城市观星指南（英文原文）
; R1 Z1 ^- ^8 u. N$ n著：Alan M. MacRobert 译：Shea天文家园欢迎您！. \# y8 _7 x5 r8 ]
对于业余天文学家来说，现在是最佳的年代，同时也是最糟的。从来没有过如此大而精良的望远镜，同时各式各样的附件你也可以随处买到。从来没有过如此多的天文信息，你只要轻点鼠标就可以一览无疑。但是，也从来没有过如此多的人生活在如此糟糕的星空之下。许多《天空和望远镜》的读者可以在计算机屏幕上跟踪公元前3000年冥王星的运动轨迹，但却无法在户外的光污染中找到北极星。国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材$ O8 ?- o" d  `3 ^
随着装备的改善以及黑暗天空的消失，这一矛盾黑变得越来越尖锐。也许，业余天文学的未来即是全世界未来的缩影——高度发达的技术和受到污染的环境。
$ C2 l# V2 y6 h2 y. n3 @" S国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材这两者哪个会跑得更快，并最终占据主要地位，每个人都在猜测。然而，有一点是明确的。环境是大家的——但是设备的所有权是个人的。星空是属于每个人的，但是欣赏星空的权利正在逐渐私有化。许多曾经很普遍的天文现象现在已需要昂贵的设备、大量的金钱和时间，到远离城市的郊外才能一睹她的芳容。天文家园欢迎您！  a  h! @4 ]7 h6 a2 s
然而，无论未来会变成什么样子，一些观星者不会让任何东西阻止他们。他们是这样一群人：他们在城市里架起望远镜，观测时用毯子盖住自己的头，以此来遮挡附近的灯光；他们花费一年的时间来检测由公寓的窗户得到的模糊星像，并且由此绘制出变星的光变曲线；他们通过记录恒星被摩天大楼掩食的时刻，来确定地轴岁差的比率。天文望远镜器材评测和交流论坛, |% U9 M2 \' P) U  i6 g
“普通”的观测者，他们拥有令人满意的壮丽星空，倾向于把这些天文爱好者视为业余天文学界的怪物。可是他们错了。随着世界人口越来越稠密、城市化以及越来越多的照明设备，这些城市观星者正是探索我们未来之路的先锋。www.astroview.com.cn+ B  p4 u" ?  F$ [3 I1 T6 {- W5 a
有窗户的房间……www.astroview.com.cn7 [, e5 Q, @4 s$ }7 M5 b
数年前，在我搬入康尼迪克州的新港（New Haven, Connecticut）闹市区之后，我出乎意料地发现了城市观星的可行性。我曾认为天文观测会从我生命中消失。但是，有一晚仅仅是为了好玩，我用7×50的双筒望远镜，从我公寓阁楼的天窗向外望去。令人惊讶地是，我竟然能辨认出一些恒星。
6 c" F) ~6 T$ h在这种情况下还能观测到一些东西，实在让人感到惊讶，为此我做了一些试验。使用《天空和望远镜》提供的刍藁增二（鲸鱼ο）的星图，我发现我双筒镜的极限星等可暗至8.6等。我曾经观测到在最低亮度附近的刍藁增二。天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪$ a: R2 [+ j% L) D. ]" ~
星像会由于天窗的塑料护板而扭曲，这是事实，但它们确实在那儿。当然，大多数的恒星在此极限星等之上！在接下去的几个月里，我更加仔细的用双筒镜观测星空。我挑选一小块天区，观察研究其中的每一个天体——恒星的距离、光谱类型，以及一些有趣的天体——并且绘制一张小星图。我在天窗旁放了一块手写板，并且把那里布置得很舒适。它是我的小天地。在那儿，我跟踪麒麟座T 每个月的脉动，金牛座Y 不可预言的亮度变化，以及小行星的缓慢移动。在平时，我观测一些双筒镜力所能及的双星，同时我会花很长时间来绘制在猎户座腰刀区所能见到的一切东西，而且我还能辨识出月球上的辐射纹。
& s. O3 t" F! T1 B- }) l4 q天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪意料之外的回报开始出现。你观测条件的限制会使你得到磨练；当然也不要毫无目的地观测，我每次都查阅星图和星表，预先制定出一个计划。这是你得到回报的关键。当我将双筒镜压在天窗的护板上时，天窗的内壁为双筒镜提供了一个坚硬的挡板。美丽而稳定的星像补偿了塑料造成的光学畸变以及外面笼罩的一层灰色薄雾所带来的干扰。当几英寸之外还是寒风凛冽时，而我却穿着衬衫在观察猎户座，这真是一种奇妙的经历。天文望远镜器材评测和交流论坛5 i: H; b2 c5 d* d
教训是明显的。前期准备、稳定的星像以及舒适的观测环境将有助于在恶劣的环境中进行天文观测。& ?' T* _/ `; s
如果这些都能做到，望远镜就可以提供更多的机会。月亮和行星会展现出更多的细节，就像在乡村能见到的一样。事实上，城市中充满着热源，它们会引发大气湍流，使观测条件变差。但是，城市中的薄雾可以提供一个稳定的大气条件。
