What astronomical telescope is good?

Practical Teaching and Operational Guide for Choosing Astronomical Telescopes Every amateur who loves astronomy and stargazing probably has both "hope" and "desire" and "extravagant hope" to own astronomical telescopes. His eyes pop out every time he sees the new telescope in the astronomy magazine! But there are so many kinds of telescopes, even if the budget is sufficient, it is impossible to buy everything (er … I really want to do this)! How to choose the right telescope? I believe this is a question in many people's minds! Since there is a problem, let's answer it!

A complete telescope consists of a lens barrel and a bracket. The lens barrel part refers to the telescope itself, which has three types: refractive, reflective and catadioptric. The platform part refers to the part that carries the telescope, and there are two kinds of theodolite and equatorial instrument. Because the telescope is the key to obtain celestial images, this paper only discusses the telescope part. A telescope-no matter what kind of telescope, the most important thing is the size of the aperture, because the aperture of the telescope determines all the capabilities of the telescope. The "performance" of a telescope determined by its aperture includes: a) focal ratio, b) focusing, c) resolution, d) extreme magnitude, e) weight and f) price. e

A.) Focal ratio: Focal ratio refers to the ratio of the focal length of a telescope to the aperture, f = f = F=f/d d, and this ratio is the aperture on the camera lens. If the focal length is inconvenient, the larger the telescope aperture, the smaller the focal ratio and the brighter the image. The focal ratio has a great influence on astrophotography, because if the focal ratio is twice that of others, it means that your exposure time is four times that of others. For example, if the optical system exposure of f/2 is 1 sec, the correct exposure can be obtained, then the optical system of f/4 needs to be exposed for 4 seconds to have the same image density. seven

B) Light concentration: Light concentration refers to the ratio of the light collected by the telescope to the light observed by naked eyes. When normal people's pupils are fully opened, the diameter is about 7 mm. Compared with the naked eye, the aperture area of 70mm telescope is 702/72= 100 times, that is to say, the light collection capacity of 7 cm telescope is 100 times. The larger the aperture of the telescope, the stronger the light collection ability, and the darker the celestial bodies that can be seen, which is also the reason why the telescope is getting bigger and bigger. C.) Resolution (θ): The larger the magnification of the telescope, the larger the image you see, but it may be unclear when the image becomes larger. The clearest detail that can be seen within the scope of a telescope is called resolution, which is measured in angular seconds. The formula is θ = 116 "÷ d (mm), so a telescope with a diameter of 1 16mm can just distinguish the details of the1"distance, but it is not clear if it is closer, and the multiples are mostly the same. D.) Limit magnitude (M): The darkest magnitude that a telescope can see is called the limit magnitude. People with normal vision can see the sixth star in the darkest place in the dark and transparent air. The light collection ability of a telescope with a diameter of 70mm is 100 times that of the naked eye, so they can see the sixth star which is five stars darker than the sixth star. The aperture of the telescope is much larger than that of the naked eye, so it can naturally see darker magnitude. The formula for calculating the limit magnitude is M= 1.77+5. For example, for a telescope with a diameter of 70mm, the limit magnitude is m =1.77+5 ㏒ 70 =11.0 (and so on. ). e) Weight: Take a refracting telescope as an example, doubling the aperture of the objective lens means that the weight of the objective lens is at least quadrupled. The larger the aperture of the telescope, the heavier the objective lens, so it is necessary to support the lens with a stronger lens holder. At the same time, the larger the aperture, the larger the relative volume of the lens barrel, and the lens barrel must be stronger and stronger. The result may be a telescope that the equatorial telescope cannot carry! In order to lose weight, we were forced to sacrifice the strength of the lens barrel, which was not worth the loss. F.) price: actually, this is not called performance, but the result. It is mentioned in the item "e) weight" that doubling the aperture of the objective lens means that the weight of the objective lens has increased by at least four times, but the price will definitely exceed four times. But there's no need to be so sad. The problem of weight and price is not so serious on a reflective telescope! Therefore, in fact, reflective telescopes are also a good choice.

