What can you see with a 262.5 times telescope?

First, the basic knowledge of astronomical telescope:

There are three kinds of astronomical telescopes: refracting telescope, reflecting telescope and folding reflecting telescope.

1. Refractive astronomical telescope is easy to use, with a large field of view and bright star images, but there is color difference, which reduces the resolution. The objective lenses of high-quality refractors are two double-separated achromatic lenses or three apochromatic lenses. But achromatic or apochromatic can't completely eliminate chromatic aberration.

2. The advantage of the mirror astronomical telescope is that there is no chromatic aberration, but the coma and astigmatism of the mirror are large, which makes the imaging quality at the edge of the field of view worse. There are two kinds of mirrors in common use: Newton type and Karl seglin type. The former optical system is simple and cheap, with a spherical reflector at the back end and an eyepiece at the front end; In the latter optical system, the primary and secondary mirrors are aspheric, and the primary mirror and eyepiece are behind, so the imaging quality is better and the price is more expensive.

3. The catadioptric reflecting telescope has the advantages of both a refracting telescope and a reflecting telescope: large field of view, good imaging quality, short lens barrel and convenient carrying. Compared with the refractive telescope with the same focal length and aperture, the price is less than one third. There are two kinds of catadioptric mirrors: Schmidt-Ka seglin type and Maksutov-Ka seglin type, the latter is also called Ma-Ka mirror. There are two kinds of horse mirror, three kinds. For example, the tube-wave BOSMA 1800 150 astronomical telescope and BOSMA2400200 astronomical telescope are all three-piece sets, which are deeply loved by astronomical enthusiasts at home and abroad because of their better imaging quality.

Second, reasonably choose the focal length of astronomical telescope

Choosing the focal length of an astronomical telescope is related to the celestial body you want to observe. If you want to observe nebulae and look for comets, you should choose a short-focus astronomical telescope; If you want to observe the moon and planets, choose a telephoto telescope; If you want to see binary stars, multiple stars, variable stars and star clusters, you'd better choose a telescope with a medium focal length. The medium focal length mirror can take care of both ends and is more popular. Usually, a short mirror means that the ratio of focal length to aperture is less than or equal to 6, and a long mirror means that the ratio of focal length to aperture is greater than 15, which is called a medium focal length mirror.

Third, the magnification of astronomical telescope is not as large as possible.

According to astronomers' long-term observation experience, the maximum magnification of astronomical telescope should not be greater than 1.5 times (in millimeters) of the aperture of the objective lens, and it should not be greater than 100 times when observed with a telescope with the aperture of 100 mm in a moderately quiet atmosphere. The best mute can reach 190 times; When the aperture is 200mm, and the atmospheric tranquility is moderate, it should not be greater than 170 times. The best quiet time can reach 340 times; In fact, for astronomy enthusiasts, the maximum magnification can reach 2 times or even 2.5 times (in millimeters) of the aperture of the objective lens when observing bright celestial bodies. However, the large magnification of astronomical telescope makes the image bigger and darker, and the jitter of the atmosphere is also amplified, which makes the image more blurred.

Four, according to the individual's economic ability, as far as possible to choose a large-caliber astronomical telescope.

1, larger aperture, more light energy received, and darker celestial bodies can be observed;

2. The larger the aperture, the greater the maximum effective magnification V, because V= the aperture d of the primary mirror (in millimeters);

3, large aperture, high resolution, can observe more planetary details, can distinguish binary stars, and may even find darker asteroids and comets. Theoretically speaking, resolution is only related to aperture, but in fact it is related to optical design, processing, assembly and calibration. The resolution of general popular science telescope can reach twice the theoretical resolution angle, even if it is a high-quality telescope, while the resolution of tube wave BOSMA 1800 150 is better than 1 ",which is close to the theoretical value.

Five, how to distinguish the optical quality of popular science astronomical telescope:

When buying during the day, you can use an astronomical telescope to observe a distant building and move the outline of the building to 1/4 of the field of view. If the outline is orange, yellow or blue-purple, or the outline is particularly curved, don't buy it. Look at the leaves in the distance. Generally speaking, a 60 mm telescope can see Ye Jin 40 meters away. Don't buy things that you can't see clearly. Of course, the larger the aperture of an astronomical telescope, the farther you can see. The tube wave BOSMA70060 astronomical telescope (60 mm in diameter) can clearly see Ye Jin 85 meters away. You can watch the stars at night. If the stars you see are colorful, especially obvious, or the stars at the edge of the field of vision are dragging their tails, which are twice as long as the stars, this kind of astronomical telescope is not suitable for astronomical observation.

Six, astronomical telescope resolution ability (resolution) detection.

The best way is to observe binary stars. For example, the π star in Aquila is a binary star (close to Altair) with an angular distance of1.4; Aries ε star is a binary star with an angular distance of1.5; Cygnus delta star is a binary star with an angular distance of 2 ".1; Auriga is a binary star with an angular distance of 3.0; Leo's gamma star is a binary star with an angular distance of 4.3.

Seven, about the observation of the planet

When observing gold, wood, water, fire and Saturn, the required magnification is that the planetary small circle in the field of view of the astronomical telescope is the same as that of the full moon seen by the naked eye (3 1 angular minute). So Jupiter can be observed with a 50 mm objective lens, Venus and Mars can be observed with an 80 mm objective lens, and Mercury can be observed with a 280 mm objective lens.

