How do astronomical telescopes find the moon and Saturn?

The moon has obvious goals at night, so it doesn't need to look for them. You can see the crater with an astronomical telescope.

For Saturn, first prepare a planet map of the month and find out the approximate location. Saturn is red and yellow, and it is also very bright and obvious.

First, about astronomical telescopes;

Astronomical telescope is an important tool for observing celestial bodies. It is no exaggeration to say that there would be no modern astronomy without the birth and development of telescopes. With the improvement of telescope performance in all aspects, astronomy is also experiencing a huge leap, which rapidly promotes human understanding of the universe.

Second, the classification of astronomical telescopes;

1, 1. Refractive astronomical telescope

The so-called refractive astronomical telescope is a kind of telescope with a lens, which focuses the light of distant objects and presents a real image. As an objective lens, it refracts the distant light and focuses it on the focus.

Refractive astronomical telescopes are divided into two types:

(1) galileo telescope;

The first astronomical telescope used a concave lens as an eyepiece, and the image seen through the telescope was the same as that seen directly with the eyes. The surface of the earth is convenient, but it can't expand the field of vision. At present, this design is no longer used for astronomical observation.

(2) Kepler telescope:

Using a convex lens as an eyepiece, all refractive telescopes are of this type now, and the imaging is up, down, left and right, but it has no effect on our celestial observation, because the eyepiece is a convex lens, and more than two lenses can be put together to expand the field of vision, which can improve the aberration and eliminate the chromatic aberration.

2. Reflective astronomical telescope;

Reflective astronomical telescopes use a concave mirror called a primary mirror instead of an objective lens. There is also a small mirror called the secondary mirror, which reflects the light collected by the primary mirror to the outside of the lens barrel, and the light image reflected by the secondary mirror is amplified by the eyepiece. The biggest advantage of reflection type is that because the main mirror is a mirror, the light does not need to pass through the glass, so there is no chromatic aberration at all, and it is unlikely to absorb ultraviolet light or red light, which is very suitable for physical observation such as spectroscopy. Although there is no chromatic aberration, there are other kinds of aberrations.

At present, the two most common reflective telescopes are:

(1) Newton astronomical telescope;

1668 was invented and designed by Newton, which consists of a parabolic primary mirror and a planar secondary mirror. The plane secondary mirror is installed slightly in front of the focus of the light reflected by the primary mirror, and forms an angle of 45 degrees with the optical axis (as shown in the above figure). This structure is the simplest and the image contrast is high, which is also the choice of most people. Usually the focal ratio is between f4 and f8.

(2) seglin Astronomical Telescope:

Using a hyperboloid as a secondary mirror, the light is focused in front of the main focus, passes through a round hole of the main mirror, and focuses behind the main mirror. Because after a reflection, the lens barrel can be shortened, but the field of view is narrower, the astigmatism is more serious than Newton's, and there is a little field curvature.

3, catadioptric astronomical telescope:

The kind that uses the advantages of reflection and refraction, basically like reflection, also has the disadvantages of reflective astronomical telescope. In order to eliminate the comet aberration whose field of view deviates from the optical axis, a lens is used, and the main mirror is a spherical mirror, which is easier to grind than the reflective one.

The reflecting and refracting telescope is Schmidt-Card telescope;

Astrography was invented by Schmidt in 1930. A spherical concave mirror is mainly used as the main mirror to eliminate coma, and an aspheric lens placed in a proper position in front of the main mirror is used as a corrector to correct the spherical aberration of the main mirror. In this way, a wide-angle field of view (up to 40-50 degrees) can be obtained, without spherical aberration and coma, which are common in general mirrors, only slight chromatic aberration produced by the correction mirror. Schmidt telescope for photography can achieve a very small focal ratio (generally between f 1 and f3, and the lowest can reach "0.6"), so it is very suitable for star field and nebula photography.