' M# u: D! m+ k* }南卡罗莱纳州查尔斯顿（Charleston, South Carolina）的吉姆·菲利普斯（Jim Phillips）是许多城市观星者中的一员。菲利普斯把他的观测时间都献给了月亮和行星。“坦率地讲，”他写道，“由于住在市中心地区，我对有多少可观测的夜晚表示怀疑。”在他的车库天文台中，他使用一台定做的8英寸f1/3的折射望远镜。“我很久以前就意识到，我可能会永远住在城里或是城市周围，而且在一番思考之后，我决定不要一台便携式望远镜，尽管我可以把它带到郊外，我宁可要一个在有光污染的地区的天文台。对我来说，在天文台使用星图、书籍和星表所带来的便利，以及在几分钟之内就可以开始观测的便捷性，远超出了光污染和建筑物的阻挡所带来的弊端。”
) N5 P* C" Q7 O# [+ x* a国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材“我可以分解出靠近望远镜理论极限的双星。同时，木星的细节总是让人着迷，就像月亮表面的细节。”菲利普斯最终接手了月亮和行星观测者协会的月丘观测计划。
2 K6 q) K& t: G: T4 Fwww.astroview.com.cn其实，并不需要用这么大的望远镜来解决观测上的问题。密歇根州的罗伯特·班什（Robert W. Bethune）使用3.5英寸的望远镜近两年，在韩国汉城从事观测。汉城像世界上许多大城市一样充满着烟雾和光污染。“我的住处被街灯照的通亮，”但是，他写道，“月亮总是最有趣的天体。今年夏天提供了一个研究木星、土星系统的绝佳机会。通过练习和实践，在光污染中仍有许多变星、双星，甚至行星状星云可以观测。我最大的成功是记录到昴星团中一颗8等星被掩食。”
! d* \# T# V, Z0 S0 [班什提供了一些秘诀，“每个人对灯光都有自己的看法。我对付那些讨厌的灯光的办法是在观测时把路灯的灯泡拧开，当然在观测完之后要把它们装回去。”国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材7 [- c3 K- Z! V' `$ @! Q
“晚睡早起是有帮助的。就算是最大的城市，午夜之后任何东西也都会松弛下来。周详的计划也很有好处。在星表或星图中找出在你所能见到的天区将会发生的天象，会提高你的技艺。最重要的是接受环境对你的限制，在仔细的试验和研究之后，了解并想法减弱它们对你的影响。”! }+ ^* @, C) H, z
对于任何在业余天文学界野心勃勃地的人来说，将望远镜探出窗外观测是一大忌。室内外的温度差会摧毁稳定的星像。这在有些时候完全正确——但正如迈克尔·布斯恰特（Michael Boschat）所发现的，它不总是正确。“对于行星观测，我把我的3英寸望远镜探出窗外，大部分时候的星像都很稳定，我即使使用200倍的目镜也没有关系。去年夏天，我用这一方法观测火星，甚至当火星在低空时我也能看到其表面上的斑纹。”2 @+ ?$ a. V% G7 j: c9 J+ [  J
请注意，天上总是有太阳的。新泽西的索·斯丁堡（Sol Steinberg）已经退休，住在一套带院子的公寓里。“我的窗户朝向东面，同时我的院子又被8幢房子环绕。”使用一台3英寸的折射望远镜，他拍摄月亮，跟踪木星的卫星和金星的盈亏。“太阳是我每天早晨固定的目标，”他写道，“55mm的目镜可以投影一个明亮的像到我卧室的天花板上，但是这无法和使用滤镜直接观测划等号。”他开始跟踪太阳黑子。“昨天出现了一新的黑子群，而且今晨有两个黑子达到了2弧分——这是一副令人激动的景象。”天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪" E' @3 f$ {5 E
……深空天体
# ?: ]; G/ B7 w6 J星云和星系，有着较低的表面亮度，因此受光污染影响最严重。因此，许多城市观星者在真正尝试之前就放弃了它们。纽约的杰妮·沃斯诺普（Jenny Worsnopp）是那些拒绝认输的人之一。“曼哈顿对业余天文学家来说是最糟糕的居住地。”她写道，“我最钟爱深空天体，该怎么办呢？”答案是走出去，用心去寻找。国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材9 {$ w/ z! ?. J$ s3 n+ |7 X& y
在她公寓的房顶上，沃斯诺普有一片开阔的天空，但却被照的通亮，就象是帝国大厦。但是，沃斯诺普用她的6英寸望远镜观测到110个梅西耶天体中的46个。“疏散星团和明亮的球状星团甚至在午夜前就能被观测到，”她说。在午夜之后，许多建筑物会关掉装饰灯，“在这之后，天空就是我们的了。”www.astroview.com.cn( E" E% A" P' I6 k$ X/ j, h
“最近我得到一个惊喜。我晚上12:30来到屋顶，观测到了M104、M66和M81，让人惊讶的是还有M97，”一个大而暗的行星状星云，在任何环境下都是很难看到的。“我使用一块OⅢ星云滤镜和视场移动法找到了它。”
! E: z; m. F3 h$ B8 i4 _这些技艺需要实践和技巧。“城市观星，”沃斯诺普说道，“对于那些醒目的天体是一种很好的训练 ；城市观星者无法通过寻星镜找到梅西耶天体，并且将它们调至视场的中央；我们不得不找到它们的精确位置，因此我们都必须十分熟悉星图。我敢说，如果我能在这儿看到它，那你无论在什么地方都能看到它。”0 l- g9 |9 ^5 g! H
