望遠(yuǎn)鏡相關(guān)外文和翻譯

1、<p>　　MAKING YOUR OWN TELESCOPE</p><p>　　Allyn J.Thompson</p><p>　　Por to the timeof the telescope,man’s view of the celestial universe was woefully restricted when compared with what now c

2、an be enjoyed on any clear evening with ordinary binoculars.There were visible to him then only the naked-eye objects,the sun and the moon,five of rhe planets,and on a clear night stars down to about the 6th magnitude, s

3、ome 2000 in all. A few hazy spots could also be seen,and there would be an occasional comet.Completely unknown were the outer planets,satellites of the planet</p><p>　　Yet,working without optical aid,early o

4、bservers managed to make some amazingly accurate charts of the visible stars,and amassed the observations from which the laws of planetary motion were deduced.The principal instrument used in establishing star and planet

5、 positions was the quadrant,a device having a graduated arc,and a pointer that pivoted about its center.With it Tycho Brahe,Danish astrinimer,and one of the keenest of all observers,was able to record the positions of st

6、ar to within one minu</p><p>　　Then,in 1608,seven years after Tycho’s death,the telescope was brought upon the scene by a Dutch spectacle maker,Jan Lippershry,to whom its invention is credited.Theinvention m

7、arked one of the great progressive triumphs of man,enabling him to reach farther and eer farther out into space.It was not much of a telescope,this first refractor,consisting of two spectacle lenses perhaps an inch in di

8、ameter,one convex and the other concave,and magnifying possibly two or three times.Lippershey,whose name</p><p>　　The Galilean Telescpoe.Very soon,spectacle makers and scientists up and down Europe,learning

9、of lippershey’s invention,were making similar instruments.Notable among the scientists was Gakukei Galilei,the great Italian physicist and astronomer,who fitted a plano-convex and a plano-concave spectacle lens into oppo

10、site ends of a lead tube,making a telescope that magnified three times.”They appeared three times nearer and nine times larger in surface than to the naked eye,”wrote Galileo.He experimen</p><p>　　The genera

11、l arrangement of Galileo’s telescope is shown inFIg.2.Ordinarily,rays from a distant object AB would,after refraction through the objective lens O,meet to form an inverted image ba in the focal plane,but by interposing t

12、he concave eye lens E in front of that plane the rays are caused to become divergent,as though they had proceeded from the points A’B’,where a virtual image of the object is formed.This image is erect and magnified;the a

13、mount of magnification is the ratio of angle c’ to</p><p>　　As the eye pupil can hardly embrace all of the rays emerging from lens E,only part of the actual field shown can be utilized.Also.the exit pupil is

14、 located inside the instrument.Tfield of view thus depends on the size of the eye oupil,and on the diameter of the objective lens.The Galilean telescope is found today in the form of opera and field glasses,but employing

15、 quite moderate magnification:2 to 3 power in the opera glass,and 3 to 6 power in the field glass.</p><p>　　The Keplerian Telescope.An improvement on Galileo’s telescope was made in 1611 by Johannes Kepler,a

16、 German astronomer and former pupil of Tycho,who suggested that the converging rays from the objective be allowed to come th a focus,and that the resultant image be magnified with a convex lens.Fig.3 shows the advantage

17、of this new arrangement.T rats,upon emergence from the eye lens,are now converging;hence more of them and a wider field of view can be taken in by the eye.Projected backward through</p><p>　　But with increas

18、ing magnification,the inherent defects of a lens,notably chromatic and spherical aberration were likewise increased.The aberrations could be diminished to a considerable extent by lengthening the focus of the objective l

19、ens. Consequently,in efforts to reduce these aberrations,enormous proportions were reached,instruments of 130 and 150 feet in length being constructed.Lens diameters up to six inches and more were attained.Non-spherical

20、surfaces were also attempted in an endeavor </p><p>　　Magnification is a secondary condary consideration of the telescope;its chief function is to collect light,The eye alone gathers a limited amount of ligh

21、t,hence the lununosity of an object determines its visibility;also,the unaided eye can resolve only a limited amount of detail.An objective lens of the same diameter as the pupil of the eye would not improve vision,regar

22、dless of the amount of magnification employed,except that thtough this enlargement the detail in an object would be made more a</p><p>　　But since spherical aberration increases with the square of the apertu

23、re,the only way in which it could be kept under control was to lengthen the focus,but there was a practial limit to what lengths could be handled.Moreover,a larger field of view was greatly desired and this could accrue

24、only with the use of shorter focal lengths.While spherical aberration could be pretty well eliminated by the use of two suitably curved lenses of the same kind of glass,there still remained chromatic aberration</p>

