望遠鏡相關外文和翻譯

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>　　制作自己的望遠鏡</b></p>&l

30、t;p>　　Allyn J.Thompson</p><p>　　在望遠鏡出現之前的時間里，人們對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)，數不清的恒星和銀河。</p><p>

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

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

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

34、望遠鏡使它再簡單透鏡的基礎上盡可能看的更遠，把放大倍數提升到30甚至更多。這大概是有效范圍內的極限了，否則，在這個尺寸上它的視野將會大大縮小。</p><p>　　伽利略望遠鏡的一般結構如圖2。一般來說，光線由遠處的物體AB發(fā)出，然后折射通過物鏡O，在焦平面形成一個倒像ba，通過調節(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。這個像是垂直放大的；這個放大率的數值是角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，和鏡頭的直徑數值。目前伽利略望遠鏡被用于制作小型雙眼望遠鏡（觀劇用）和小型雙筒望遠鏡，其中觀劇用望遠鏡的穩(wěn)定倍率大概為2-3倍，雙筒望遠鏡的穩(wěn)定倍率為3-6倍。</p><p>　　1611年，Tycho以前的學生，德國的天文學家Jo

36、hannes Kepler（提出使用一個凸透鏡使光線匯聚于一個點的人）對伽利略望遠鏡進行了改進。圖3展示了這個新組合的優(yōu)點。當光線一旦出現就會被立刻會聚；眼睛可以看到更加寬闊的視野。光線反向穿過目鏡，形成一個倒置放大的虛像B’A’。之前說過，放大倍率的數值時角C‘和角C的比例。而這個新發(fā)明的望遠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。這些極長的望遠鏡，工作視野最多只有2-3分度。木星的角直徑幾乎是一個分度弧，所以17世紀的天文學家們耐心試驗瞄準極長的儀器來觀察。</p><p>　　放大率是望遠鏡一個次要的數據；它的主要功能是收集光線。眼睛總是單一的聚集數量有限的

38、光線，因此，物體的亮度決定了它的可見度；所以，肉眼只能解決數量有限的局部。</p><p>　　直徑相同的物鏡出瞳是不會改善視力的，無論給定的放大率數值是多少，除非通過放大物件的細節(jié)來使它更加清晰明顯。一個1英寸的透鏡，假設它是出瞳直徑的3.5倍，聚集13次光線到足夠明亮時，能讓相應昏暗的物體可見。詳細的數值也會因為孔徑的增加而增加。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的方法就是延長焦距，但是有手持長度這個實際限制。并且，更大的視野只是一個理論理想，而且大視野只有在較短的焦距時才會實現。而要消除色差需要使用連個相同折射率、同種玻璃的鏡頭，只有仍保持有一定數值的色差。</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了---如果所有光學媒體的折射和色散是相同的---

40、-Sir Jsaac Newton試圖克服色差。盡管他的試驗是非常不確定的，但牛頓通過試驗發(fā)現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折射望遠鏡。他因此提出構成完全無色的凹反射面。</p><p>　　反射鏡的實際試驗早在1639年就開始了，但是知道1663年都沒有任何突破。那年一個24歲的蘇格蘭數學家James Gregory,發(fā)表了他的論文題為Optica Promota.在論文中他描述了一