沃斯诺普的纪录被伦敦的大卫·弗莱德曼（David H. Frydman）打破。“我已经在城市里观测天体30年了，”他写道，“使用一台5英寸的折射镜，我已观测了我所知的500个深空天体中的350个，其中大多数都不只一次。”他提供了许多建议：
7 M0 D/ V3 Z4 g) h6 ^9 w( S  ^天文望远镜器材评测和交流论坛“找一扇半径25°的窗户，在天顶方向即使有光污染也能看到暗弱的天体，任何尝试都不应该中途放弃。”天文望远镜器材评测和交流论坛% A  ]$ G2 t) ?' A- C
“尽量排除当地光污染对你的干扰。观测最好在晚上11点之后进行，选择受保护最好的地方，而且，如果必要，可以在你头上或望远镜上照上一个开口的盒子。”" S/ d' a; {" |" t2 m% I
“雨后或是刮大风时是最佳机会。在大风中我看到了帷幕星云（NGC 6992），夜枭星云（M97）包括其中的‘黑眼’，以及M33中更多的细节。通常前面两个在5英寸折射望远镜中是看不见的。”
5 a8 w" M4 M' [3 U4 @弗莱德曼强调，非常详细的星图是必需的。“如果你知道一个天体的确切位置，那你可以多看1个甚至2个星等。等一会儿，它们会慢慢的从视场中浮现出来。”
" m, o; ^  k1 G5 O5 u. L3 {国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材一个深空天体是否在光污染中可见，取决于它的表面亮度而不是它的总亮度。因此，当你搜索星表寻找目标时，应该选那些亮而小的目标。
9 q/ Q4 D3 E3 q天文望远镜器材评测和交流论坛许多小的行星状星云有较高的表面亮度。在1986年夏天出版的《深空天体杂志》上阿里斯特·林（Alister Ling）公布了一张60个的“城市中可见的行星状星云”表。其中许多看上去呈恒星状，而且必须用高倍目镜才能解析出来——没有详细的星图更本无法识别出它们。林提供了一些秘诀来区别它们。其中一个使糟糕的观测环境有了用武之地：行星状星云比起恒星来很少闪烁，同样的，行星也很少闪烁（它们都有一个可见的视面）。另一个诀窍是，它们不像恒星那样呈现出蓝色或绿色。天文望远镜器材评测和交流论坛) L/ t" j/ f1 o1 e
在林的星表中，最佳的“城市行星状星云”是大于15弧分、亮于10等的，鲜为人知的：位于波江座的NGC 1535，长蛇座的NGC 3242和天鹅座的NGC 6826。显然，这是一片广阔的领域等待探索。天文望远镜器材评测和交流论坛& Q, {0 N& Q1 q0 j/ T
另一篇最近出版的有关高表面亮度行星状星云的文章是唐纳德·弗格森（Donald R. Ferguson）在1995年4月份出版的《天空和望远镜》上发表的那篇文章。弗格森列出了一张含有18个行星状星云的星表，这些都是他通过3.5英寸望远镜在休斯敦市中心所能看到的行星状星云。: x! k9 Y% H7 [. A( L/ W' u
星云滤镜
  T0 p: r& C( \( t! p( j# g当70年代末星云滤镜被开发出来时，城市和郊区的观星者又有了通向深空天体的利器。星云滤镜的工作原理很简单。发射星云发出的光在一个很窄的波段上，与钠或汞蒸汽的路灯发出的光既然不同。通过一个多层干涉滤镜，可见光谱可以被分割得足够细，分离出这些特定的光。结果是暗得多的天空，不同程度变暗的恒星和星系，和仅仅变暗一点点的行星状星云和发射星云。在大多数情况下，这一加强的对比度可以弥补星云相对小的亮度损失，并且使之显得更清晰。天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪7 Y9 L7 T/ e4 Q5 ~% l: I
这些滤镜不会把乡间的星空带回城市，但它们确实有帮助。有一种用于探测星云，尤其是小型行星状星云的技术，被称之为滤镜“闪烁”。当滤镜快速地移出视场，你会发现星云会相对周围的恒星闪烁。同样地，你也可以通过来回地倾斜滤镜来做到这一点，因为滤镜一旦倾斜就失去了功效。天文望远镜器材评测和交流论坛3 O: W/ s  Z0 }; w  K4 l
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[ 本帖最后由 siqingtan 于 2008-4-20 10:12 编辑 ]

许多星云滤镜已经可以买到。它们对于不同的天体、不同的环境，使用不同的对策。
, I; J0 @! z$ r! P- w天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪CCD照相机天文望远镜器材评测和交流论坛- T6 X/ e$ k! U1 I
对于那些既可以承受它的价格又可以为之花时间的人来说，最有希望的新技术莫过于CCD照相机了。CCD照相机已经把业余天文学拓展到了前所未有的高度，而且它们的价格每年都在下降。CCD有两大优势。其一，比起肉眼和底片，CCD对光更加敏感上数倍。其二，它可以将望远镜接受的星像直接数字化存入计算机，在那儿图像可以得到改进、分析、测量和处理。