25、<p>　　In the hope of combining lense of different glasses in such a way as to overcome chromatic aberration,Sir Isaac Newton attempted to determine if refraction and dispersion were the same in all optical media.A

26、lthough his experiment was inconclusive,from it New ton assumed that refraction and dispersion were proportional to each other,and he decided that nothing could be done to improve the refractor.He therefore directed his

27、energies to the formation of images from concave reflecting surfaces,whic</p><p>　　Practical experments with reflectors had already begun in 1639,but it was not until 1663 that they gained any prominence.In

28、that year a Scottish mathematician,James Gregory,at the age of 24,published a treatise entitled Optica Promota.In this he gave a description of a compound reflecting telescope employing two concave specula.The larger one

29、 was to be perforated,and to have a paraboloidal surface; the smaller was to be ellipsoidal. The arrangement is shown in Fig.6.Notice that the ellipsoidal m</p><p><b>　　制作自己的望遠(yuǎn)鏡</b></p>&l

30、t;p>　　Allyn J.Thompson</p><p>　　在望遠(yuǎn)鏡出現(xiàn)之前的時(shí)間里，人們對(duì)于宇宙和天空的視野只能悲哀的被限制在用普通的肉眼可以看清天空的夜晚里。只有那些裸眼可見的物體，太陽，月亮，五大行星和清晰夜晚大約2000顆亮度巨大的恒星。一些模糊不清天體的也是能看見的，包括一些偶然的彗星。不被人們知道的外太空行星，行星的衛(wèi)星，土星環(huán)，數(shù)不清的恒星和銀河。</p><p>

31、;　　在沒有光學(xué)儀器的幫助下，早期的政府觀察員制作了出乎意料的準(zhǔn)確的可見恒星分布圖，并積累推演出了行星奉行的運(yùn)行規(guī)則。這些儀器原理應(yīng)用在已經(jīng)確定的恒星和行星位置象限儀上，這個(gè)儀器有一個(gè)刻度弧，和一個(gè)中心指針。丹麥天文學(xué)家Tycho Brahe和一個(gè)熱心的觀察員準(zhǔn)確的記錄了一個(gè)分度內(nèi)的恒星位置---大概是月球直徑的1/30。這是一項(xiàng)令人驚訝的業(yè)績，當(dāng)它考慮到一分度大概是一個(gè)尖銳視角的極限。</p><p>　　到了

32、1608年，就是Tycho死后的第七年，望遠(yuǎn)鏡被一個(gè)荷蘭眼鏡制造者，Jan Lippershey制作出來,因?yàn)榘l(fā)明望遠(yuǎn)鏡而被世人銘記。這個(gè)發(fā)明是人類史上一個(gè)巨大而先進(jìn)的勝利，使人們可以探索和發(fā)現(xiàn)更加遙遠(yuǎn)的外太空。它甚至算不上一個(gè)完整的望遠(yuǎn)鏡，人類歷史上第一臺(tái)折射望遠(yuǎn)鏡，只是由兩塊透鏡組成的一英寸直徑大小的儀器，由一個(gè)凸透鏡和一個(gè)凹透鏡，放大率只有大概2-3倍。Lippershey，這個(gè)被許多歷史學(xué)家用不同方式記住的人，使兩種器械結(jié)合在一

33、套裝置中，從而發(fā)明了第一臺(tái)雙目望遠(yuǎn)鏡。</p><p>　　很快，歐洲上上下下的眼鏡商和科學(xué)家們學(xué)習(xí)研究了Lippershey的發(fā)明之后，制作了更簡單的儀器。這些科學(xué)家之中值得注意的是Galileo Galilei,，意大利偉大的物理學(xué)家和天文學(xué)家---那個(gè)組裝了由一個(gè)凸透鏡和凹透鏡安裝在直管兩頭，制作了一個(gè)放大率為3倍的望遠(yuǎn)鏡的人?！八鼈?cè)谄矫嫔峡雌饋肀嚷阊劭吹綍r(shí)近了3倍，大了9倍”，伽利略寫道。他嘗試改進(jìn)這個(gè)

34、望遠(yuǎn)鏡使它再簡單透鏡的基礎(chǔ)上盡可能看的更遠(yuǎn)，把放大倍數(shù)提升到30甚至更多。這大概是有效范圍內(nèi)的極限了，否則，在這個(gè)尺寸上它的視野將會(huì)大大縮小。</p><p>　　伽利略望遠(yuǎn)鏡的一般結(jié)構(gòu)如圖2。一般來說，光線由遠(yuǎn)處的物體AB發(fā)出，然后折射通過物鏡O，在焦平面形成一個(gè)倒像ba，通過調(diào)節(jié)焦平面前的凹透鏡E使光線發(fā)散，好像是由虛像A’B’發(fā)出形成的。這個(gè)像是垂直放大的；這個(gè)放大率的數(shù)值是角C’和角C的比例。</p