After reading these instructions about telescopes, do you have a better idea of choosing a telescope? If not, it doesn't matter. We'll tell you directly now who should buy what kind of telescope. `

A.) The entry type is the same:

In fact, the so-called entry-level hobby is the most difficult to answer! For example, I recommend a small telescope to a beginner. As a result, this fellow is addicted to playing and will spend money on a large telescope. The conclusion is that this small telescope may be a waste of investment. On the contrary, isn't it a greater waste to recommend a bigger telescope at first and stop playing after a while? ! So it is difficult for beginners to recommend which kind of telescope to buy. To sum up this problem, it is the same as the introduction of "the heart doesn't belong to it yet" The principle of choosing a telescope is as follows: the refractor is mainly APO—— with a diameter of 6 ~ 8 cm-this specification is recommended because if you want to buy a larger telescope, this small one can also be used as a guide star; And if you don't play, the loss of selling will not be so great. Reflector 10 ~ 15 cm Newton mirror is more suitable-because Newton mirror is much cheaper, it will not be uncomfortable in case of use. As for the equatorial plane, it depends on whether the budget is enough-I don't recommend this type of impulsive enthusiasts to buy the equatorial plane. * Author's recommendation: FS-78, VIXEN FL-80S, Pentax 75SDHF, Borg 75ED produced in Gao Qiao. H

FC-60 made in Gao Qiao, MT- 130 made in Gao Qiao, VIXEN R- 150. f

B) The same is true for the introduction to eye vision: "The purpose of buying binoculars is just to see with your eyes! This hobby should give priority to the comfort of the eyes, so the eyepiece should be the most important consideration. As far as the telescope is concerned, because it needs to be seen with the eyes, and the analytical ability of the naked eye is not as good as that of the new observation instrument, the larger the aperture of the telescope, the better, "for the naked eye to see"!

The principle of choosing this kind of telescope is that the lower limit of refractor is 10 cm, the focal length is longer, and the focal ratio (f) is above 8, so it doesn't matter whether APO grade is required. For the reflector, the aperture should not be less than 15cm, and the focal length should be longer. In fact, the most worthy choice is the Schmidt-seglin telescope (SCT), which is not only more than 20 cm in diameter, but also has good eye quality and low price. It is a very suitable entry-level eye telescope. three

The telescope suitable for this type is not a small machine in terms of weight and volume. You can consider buying an equatorial telescope to carry with you for easy observation.

* Author's recommendation: MEADE LX-50-200, CELESTRON SC-235L, CELESTRON SC-203L, Vixena-120SS. 6#T

C.) Introduction to Sun and Moon Photography:

Seeing astronomical photos taken by others, you must envy and hate, so you also want to take some good photos to tell the world and share them with your relatives and friends. To be honest, I don't welcome all my colleagues who want to step into astrophotography to compete with me for jobs ... er, no, no-yes, I don't even suggest ... er, no, no, what I really mean is that it is difficult to take astronomical photos, the success rate is actually not high, and the investment is huge. Therefore, if you want to step into this field, you must have a complete evaluation and consideration in advance, and you must not rush into it. t

I just want to start celestial photography, so I suggest starting with the sun and the moon ... well, start, because they are the best, the easiest to succeed, the least laborious and the least expensive (well! This is the most important thing).

It is enough to shoot the sun with a refractor below 8 cm, and the focal length is longer, and the focal ratio is above 8 or even 15, preferably APO level. Of course, the bigger the aperture, the better, but the strong light and high heat of the sun are not easy to overcome. The bigger the aperture, the more serious the problem, so most people who like to shoot the sun only use the aperture of 5 cm. Few people shoot the sun with a mirror because of the air flowing in the pipe-unless they use a vacuum solar telescope (it's too difficult! )。

The situation of shooting the moon is similar. The size and brightness of the moon allow small telescopes to work. Of course, the bigger the aperture, the better However, unless you want to photograph a small hole or a small part on the moon, an APO-class refractor with an aperture of 10 cm or less and a focal length ratio of about 8 is enough. Reflectors are also a good consideration. 13 ~ 16 cm is the appropriate aperture size, and the longer the focal length, the better. Newton mirror is recommended.