) `1 ~$ ?: l0 z( ~/ a: g% F天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪最重要的处理是可以从图像中去除光污染的影响，就象是变魔术，几乎不会造成数据的丢失。一台8英寸的望远镜在城市的灯光或月光中可以拍摄到15等甚至16等的恒星。这比用同样的望远镜在山区黑暗的情况下肉眼所能见的极限还要暗数倍。
$ ]7 W' P5 a; K1 c% {" o& S) h天文家园欢迎您！CCD的缺点是它的视场非常小，很难定位和调焦。而且CCD经常变化无常，望远镜的支架必需足够坚固，并且对于长时间曝光要易于操控。当然，你是看着计算机屏幕，而不是星空。CCD天文学是望远镜和计算机的工作，而不再需要凝视星空。
; ~9 j- `0 T. n4 W0 ~' gCCD的最大优点是：记录的数据可以进行科学处理。在19世纪，在使用技术方面业余天文学家和专业天文学家几乎是平起平坐。之后，天文爱好者就被渐渐的甩在了后面——而现在CCD正在收复这些失地。业余天文学家正在大批量的发现小行星，从事专业级的变星研究，探测19等的γ射线爆的光学对应体，拍摄恒星和星系的光谱，拍摄越来越精细的行星照片，等等。
8 R" [0 N! M% P- |! ]+ r6 _www.astroview.com.cn然而，没有机器可以取代简单而令人愉快的肉眼观星活动，因为这是自然生活的一部分。
0 z0 v+ U/ F/ U1 Q" _/ j  @- o天文家园欢迎您！逃避还是面对天文望远镜器材评测和交流论坛5 j) j! `* q; {, q9 [
“光污染是天空中的光亮。它不应与直接射入观测者眼睛的光相混淆。”
& G) A# D( }  K. b5 O" }天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪当地的灯光使观测条件恶化，但是却很容易对付。许多观测者都有着合作的邻居，他们会应你的要求关掉户外的灯光。另一个打破僵局的方法是让邻居也来分享观星所带来的乐趣。
' ]3 u( u/ v3 C1 V# t国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材如果你无法在树或墙的影子下观测，你可以用防水布搭建一个观测场。马克斯·韦斯伯（Max Wyssbrod）住在瑞士，他称其为“欧洲最亮的国家”。他的“布制”天文台含有4根10英尺场的铝柱，它们插入水泥中，大约占地10平方英尺。西面的墙是用黑布做的，绳索用于增加整个建筑的稳定性。整个天文台有一台8英寸的施密特—卡萨格林望远镜，只需15分钟就可搭建完毕。
$ D! _  t9 ?2 @/ x- |+ g0 c天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪另一种对策是，仅保护你的眼睛，以及望远镜的前后两端。一件老式的照相用黑色工作服，或者是一顶帽子，就可以取得很好的效果。任何在明亮灯光区的望远镜都需要一个较长的镜罩，以防止杂光进入镜筒。目镜也应该有橡皮眼罩。
& g, W0 {7 M8 m% y* y国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材“我用一块黑色的头巾，和用扑克牌做的眼罩，”田纳西的查尔斯·汉（Charles Haun）写道，“它们很管用。”& Z; T  f6 E2 w( M/ [" |9 D
躲在黑布后面或是带着眼罩来感受宇宙的辉煌可能不大体面。但是，这样的装束可以使业余天文学家更有信心的面对未来。

译自 《Sky and Telescope》
: [: {5 \9 r( O9 ^! b0 x$ g& S3 j$ o Observing from the City
# x8 z1 Y" j% kwww.astroview.com.cnBy Alan M. MacRobert天文望远镜器材评测和交流论坛9 D9 ~9 b0 m% Z: d2 ^* U; n
www.astroview.com.cn/ z2 B8 P+ Z9 W/ u6 e! G3 B
For amateur astronomers these are the best of times and the worst of times. Never have such large and sophisticated telescopes and such powerful accessories been so readily available at moderate prices. Never has so much celestial information been available at the flip of a page or click of a mouse. But never have so many people lived under such awful skies. Many Sky & Telescope readers can follow the motion of Pluto in 3000 A.D. on a screen, but cannot step outdoors and find Polaris through the light pollution.
