, or eyepieces can be placed for the eyes to see. Although the mirror can eliminate chromatic aberration, there are still other aberrations:

• When using a non-parabolic mirror, there will be spherical aberration (imaging is not on a plane).

• Coma aberration

• Distortion (field of view)

Refractive reflectors are used in the design and correction of reflectors to eliminate some of these aberrations.

Almost all large astronomical telescopes used for research are mirrors for the following reasons:

• Under the use of a lens, the entire lens material must be free of defects and homogeneity without heterogeneity, and the mirror only needs to polish one surface perfectly, which is relatively easy to grind.

• Different colors of light will travel at different speeds as they penetrate the medium. For uncorrected lenses, this can cause chromatic aberrations specific to refractive lenses. It is expensive to make a large achromatic lens, and a mirror is completely free of this problem.

• Mirrors can study the spectrum over a wider range, but some wavelengths are absorbed as they pass through the lens of a refraction mirror or a folding mirror.

• Large-aperture lenses have technical difficulties in manufacturing and operation. One is that all materials will sag due to gravity. The lens with the highest observation and relatively heavy can only be supported around the lens. On the other hand, in addition to the reflective surface, the mirror can be on the back of the reflective surface and On the side.

While amateur astronomy is still using the design of Newton's focus, professional astronomy has tended to use the design of main focus , Kasai focus and Kud focus . In 2001, at least 49 reflecting telescopes with a diameter of 2 meters or more have adopted the design of the main focus.

Reflecting telescopes are divided into

Reflective telescopes have many advantages, such as: no chromatic aberration, can record celestial bodies in a wide range of visible light

Reflective telescopes have been widely used in astronomical observations. Because specular materials have no special requirements in terms of optical performance and no chromatic aberration problems, they can use large-caliber materials or multi-mirror lenses compared to refractive systems. Mounting technology, etc .; polished mirrors are generally coated with an aluminum film on the surface. The reflectivity of the aluminum film in the 2000-9000 Angstrom range is greater than 80%. Therefore, in addition to the optical band, the reflecting telescope is also suitable for near infrared and Research in the near-ultraviolet band; therefore, it is more suitable for stellar physics work (photometry and spectrometry of stars). Currently, large-aperture telescopes designed and constructed are reflecting systems. Unfortunately, the reflecting mirror surface of reflecting telescopes requires regular Coating, so its application in science telescopes is limited.