原文： 2.2.1 Telescope Aperture Considerations Howbig is “big”? In the 1960s everybody’s dream scope was an 8-inch f/8 Newtonianreflector on a machined equatorial mount. In the 1970s the dream telescope hadescalated to 12.5 inches in aperture. By the ‘80s, serious observers all lustedfor a 17.2-inch Dobsonian. As the ‘90s progress, everyone seems to want ahumongous Dobsonian, and the bigger the better. Ten years hence, who knows whatwe’ll want—probably something inthe 1-meter class. But, despite the trend to ward bigger and bigger, monster scopesare not for everyone. It may take some tough soul-searching to decide what sizeis best for you. 译文: 2.2.1望远镜口径的思考 多大才算“大”？60年代，每个人都梦想拥有一台配套赤道仪的8寸f/8牛反。70年代，口径逐渐升级到12.5寸。80年代，发烧友都渴求17.2寸DOB。到了90年代，似乎每个人都想要一套大型DOB，越大越好。谁又能知道十年之后我们想要什么——也许发展到米级吧。尽管口径的趋势是越来越大，但怪兽级望远镜并不适合所有人。这要深思熟虑才能决定什么尺寸才是最适合你的。 Theimportant word here is YOU. Sure, it’s prestigious to own a big telescope, butdon’t give in to perverse telescopic machismo. Aperture envy is a fataldisease. Build a telescope that’s practical for you to use easily on clearnights. Don’t feel guilty or insignificant because you don’t own the biggestscope in your time zone. Any telescope makes poking around the sky a lot morefun. 最重要的词是“你”。当然，拥有一台大望远镜能提高你的逼格，但逼格终究是身外物。攀比口径是一种病，容易染上，但请放心，可防可治。造一台实用的能在晴朗夜空中轻松使用的望远镜，别为望远镜不够大而产生任何消极的想法，任何望远镜都能给你漫游星空时带来更多的乐趣。 Howdo scopes of different aperture stack up? 不同口径的望远镜的比较 Well,an 8-inch is terrifically handy. Short and compact, it can sit unobtrusively onthe porch or in the corner of the garage. Forty pounds to carry; set it up andbe observing in five minutes. It is able to show you all the basic stuff in thesky. A 12-inch is a commitment. From porch to back yard, it takes two trips tocarry the scope and a third trip for the eyepiece box. You need a minivan orstation wagon to carry it. But it’s a lifetime telescope for the seriousobserver, capable of heavy-duty planetary, lunar, and deep-sky observing. Hundredsof easy galaxies. Use it in your back yard or take it on field trips to darkskies. Make no mistake—you could bevery happy with a 12-inch telescope. 8寸镜子是相当便携的，短小精悍，它可以乖巧的待在门廊和车库的角落。四十多斤的重量，五分钟内就能架设好开始观测。它能向你展示天空中所有的基本元素。12寸镜子要麻烦一点，要跑两趟才能把镜子从门廊搬到后院，还要跑第三趟拿目镜箱。你需要一辆小型货车才能搬运它。但它是一台发烧友都能终身受用的镜子，能够高倍观测行星、月亮还有深空目标。轻松能看到几百个星系。在你的后院使用或者带到漆黑的夜空下，毫无疑问，你会很开心的。 Somewherearound 16 inches aperture, you break into a whole new class of observing—thousands of galaxies and globulars resolves to the core are yoursfor the viewing. But you now need a short stepladder. Observing becomesclimbing. Set up in perhaps ten minutes if you’re well organized, and nolugging a small person can’t easily handle. A great scope for half-nighters andall-nighters under nearby rural skier. 16寸的镜子，你会进入一个观星的新境界。数以千计的星系和核心分解的球状星团将映入眼帘。但你现在需要一把短梯。爬梯成为了观星的一部分。乐观估计，架设好镜子需要10分钟，基本上不开挂一个人很难轻松搞掂。总的来说，那是一个能令你通宵的镜子。 Aperturesin the mid-20s open another realm. Gaseous nebulae become more than faintsmudges and smears. Wherever you point your telescope, you see galaxies. Yourfriends tell you that they’ve (gasp!) never seen the Whirlpool Galaxy so wellbefore. On the down side, observing in your back yard is no longer worth theeffort of setting up because the 12-inch will show you just as much, but underdark country set up, but it’s a lot nicer to have a friend or two along toshare the work—and the pleasure—of observing. 