4 L' H) Z0 v- p& `天文家园欢迎您！This paradox will grow ever more extreme as equipment improves and dark skies retreat. The future of amateur astronomy is, perhaps, a microcosm of the rest of the world's future: better technology in a poorer environment. 天文望远镜器材评测和交流论坛/ ~: i) }: \3 p
Which of these two trends will outrun the other and become dominant is anyone's guess, in amateur astronomy as in the larger world. One result, however, is already becoming clear. The environment is public -- but equipment ownership is private. The stars belong to everyone, but access to them is becoming privatized. Many once-common celestial sights already require expensive instruments or the money and time to travel to distant, unspoiled locations. $ U  S" k6 M% L8 C4 ]
No matter what the future holds, however, some observers will never let anything stop them.
3 E  }+ `; {  f4 A  w6 ?+ Z1 n: U, e1 q天文家园欢迎您！These are people who set up telescopes in city lots and observe with blankets draped over their heads to block streetlights, while keeping an ear out for muggers. These are people who spend a year examining bleary star images through an apartment window and come away with a sheaf of variable-star light curves. These are people who time the instants when stars are occulted by skyscraper walls and determine the rate of precession of the Earth's axis. 国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材! g+ V  i( d' u% g" p+ U, k
"Normal" observers who have (or travel to) decent skies tend to regard such enthusiasts as crankish inhabitants of an unimportant amateur-astronomy backwater. They are wrong. As the world grows more densely populated, urbanized, and brightly lit, city observers are the vanguard exploring trails to our future.
/ F2 Z7 P0 ?) z; @% d5 H. h2 b天文望远镜器材评测和交流论坛Rooms With A View...
( d0 U/ ~- G8 h8 ~国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材Years ago I discovered the unexpected possibilities of city observing after moving into downtown New Haven, Connecticut. I assumed that skywatching would cease to be part of my life. But our garret apartment had a plastic bubble skylight over the kitchen sink, and one night, just for laughs, I tried looking through it with 7×50 binoculars. Amazingly, I could make out some stars. 天文望远镜器材评测和交流论坛; Z7 h( ^/ w4 [5 \' ~( R
Observing anything under these conditions seemed so remarkable that I did some experimenting. I arranged a way to stand on a stool with my head in the bubble surrounded by light shields. Using a variable-star chart for Mira published in Sky & Telescope, I discovered that my limiting magnitude with the binoculars was as faint as magnitude 8.6. I even spotted Mira near its minimum light.
" m$ d* g# l7 ?/ Z8 W- \天文家园欢迎您！Star images were distorted by the plastic bubble, it was true, but they were there. Surely lots could be done with a limiting magnitude this faint! In the following months I explored the binocular sky more carefully than I ever had before. I would pick a small area of sky and research everything about it -- the distances and spectral types of stars, interesting objects to try for -- and draw little maps. I set up a writing board in the bubble and arranged to rest comfortably there. It was my own little world, with my feet on the stool and my head in the stars. I followed the monthly pulsations of T Monocerotis, the unpredictable quiverings of Y Tauri, and the nightly creep of asteroids. Binocular double stars could be surveyed at leisure, and I spent long periods mapping everything I could see in Orion's Sword. I identified scores of features on the Moon.
, g. x3 h: \% E& J( N1 D1 e: f天文家园欢迎您！Unexpected benefits began to appear. Restrictions on your observing impose discipline; rather than aimless sightseeing, I had to do desk work with maps and catalogs beforehand to develop good projects. This turned out to be the key to rewarding astronomy. The inside surface of the bubble proved to be a rock-solid "mount" for the binoculars when they were pressed against it face-on. The beautifully steady views made up for the plastic's poor optical quality and the gray film of pollution coating its outside. And it was a new experience to be in shirt-sleeve warmth examining Orion, while an icy winter wind screamed by inches away.
& x, P" j6 A+ @/ x天文望远镜器材评测和交流论坛The lesson was clear. Desk work, steady optics, and comfort make for fine sky-watching in the worst environment.