* Author's recommendation: FS-78, VIXEN FL-80S, Pentax 75SDHF, Borg 75ED produced in Gao Qiao.

FS- 102 made in Gao Qiao and MT- 130 made in Gao Qiao.

D) Intermediate eye vision is the same:

If you devote yourself to astronomical science and find yourself unable to extricate yourself, but you don't want to or can't take pictures, it's actually a good thing to be an eye-catching astronomical observer.

At this stage, we can't just "watch", we must try our best to make records and make the observation time meaningful. For example, observing and recording the changes of cloud bands on Jupiter's surface for a long time, or being familiar with the positions of various bright objects in the sky, etc.

If you want to see with your eyes, the aperture of the telescope should not be too small. After all, the ability of the human eye can't compare with the new observation equipment. However, the larger the diameter of the telescope, the greater the price change, so choosing a cheap big bowl telescope has become the most important thing.

The most preferred telescope is a Dobson reflector with a diameter of more than 25 cm. The so-called Dobson telescope is to put a Newton-shaped mirror with a short focal length (the focal length ratio is usually about 4) on a stand that directly falls to the ground. Because the structure is extremely simple, the price is relatively very cheap. The 40cm Dobson telescope is much straighter than the13cm APO refracting telescope. Another telescope that can be considered is the Schmidt-Gesellschaft telescope (SCT) which is more than 25cm. Thanks to the mass production of the machine, this telescope also has the characteristics of large aperture and low price, which is very suitable for human observation. As for the refractometer, because the large aperture refractometer is very expensive, achromatic color above 15 cm can also be considered if it can be supported in the budget.

* Author's recommendation: MEADE DOB-40, CELESTRON C- 1 1, μ-2 10 made in Gao Qiao. :C 1^

E) Intermediate photography hobby: This hobby is the largest population group in amateur astronomy in Taiwan Province Province at present. A new generation of amateur astronomers in Taiwan Province Province also have the same hobby. Due to the influence of Japanese astrophotography, most of them have devoted themselves to the field of astrophotography, which is not bad, but everyone is rushing to take pictures, and few people do anything else.

Equipment is an extremely important factor in taking good photos. For beginners, the "construction cost" of equipment at this stage is extremely amazing. I think it will be a great frustration to buy this level of equipment to take pictures as soon as I get started. Therefore, novices must have a solid astronomical foundation and skilled telescope operation in order to evaluate whether to "jump into the fire pit".

Subdivide the subjects at this stage, which can be further divided into:

E 1。 ) specializes in shooting the sun. To photograph the sun, strict and effective dimming is very important. If this can be done, the APO-class refractor with a diameter of 10 cm is a good choice. Another requirement as far as possible is that it is best to have a considerable degree of black and white darkroom ability. Few people shoot the "colorful" sun, and I think the resolution of the film may be the biggest reason. After all, the resolution of color negative is not as good as the special professional black-and-white film.

E2。 ) Specially shoot the moon and planets: Both the moon and the planets are shot by magnifying photography, so the telescope should have a large aperture and a long focal length. Newton reflector with a diameter of 20 ~ 30cm and a focal ratio of 6 ~ 10 or classic geyser green reflector is a good choice because of its low price but high quality. As for the refractor, 15 ~ 20 cm APO refractor is the limit of personal ability due to the limitation of price, weight and volume.

E3。 ) Specially shoot nebula clusters: Nebula clusters are celestial bodies deep in the sky with the characteristics of small area and low brightness. Therefore, to photograph nebulae and star clusters, the focal ratio of the telescope should be as small as possible. The best equipment is a Schmidt camera with a caliber of more than 20 cm. This is a special kind of telescope, which can only take pictures, but can't be seen with eyes. The focal ratio is generally below 3, which is very bright. Then there is the 10 ~ 15 cm APO refractor, which has the advantages of excellent contrast and sharp imaging, and the focal ratio is selected below 6. The last choice is a Newton-type bull's-eye lens with a diameter of 20 cm and a focal ratio of less than 5. No matter what you want to shoot, a mobile, stable and accurate equatorial camera is a necessary equipment. Choosing a good equatorial telescope will not be easier than a telescope. Limited to the topic of this article, it is not discussed here. Please consult your senior colleagues if you are interested.