20寸大炮轰开了一片新天地。星云不再是一团模糊的棉絮，不论你将望远镜对准哪里都能看到星系，你的朋友会喘着大气告诉你，他们从未如此清晰的看到旋涡星系的悬臂。另一方面，你不能再安逸的在后院观星了，因为不会看到比12寸更多的东西。但在无光害的乡下和三两好友一起架起大炮，一起分享观星的乐趣，那叫一个快活。 At30 to 32 inches, you’re into big-time ladder games. These are the telescopes wecall “The Big Ones”, in part because of the big ladder you need to reach theeyepiece. Before you become fully conscious of the tendency, you’re choosingthe next object near where the telescope is already pointing so you won’t haveto move the ladder again. Long ago you bottomed out even Uranometria 2000.0,and the most acute problem you face in your observing is figuring out what allthose little galaxies are. Do you want to see a double quasar? Sure, go for it!You’ll find it, too. And, although you need observing companions just to comeup with enough new stuff to look at, you still begin winter observing sessionswith a long, deep gaze at the Orion Nebula. The logistics of going to anobserving site have become something just short of awesome, but you feel deeplyrewarded by the views. 30到32寸，欢迎进入漫长的爬梯子游戏时间。它们是我们说的真正的“大家伙”，部分原因是你需要一把大梯子才能够得着目镜。在目标完全跑出视野之前，你要就近选择下一个目标，这样就不用移动梯子了。翻出你很久以前压在箱底的星图2000吧，现在你观星中面临的最迫切的问题是要搞清楚你在看的那些小星系是哪些。你想看一对双类星体吗？当然，出发吧，你会找到它们的。另一方面，虽然你一个小伙伴不断提供新的观测列表，在冬天深入的观测猎户座星云仍会有新的收获。带上这么大的镜子去一趟观星点的筹备工作足以令人望而却步，但你你会得到丰富的回报。 36inches? 40 inches? You’re starting to push Dobsonian technology to its limits. Youfret about mirror flexure, cool down time, and you actually begin to fear tallladders. Observing is ponderous—but the rewardsare rich indeed. Star clusters look like they’re made out of first-magnitudestars. When a faint supernova pops off in some distant galaxy, you lookdirectly at it and estimate its color. Set up and take down are mandatorytwo-person exercises. At home you observe with a 12-inch scope. And when you goobserving, you take the 12-inch for a few quick observing treats on the side. 36寸？40寸？你到达了DOB的极限。你会担心镜子的变形，热平衡时间，看到长梯就两腿发软。观测变得举步维艰，但回报也是满满的。星团看起来像是由第一星等恒星组成的。当一颗暗弱的超新星在遥远的星系爆发是，你可以直接观测到它，还能看出颜色。安装和拆解必须要两个人才能完成。在家里，12寸是主力，在外面，也能打打酱油过过瘾。 Whyshould this be so? If you have a 40-incher, why even think about lookingthrough a 12-inch? Due to the geography of the universe, the laws of physics,and the design of the human eye and brain, the visual thrill you get fromenormous apertures succumbs to the law of diminishing returns. Compared to the0.2-inch aperture of the naked eye, the 2-inch aperture of a pair of 7X50binoculars gives you a tenfold gain in aperture and a 100-fold growth in light—an astronomical jump into the universe. Another tenfold jump inaperture and 100-fold increase in light takes you to a 20-inch telescope, withso many celestial objects visible you won’t see them all in a lifetime ofobserving. A third tenfold jump in size puts you on Palomar Mountain! 为什么会这样呢？如果你有一台40寸，你还会想用12寸吗？由于物理法则、人类大脑和眼睛的构造，你从大口径处得到的视觉刺激遵循收益递减规律。相对于0.2寸的肉眼，2寸口径的7X50双筒给你10倍的口径和100倍集光力，这天文级别的飞跃能引领你进入宇宙。第二个10倍的增长，你需要一台20寸，你将看到很多一生中难得一见的天体。至于第三个10倍的增长，你得去帕洛玛山（搞了很久没想通这句怎么翻译，后来才想到那里的天文台有200寸的望远镜）。
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