" K2 t& P+ J0 D9 d( l# o6 P6 ~* H天文家园欢迎您！If so much can be done in the city with binoculars, a telescope offers much wider possibilities. The Moon and planets show every bit as clearly to the urban astronomer as the rural one. True, a city is full of heat sources that can cause atmospheric turbulence and degrade the seeing. But often the city haze actually seems to steady the view. www.astroview.com.cn3 t0 |8 n4 p7 O* s  Y' v
Jim Phillips of Charleston, South Carolina, was one of many city observers who answered a request in Sky & Telescope for their stories. Phillips dedicates his observing time to the Moon and planets. "Quite honestly," he writes, "I am amazed at how many nights of good seeing I get from my 'middle of the city' location." He uses a custom-built 8-inch f/13 refractor in a roll-off-roof observatory behind his house. "I realized long ago that I was likely always to live in or near a city, and, after great thought, concluded that rather than a portable telescope I could take beyond the lights, I would prefer an observatory in a light-polluted area. To me the advantages of having an observatory with charts, books, and catalogs handy, and the ability to begin observing within minutes, far outweigh the light pollution and partially obstructed sky.
+ y( k' C3 N: G% a. d天文望远镜器材评测和交流论坛"I have split doubles at or near the theoretical limit of my telescope. Detail on Jupiter is excellent, as is detail on the lunar surface." Phillips ended up taking over the revived Lunar Dome Survey of the Association of Lunar and Planetary Observers.
' H  Q7 W( i" G3 M! K- U9 l' X天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪It doesn't take such a powerful telescope to overcome viewing problems. Robert W. Bethune of Grand Rapids, Michigan, used a 3 1/2-inch Questar for nearly two years "from the heart of Seoul, Korea, a city of many millions with both smog and light pollution. The compound where I lived was heavily lit, with several streetlights nearby plus bright lights on the walkways and in windows." Nevertheless, he writes, "the Moon was of constant interest. This past summer offered excellent opportunities to study the Jovian and Saturnian systems. There are a number of variable stars, double stars, and even nebulae that can be observed with practice through heavy pollution. My greatest success was timing the bright-limb occultation of an 8th-magnitude star during the recent Pleiades passage." 天文望远镜器材评测和交流论坛' V9 T- P  z  m. v( Z$ W
Bethune offers several tips: "One can be aggressive about certain lights. I dealt with offending sidewalk lights by simply opening them up and loosening the bulbs, remembering of course to restore them afterwards.

"It helps to retire late and rise early. Even in the biggest of cities, things slow down in the dead of night. Planning ahead also helps. One becomes skilled at digging into sky calendars and planispheres for events that will take place within one's limited hunk of sky. The most important lesson is to accept the limits of the situation, after careful experiment and investigation have revealed what they are." + Y  _4 I- M7 T- ]4 [4 o
Pointing a telescope out a window is supposed to be utterly taboo for anyone who aspires to the title of amateur astronomer. Temperature differences between outdoors and indoors are supposed to destroy the steadiness of the seeing. This is certainly true at times -- but not always, as Michael Boschat of Halifax, Nova Scotia, discovered. "For planetary work I stick my 3-inch refractor out the front window, and at times the images are so steady I can use 200 power. I did so for Mars last summer and saw markings even though the planet was low in the sky over a neighbor's roof."
4 _8 c+ v5 L" d& ?& _$ \* v4 oThen there's always the Sun. Sol Steinberg is a retiree living in a garden apartment complex near Camden, New Jersey. "My windows face east, into the 'garden' surrounded by 11 buildings." Using an inexpensive 3-inch reflector on a tabletop mount, he has photographed the Moon and followed the satellites of Jupiter and phases of Venus. "The Sun has become my regular morning subject," he writes. "The 55-mm eyepiece projects a bright image on my bedroom ceiling, but nothing equals direct viewing with a filter." He began following the comings and goings of sunspots. "A new group appeared yesterday, and this morning two of the spots have clearly become arcs -- a new and exciting phenomenon to me."
& h0 p+ u7 Q+ y- |2 M( q1 m, k+ ~www.astroview.com.cn...And the Deep Sky Too 天文家园欢迎您！1 \5 M8 S7 e4 T6 v/ B3 I$ L+ Q. O
Nebulae and galaxies, with their low surface brightnesses, are hit hardest by light pollution. Therefore many urbanites give up on them before really trying. One who refused to be defeated was Jenny Worsnopp near New York's Lower East Side. "Manhattan is the worst any amateur astronomer has to live with," she wrote. "But my great love is deep-sky objects. What to do?" The answer was to go out and give it her best shot. 天文望远镜器材评测和交流论坛3 f! D7 a" Q. O7 A
From her apartment's roof Worsnopp had an open view of the sky as well as such luminous spectacles as the Empire State, Chrysler, and Citicorp buildings. The last throws a brilliant fan of light toward the zenith as some architect's twisted notion of art. Nevertheless Worsnopp logged 46 of the 110 Messier objects from her roof using a 6-inch f/8 reflector. "The open clusters and bright globulars are visible even in the early nighttime," she wrote. Many buildings turn off their decorative lights at midnight, "and after that, the sky is ours. Sort of. 天文望远镜器材评测和交流论坛* W' y/ M: l5 A& }8 a
"I recently got a pleasant surprise. I went to the roof at 12:30 a.m. and found the galaxies M104, M66, and M81 -- and, amazingly, M97," a large, dim planetary nebula that can be difficult under any circumstance. "I used an OIII nebula filter and averted vision."