Intermediate astrophotography is as good as others, most of them are shot with cameras and negatives, while black and white negatives are better than color negative in some aspects, so it is good to have a considerable degree of black and white darkroom ability.

* Author's recommendation: E 1. ) pentax 105SD, FS- 102, VIXEN FL- 102S, Gao Qiao.

E2。 ) MT-200 made in Gao Qiao, FS- 128 made in Gao Qiao and μ-250fc made in Gao Qiao.

E3。 ) Borg 125ED, Pentax 105SDHF, Wicksen ED-114SS.7G9J.

F.) The higher-order eye vision modes are the same:

Higher-order vision is the same. In my classification, there is only one thing to do-comet search. After you have passed the naked eye observation test of hundreds of nebulae and clusters, keep in mind the distribution of all celestial bodies in the whole sky. What else can you see at this time? Just to see if there are any new celestial bodies. The efficiency of eye search for supernovae is too poor, so we can only do comet search.

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To do comet search, the first recommendation is the super-large caliber binoculars. /kloc-Refractive binoculars with a diameter above 0/2 cm are ideal search tools, but the price is very high, so you really have to "bite the bullet" (you may be beaten by the other half, which hurts! )。 Mirrors can also be considered. A so-called Dobson reflector can be super-large, but the price is extremely low. Searching for new comets is also a good choice.

* Author's recommendation: Fuji Dragon 25X 150MT-SX, intrauterine BR- 14 1, vexcor EN 20X 125HFT.

G.) The same is true for high-order photography:

I think the goal of this level of astrophotography is not only to get a beautiful photo, but also to get a photo with scientific value-a delicate, correct and informative image. I think this hobby must be photographed with CCD, so as to get scientific information from digital images quickly.

This kind of hobby is actually not very good to recommend binoculars, because it is already a high-level hobby, and the familiarity with equipment is never below me. And the higher the hobby, the more subtle the field you are good at, and the demand for equipment in various fields can be said to be completely opposite! So I won't say much (it seems a bit confusing).

* Author's recommendation: unable to recommend.

H.) Sacrificial-type common interest:

What? Sacrificial type? Just kidding! Why do people pay for binoculars to worship? Hey hey! In my classification, there are! In my opinion, it is a sacrifice to buy a telescope at home and take it out to see it or not to take it twice a year (I am too lazy to use it, not because I have no chance to use it). i*b

As for this type of telescope, I don't think the quality of the telescope needs much consideration, but the spectacular is the key! Because "spectacular can be pleasing to the eye"! If this telescope is the only one in Taiwan Province Province, it is even more worth buying.

* Author's recommendation: MEADE LX-200-40, CELESTRON C- 14. ExIK

I.) Make good use of Zhang Zhongmou style:

It's not that TSMC boss goes to the sea to play astronomy, but that when you have as much money as him, you can consider buying a telescope-well ... it's more appropriate to consider opening a telescope optical factory.

Just kidding! But if your budget has no upper limit, I strongly suggest that you build a small astronomical science museum or observatory, and then have a 40 ~ 60 cm telescope for studying celestial bodies, which is open to the general public.

Why not make it bigger? To build such a large telescope, we should consider not the size or budget of the aperture, but the atmospheric tranquility where the telescope is located. If the tranquility of the atmosphere is not good, then no matter how big the caliber is, it just looks brighter and doesn't help the resolution. There is no need to spend more money. For this kind of hobby, choosing the location of the telescope is more important than choosing the telescope.

* Author's recommendation: Sanying optical device GNF-50. This article is my experience in astronomy for more than ten years, and its purpose is only to provide a reconfirmation before buying a telescope. The binoculars recommended in this paper are all my strong subjective opinions, which do not represent other good opinions, nor are they necessarily the mainstream opinions in the market. Please judge for yourself whether to accept them. I hope I can get a clear picture, but maybe it's just a bright future to some extent.