35、><p>　　由于眼睛的瞳孔很難抓住所有由透鏡E折射的光線，實(shí)際證明只有很少一部分可以被利用。所以，出瞳是位于儀器內(nèi)的。如此一來視野的范圍就取決于瞳孔的尺寸大小，和鏡頭的直徑數(shù)值。目前伽利略望遠(yuǎn)鏡被用于制作小型雙眼望遠(yuǎn)鏡（觀劇用）和小型雙筒望遠(yuǎn)鏡，其中觀劇用望遠(yuǎn)鏡的穩(wěn)定倍率大概為2-3倍，雙筒望遠(yuǎn)鏡的穩(wěn)定倍率為3-6倍。</p><p>　　1611年，Tycho以前的學(xué)生，德國的天文學(xué)家Jo

36、hannes Kepler（提出使用一個(gè)凸透鏡使光線匯聚于一個(gè)點(diǎn)的人）對(duì)伽利略望遠(yuǎn)鏡進(jìn)行了改進(jìn)。圖3展示了這個(gè)新組合的優(yōu)點(diǎn)。當(dāng)光線一旦出現(xiàn)就會(huì)被立刻會(huì)聚；眼睛可以看到更加寬闊的視野。光線反向穿過目鏡，形成一個(gè)倒置放大的虛像B’A’。之前說過，放大倍率的數(shù)值時(shí)角C‘和角C的比例。而這個(gè)新發(fā)明的望遠(yuǎn)鏡可以極大的提高放大倍率。</p><p>　　但是隨著放大率的增加，鏡頭的固有缺陷，尤其是色差和球面像差也同樣增加。延

37、長物鏡的焦點(diǎn)可以很大程度上的減少像差。因此，這些像差是可以通過努力而大比例的減少，長度為130-150英尺的儀器正在制造。透鏡的直徑達(dá)到六英寸甚至更多。非球形表面也努力試圖克服球差。這些極長的望遠(yuǎn)鏡，工作視野最多只有2-3分度。木星的角直徑幾乎是一個(gè)分度弧，所以17世紀(jì)的天文學(xué)家們耐心試驗(yàn)瞄準(zhǔn)極長的儀器來觀察。</p><p>　　放大率是望遠(yuǎn)鏡一個(gè)次要的數(shù)據(jù)；它的主要功能是收集光線。眼睛總是單一的聚集數(shù)量有限的

38、光線，因此，物體的亮度決定了它的可見度；所以，肉眼只能解決數(shù)量有限的局部。</p><p>　　直徑相同的物鏡出瞳是不會(huì)改善視力的，無論給定的放大率數(shù)值是多少，除非通過放大物件的細(xì)節(jié)來使它更加清晰明顯。一個(gè)1英寸的透鏡，假設(shè)它是出瞳直徑的3.5倍，聚集13次光線到足夠明亮?xí)r，能讓相應(yīng)昏暗的物體可見。詳細(xì)的數(shù)值也會(huì)因?yàn)榭讖降脑黾佣黾?。所以很明顯早期的觀察員需要較大的儀器來獲得更大的聚光和分辨率。</p>

39、;<p>　　但是由于球差隨著廣場孔徑的增加，唯一可以讓它保持在可控制范圍之內(nèi)的方法就是延長焦距，但是有手持長度這個(gè)實(shí)際限制。并且，更大的視野只是一個(gè)理論理想，而且大視野只有在較短的焦距時(shí)才會(huì)實(shí)現(xiàn)。而要消除色差需要使用連個(gè)相同折射率、同種玻璃的鏡頭，只有仍保持有一定數(shù)值的色差。</p><p>　　懷著克服色差的希望，使用兩種不同的棱鏡組合的方式出現(xiàn)了---如果所有光學(xué)媒體的折射和色散是相同的---

40、-Sir Jsaac Newton試圖克服色差。盡管他的試驗(yàn)是非常不確定的，但牛頓通過試驗(yàn)發(fā)現(xiàn)折射和色散和相互成比例的，他還定義沒有任何東西可以提高改進(jìn)折射望遠(yuǎn)鏡。他因此提出構(gòu)成完全無色的凹反射面。</p><p>　　反射鏡的實(shí)際試驗(yàn)早在1639年就開始了，但是知道1663年都沒有任何突破。那年一個(gè)24歲的蘇格蘭數(shù)學(xué)家James Gregory,發(fā)表了他的論文題為Optica Promota.在論文中他描述了一