5 l: L: V/ O- S/ o3 [5 N! W6 c天文望远镜器材评测和交流论坛Such feats do require practice and skill, not to mention lengthy star-hopping from a naked-eye starting point that may be tens of degrees away. "City observing," Worsnopp comments, "is good training for those exotic objects that we all want to see from better sites. City observers don't look in their finders and see the Messiers glowing, waiting to be centered; we have to find the spot exactly, so it makes us good map readers. I guess my feeling is that if I can see it here, you, no matter where you are, can see it too."
) w$ V( E. M& `5 O* h. Q' `www.astroview.com.cnWorsnopp's tally is surpassed by that of David H. Frydman of London, England. "I have observed from cities for 30 years," he writes. Using a refractor "with a 5-inch f/5 Jaegers objective, I have observed 350 of 600 deep-sky objects that I know are possible (excluding double stars), most of them many times." He offers a number of pointers: www.astroview.com.cn) \! p( h; M6 z1 Z1 v
"There is a window with a radius of 25° from the zenith where faint objects are well seen even in London pollution. Every effort should be made to observe within this window, or at as high an elevation as possible.   K: d1 }5 r8 [, U
"Exclude as much local light as you can. Observe after 11 p.m., choose the most shielded site, and, if necessary, put an open box over your head and telescope. www.astroview.com.cn4 C  V0 }/ W- |5 C5 e) Q
"The best conditions are after rain and in high winds, as clear country air is blown over the city. During gales I have seen the Veil Nebula, the Owl Nebula M97 including its dark 'eyes,' and enormous detail in M33. Normally the first two are quite invisible in the 5-inch refractor." 天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪" H/ }; w8 @. h
Highly detailed charts, Frydman stresses, are essential. "You see one or even two magnitudes fainter if you know exactly where an object is and keep waiting until it comes into view."
9 n  S; o  U3 {" k天文望远镜器材评测和交流论坛The visibility of a deep-sky object in light pollution depends much less on its total magnitude than its surface brightness. So when looking through catalogs for promising targets, seek those that combine brightness with small size. 天文家园欢迎您！8 u- f6 q& b+ f
Many tiny planetary nebulae have quite high surface brightnesses. Alister Ling published a list of 60 "planetary nebulae visible from the city" in the now-defunct Deep Sky magazine (Summer 1986 issue). Many of them are practically starlike and require very high power to resolve -- not to mention excellent charts to identify them in the first place. Ling gives several tips for distinguishing them from stars. One method turns bad seeing to an advantage: a tiny planetary twinkles less than a star, for the same reason a planet twinkles less (both have appreciable disks). Another tip-off is an unstarlike greenish or bluish tint. - N1 B" k1 ]: A/ C5 H
The best "city planetaries" in Ling's list that are larger than 15 arcseconds across and brighter than magnitude 10.0 are not widely known: NGC 1535 in Eridanus, NGC 3242 in Hydra, and NGC 6826 in Cygnus. Clearly this is a big open field to explore. 6 N+ a$ Z# |! ?& l8 k" y/ m, Z
A more recent article on observing high-surface-brightness planetary nebulae in the city was published by Donald R. Ferguson in the April 1995 Sky & Telescope, page 96. Ferguson includes a list of 18 of these objects that he collected with a 3.5-inch telescope from within "the vast urban sprawl of Houston." 0 i& \$ N$ n3 H3 C$ H" ]
Nebula Filters 天文家园欢迎您！" \* ^+ H% l+ b% K
City and suburban observers gained a new claim to the deep sky when nebula filters were developed in the late 1970s. These function on a straightforward principle. Emission nebulae give off light at narrow wavelengths that differ from those of sodium- and mercury-vapor streetlights. By using a multilayer interference filter, the spectrum of visible light can be cut finely enough to separate these wavelengths. The result is a much darker sky, somewhat dimmer stars and galaxies, and only slightly dimmer planetary and emission nebulae. This enhanced contrast can, in many circumstances, more than make up for the relatively small amount of light lost from the nebula, and so it stands out more clearly.
  n0 t; y9 o2 W1 I& [6 P: RThese filters do not bring country skies to the city, but they do help. One technique for detecting nebulae, especially tiny planetaries, is "blinking" with the filter. Hold it at the eye and move it rapidly in and out of the line of sight; a nebula will blink relative to the surrounding stars. Alternatively, blinking can be done by tilting the filter back and forth while looking through it, since it loses its effectiveness when at an angle.
  r; m; ]0 Q! L; e* E. ?5 n) f0 \Several nebula (or "light pollution") filter designs are available. They use somewhat different strategies for different types of objects and conditions. A detailed review of them is in the July 1995 Sky & Telescope.

