Intimate with the stars | 'Contact' | How to choose astronomical telescope
On a hot summer day, the deep Milky Way stretches in the sky. You who like the stars, you may want to have an astronomical telescope to achieve a closer 'contact' with the stars. So, what kind of astronomical telescope is more suitable for the first into the astronomical circle? What about you?
Balanced cost and portability, refraction is the first choice for entry
In the long years of the birth and development of human civilization, most of the time is to observe and explore the world with the naked eye. But our eyes are not as strong as imagined, because the pupil is small, in a dark environment The ability of the eye to identify objects is very poor, which affects humans' deeper exploration of the starry sky and becomes a bottleneck for understanding and understanding the universe. Until 1609, the Italian astronomer Galileo first pointed the telescope at the sky, and the astronomical telescope was born. Human civilization has also opened a new page.
What is an astronomical telescope? If you ask this question to an astronomer, the answer may be 'Keck' 'VLT' 'Subaru', a professional telescope with a few meters of diameter. In fact, as long as it can be pointed to the sky, it can You see that a telescope of a celestial body is an astronomical telescope. This of course includes both large astronomical telescopes used by astronomers, as well as small portable telescopes and binoculars used by astronomers.
The structure and basic principle of telescopes used by astronomy enthusiasts are very simple. Astronomical telescopes can be roughly classified into refractive telescopes, reflective telescopes, and transflective telescopes according to the type of optical system. These three types of telescopes can be accessed by astronomy enthusiasts. But most people's first telescopes are refracting telescopes.
A refracting telescope is a telescope that achieves magnification by combining two or more lenses. Its basic principle is not fundamentally different from the telescope used by Galileo more than 400 years ago. The simple structure means lower cost and good portability. Sex, so it is the first choice for entry-level astronomy enthusiasts.
Don't ask the magnification again, the caliber is the most important.
In the face of an astronomical telescope, the first reaction of many people is how many times it can be amplified. In fact, the magnification is not a parameter describing the quality of the telescope. Because it is related to itself, it is also related to the detector at the back end. When the human eye is used as a detector, the telescope must be equipped with an eyepiece to achieve observation. With different eyepieces, the telescope can also obtain different magnifications.
There are two important parameters of the telescope, namely the aperture and focal length. The diameter refers to the diameter of the largest beam that the telescope objective can receive. For a common refractor, it can be simply understood as the diameter of the front circular main lens. The focal length is from The distance from the main point of the telescope optical system to the main focus, its value will be marked on the mirror together with the aperture. The magnification is actually obtained by dividing the focal length of the main mirror by the focal length of the eyepiece. Dividing the focal length of the telescope by the aperture, you can also The focal ratio is the same as the aperture of our commonly used camera lens, reflecting the telescope's light collecting ability. The smaller the value, the better.
The appearance of astronomical telescope is to make up for the deficiency of the human eye. Because the pupil is small, the resolution of the human eye is very low, we can not distinguish the sunspots on the sun, the craters on the moon, the moons of Jupiter, etc. To the faint celestial body, under the ideal conditions, the darkest eyes of the human eye can only see stars of about 6.5. The two problems of 'visible' and 'clearly clear' are solved by the telescope, but actually decided These two capabilities are the diameter of the pupil, which is equivalent to the diameter of a telescope. The larger the diameter of the telescope, the theoretically observable darker objects, and the two points within a smaller angular distance. When choosing a telescope, caliber is the most important and even the only basic parameter to consider.
Select the telescope as needed, and also have a pair of 'good saddle'
The larger the aperture, the higher the price of the telescope must be. If you just want to buy a telescope to visually observe, you can not pursue a large caliber. If a refractor telescope has a diameter of more than 150 mm, the price will be high. Secondly, it will be big and heavy, and the portability will be greatly reduced. The refraction telescope from 80mm to 100mm is more suitable for familiarizing and carrying out the first-order astronomical observation. The price is mostly less than 2,000 yuan.
If you want to observe some advanced targets, such as the details of the surface of the planet, you need a telescope with a larger aperture and a longer focal length. Reflective and transflective telescopes are a better choice. In contrast, this The lens barrels of the two types of telescopes are shorter than the refraction telescopes of the same focal length, which are easy to carry and carry.
The next step is to perform astrophotography. Any type of telescope needs a good optical system quality. Usually, the telescope for astrophotography is not necessarily large, but it costs thousands of dollars. , expensive to tens of thousands to hundreds of thousands of yuan.
When buying a telescope, you not only buy a main mirror, but also its support, and the equatorial mount that controls its rotation in both the right ascension and declination. The bracket is in most cases a tripod, which serves as the support for the entire telescope. System, its role is very important.
As for the equatorial mount, the functional requirements vary greatly. The most basic equatorial mounts only have manual adjustment functions, and the workmanship is rough. The price can be as low as several hundred yuan. Some equatorial instruments have excellent workmanship and electric tracking. The price is generally in the thousands of dollars. Some of the higher-end equatorial meters can accurately adjust the polar axis, achieve high-precision tracking, and have the function of extending the guide star and other functions, the price can reach tens of thousands of yuan. For ordinary visual observation of the telescope, The equatorial mount and tripod that are usually matched with the main mirror can meet the demand. If you have already started a good telescope, you must have a good saddle for the good horse.
'Artifact' binoculars, can watch the show and see the stars
There is a very common type of telescope that can be applied well to astronomical observations, that is, binoculars. As the most preserved telescope in the market, binoculars can be used not only in watching performances, but also in sports competitions. In the astronomical observations show their talents.
Most binoculars that everyone can access are refracting telescopes. The biggest feature of binoculars is that they are portable and can be easily pointed in a certain direction, so the operation is simple. For astronomical observations, binoculars are also There is a very important advantage. Although most binoculars are not high magnification, they will have a large field of view, which means that you can get a larger field of view than other telescopes. This is for many types of astronomy. Observation is very important.
Binoculars are of course the larger the better, but the choice should also take into account its field of view. If you can do the best of both worlds, such binoculars must be more expensive. Considering its wider application, it is recommended to buy a good one. Some binoculars.
The aperture, magnification and field of view of the binoculars are generally marked on the mirror. The caliber and magnification are represented by two sets of numbers. For example, '10×50' means that the magnification of this binocular is 10 times, and the aperture is 50 mm; another example, '15~40×60' means that the magnification is adjustable between 15 and 40 times, and the aperture is 60 mm. The field of view is another important indicator reflecting the performance of binoculars, but it is generally not 'degree' is given in units, but is expressed by 'maximum width of the scene that can be seen at 1000 meters or 1000 yards'. For example '130m/1000m' or '400Ft./1000Yd.' means using this pair The barrel mirror can see a maximum width of 130 meters or 400 feet at 1000 meters or 1000 yards.
Author: Li Xin