Eight, about the observation of sunspots

Large sunspots can be seen with a small telescope, and some small sunspots can only be seen clearly with a large telescope. Amateur observation of sunspots generally adopts projection observation. To observe the sun and the moon, it is necessary to use a smaller telescope of aperture ratio (D/F), preferably 1: 15 ~ 1: 20. You can also add an aperture in front of the mirror to reduce the aperture ratio. However, this will reduce the resolution of the telescope.

Nine, about the observation of the moon

The moon has craters, chain mountains, moon sea, moon valley, furrows (dry rivers) and bright radiation zones. A good telescope can see very fine details on the moon. The best magnification for observing the moon is (1 ~ 1.5) × the aperture of the main mirror (mm).

Ten, about astronomical telescope bracket

There are two kinds of astronomical telescope supports: the horizon type and the equator type, both of which have two vertical rotating shafts. The field of view of astronomical telescopes is generally small, and the larger the magnification, the smaller the field of view, so choose a bracket that will not shake due to the wind.

I. Problems and suggestions

As a student, or a salary enthusiast, or even a few astronomy enthusiasts who "get rich first", they will be dazzled when choosing a telescope, especially when they face the terms aperture, focal length and coating for the first time. At this time, the best way is to join the local astronomy enthusiast organization first, so that you have the opportunity to actually use the telescope in other people's hands before making a decision according to your own needs. Before buying a telescope, you should also carefully consider the following questions:

1. How much energy and time are you going to spend getting familiar with the sky? If you are familiar with the night sky and the celestial bodies to be observed, and don't find it hard to look for the stars in the star map, then you can choose a telescope that is cheaper, more portable, lighter and better to use. On the contrary, those telescopes with precise coordinate mechanisms or even computer-controlled automatic star searching will be the best choice. It should be noted that with the development of electronic industry and the advantages of large-scale production, the prices of fully automatic telescopes of major telescope manufacturers in the world are becoming more and more reasonable, which is by no means unattainable.

2. How far is your observation place? How to carry your telescope and how much labor are you willing to pay when carrying it? The answer to this question not only determines the aperture of the telescope, but also relates to the optical structure of the telescope. Please remember a conclusion that countless astronomy enthusiasts have paid a lot of money, that is, the frequency of telescope use is inversely proportional to its weight. We think that a telescope that is often taken out for observation is far better than those that are too heavy to stay at home.

3. What accessories do you want? Most modern telescopes have diverse functions and countless accessories, but only a handful are used in actual observation (at least often used). We found that most enthusiasts, including the author, like the "basic" telescope, and the benefits brought by too many functions and accessories are far less than the economic burden they bring you.

4. Are you going to take celestial photography or CCD imaging? Both "astrophotography" and "CCD" are very expensive, and beginners usually need several telescopes and several years to build satisfactory equipment and get satisfactory results.

The most important parameter that determines the performance of a telescope is the aperture. The larger the aperture, the darker the celestial body you can see and the more details you can distinguish. But caliber is not everything. A telescope with poor workmanship can't achieve its performance or even work. Fortunately, the caliber used by enthusiasts, whether optical or mechanical, is not difficult to process. As long as the general manufacturers take it seriously, they can produce satisfactory products. But occasionally there will be some unqualified products. Fortunately, the consumer protection law has been deeply rooted in the hearts of the people. As long as we find it in time and insist strongly when necessary, replacement or return is not a problem.

Different optical structures make the telescope have different optical properties. Schmidt-Ka seglin, Newton reflector and various refractors all have their own advantages and disadvantages, which lead to the difference of optical performance, but this difference is secondary to the difference of aperture. We can think that the optical performance of telescopes with the same caliber and the same technology level should be close, but the quality difference caused by different processing levels is really huge.

In addition, the astronomical atmosphere will affect the telescope's ability to distinguish details, and the brightness of the sky background will affect the telescope's ability to observe dark objects. Visual objects have a great influence on large-aperture telescopes. If you observe in a place with bright sky background and poor visibility, such as a big city, there is no need to move out a large telescope. If you keep observing in such a place, you don't need to buy a large telescope.

Generally speaking, modern high-quality refractors have the best optical performance per aperture, but they are also the most expensive compared with other types of telescopes. In addition, when the aperture exceeds 10 cm, the lens barrel is usually too long to carry (of course, APO refractor is not included). Schmidt-Ka seglin and Maksutov-Ka seglin folding reflecting telescope have the best portability, but these telescopes are still expensive. From the optical performance alone, Newton mirror, especially Dobson Newton mirror, has the highest cost performance (not optical quality). Their portability is better than that of refractors under the same aperture (because their relative aperture can be made very large), but it is obviously not as good as that of catadiopters.

Two. About telescopes

For beginners, ordinary refractometers with small aperture (less than 10 cm) are the best choice. They are very cheap (compared with catadioptric mirrors and APO refractors) and simple to operate and maintain. It is suggested that if economic conditions permit, you should try to buy regular astronomical telescopes. "Conventional" refers to the standard eyepiece interface with excellent optical quality (the most commonly used interface at present is 1.25 inch). At present, the low-grade refractors (mostly 50-60 mm in diameter) on the market are uneven in quality, and most of them have defects in design and manufacture. It is best to ask an expert telescope to help the staff when purchasing.