The CCD
- Y' r# ^  M8 ~1 t$ h0 q, L天文望远镜器材评测和交流论坛The biggest promise that technology holds out -- for those who can afford it in both money and time -- is the CCD camera. By 2000, CCD (charge-coupled device) cameras had taken over and vastly expanded high-end amateur astronomy, and their prices are declining every year. A CCD camera has two enormous strengths. First, the CCD chip is many times more sensitive to light than either your eye or photographic film. Second, it feeds a digitally recorded image from the telescope directly into your computer, where the image can be enhanced, analyzed, measured, and manipulated. 天文望远镜器材评测和交流论坛8 z% B; v" K  E; \- ^
The most important manipulation is the ability to subtract away an extremely light-polluted background, as if by magic, with hardly any loss of data. An 8-inch telescope can now record 15th- or even 16th-magnitude stars in the worst city light pollution or moonlight. This is several times fainter than the same telescope can show stars to the eye under black, mountaintop conditions!
3 u( a2 C3 q8 L! X国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材Drawbacks to CCDs include the very small field of view, the difficulty of aiming this field where you want, and problems of focusing. The equipment may be temperamental; the telescope mounting must be as rigid and controllable as for long-exposure astrophotography. And, of course, you're looking at a computer screen, not stars. It has been said that CCD astronomy is about working with equipment and computers, not skygazing.
. l& Q! W4 m! s9 r3 A! P  h7 o7 D天文望远镜器材评测和交流论坛The most important advance that CCDs represent is the science that can be done with the recorded images. For much of the 19th century, amateurs were almost on a par with professional astronomers in terms of the useful science they could do. Then amateurs fell very, very far behind -- but now CCD cameras in dedicated hands are making up some of this lost ground. Amateurs are discovering asteroids in great numbers, performing professional-quality variable-star studies, detecting the 19th-magnitude optical afterglows of gamma-ray bursts near the limits of the observable universe, taking spectra of stars and galaxies, imaging the planets more finely than was once thought possible, and much more. 天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪: ?# ~+ @, R3 v6 y
No machine, however, will ever replace the simplicity and delight of examining the stars directly, as a part of living nature. 天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪+ J2 r6 Z. r3 Z: s
Duck and Cover
; [. P. [8 p; }4 l天文家园欢迎您！"Light pollution" is the glow in the sky itself. It should not be confused with local lights that shine directly into the observer's eyes.
" k* Z! A* A! y* j9 W3 b$ S; \国内专业的天文望远镜器材评测和交流论坛，致力于如高桥、televue、tmb、ap、tec等顶级望远镜和附属器材Local lights are more aggravating but easier to defeat. Many observers have cooperative neighbors who turn off outdoor lights on request. A good way to break the ice on this issue is to offer views through your telescope. 天文望远镜器材评测和交流论坛" A  [7 G/ Q$ g
If you can't observe in the shade of trees or walls, you might rig a tarpaulin to shield your site. Max Wyssbrod lives in Lucerne, Switzerland, which he calls "the brightest country in Europe." His "cloth observatory" consists of four aluminum poles 10 feet long that fit into tubes cemented into the ground in a 10-foot square. The four walls are black cloth; guy ropes add stability. The whole rig, along with an 8-inch Schmidt-Cassegrain telescope, takes 15 minutes to set up. 天文论坛,天文,望远镜,天文望远镜,apo,ed,televue,tv,tmb,高桥,ap,tec,望远镜评测，望远镜测评,双筒望远镜，天顶，目镜，望远镜配件，赤道仪! A# x0 |5 t) F- ]7 V
Another strategy is to shield only your eye and the back end of the telescope. An old-fashioned photographer's black cloth or equivalent, or a cape that can be thrown up over your head, does the trick. Any telescope in bright local lights should also have a long dewcap or side shield to keep the light out of the tube. Eyepieces should have rubber eyecups.
, e3 L) f+ b3 N1 F  a6 V7 @8 S天文望远镜器材评测和交流论坛"I use a black hood, and blinders I made from cardboard fitted to each side of my face," writes Charles Haun of Morristown, Tennessee. "This works quite well."
) w2 J) G0 X: n+ |Hiding under cloth and wearing blinders may seem an ignominious way to experience the glories of the cosmos. But such is the garb that amateur astronomers shall increasingly wear as they march bravely into the future.   天文家园欢迎您！6 u) A. p1 ^0 Y: Y: l# V$ _
天文家园欢迎您！2 e7 K. f3 s0 ?1 _; d

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不错天文望远镜器材评测和交流论坛2 v4 ~; L3 _$ l+ D* l5 U
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