球状星团III

https://rogerivester.com/2012/06/23/m13-and-the-illusive-propeller/

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球状星团M13和难以捉摸的螺旋桨

巨大的球状星团M13位于夏季北半球观察者的头顶上方，可以欣赏极佳的风景。当我在1977年用我的4 1/4英寸f / 10反射镜观察该星团时，我能看到的最多是一个中等亮度**的未分解恒星球。**

在用小型反射镜观察M13的同时，我没有意识到切入仪表板SE边缘的三个暗道，即螺旋桨。那时我还没有听说过螺旋桨，但是这个范围太小了，看不到这个非常微弱的功能。但是，三十二年后的2009年5月，我使用了更大的望远镜，看到了螺旋桨。

可以将10英寸望远镜视为看到此最独特功能所需的最小光圈。如果您打算观察“难以捉摸的螺旋桨”，则最佳放大倍数约为200倍。

由于“ 深空奇观”（Deep-Sky Wonders）专栏作家兼作家沃尔特·斯科特·休斯顿（Walter Scott Houston）提出观察者寻找它，螺旋桨挑战似乎变得很流行。休斯顿在1953年7月的《天空与 望远镜》杂志上首次撰写了有关螺旋桨的文章。多年来，他多次提出了这一建议，但是直到最近，螺旋桨才在业余天文学界引起了广泛关注。

Rosse勋爵在1850年代提到了三场黑暗裂痕，TW Webb在“ 通用 望远镜的天体 ”中指出，布法姆使用9英寸反射镜看到了车道。

约翰Bortle看见车道在1980年采用12.5英寸的反射器，和丹尼斯·迪·西科与12英寸的f / 17波特转动架望远镜Stellafane期间于1981年。（来源看见他们很容易：“ 深空Wonder的 ”沃尔特·斯科特休斯敦，斯蒂芬·詹姆斯·奥梅拉（Stephan James O’Meara）的选集和评论 ，马萨诸塞州剑桥的 Sky Publishing Corporation

在2009年5月，我能够同时观察到带有10英寸和12英寸反射器的螺旋桨。我对12英寸长的星团的观察来自北卡罗来纳州南部山脉的南部边缘。我认为该网站的NELM为6.5，非常好，甚至在一个美好的夜晚也可能会更好。

在黑暗的地方，使用12英寸f / 5反射镜就很容易看到螺旋桨。但是，从我的中等光线污染的后院使用10英寸f / 4.5反射镜（NELM为5.0或更小），很难看到螺旋桨。

拉斯维加斯的弗雷德·雷沃思（Fred Rayworth）和瑞安·罗杰斯（Ryan Rogers）使用16英寸的反射镜，放大倍数为203x，可以轻松看到螺旋桨。

下面的草图是使用12英寸f / 5反射镜制作的，距北卡罗莱纳州西部南部南部山脉的南部边缘190倍。该草图是使用2号铅笔和空白的5 x 8便签卡制作的。使用扫描仪将颜色反转。

下图是夏威夷的James Dire博士使用190毫米Orion Maksutov-Newtonian拍摄的。

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Globular Cluster M13 And The Elusive Propeller

The great globular cluster, M13 is located high overhead for observers in the northern hemisphere during the summer, allowing for excellent viewing. When observing this cluster back in 1977 with my 4 1/4-inch f/10 reflector, the most I could see was a moderately bright ball of unresolved stars.

While observing M13 with the small reflector, I was unaware of the three dark lanes cutting into the SE edge of the cluster, called the propeller. I had never heard of the propeller at that time, but this scope was far too small to see this very faint feature. However, thirty two years later, in May of 2009 using a much larger telescope, I would see the propeller.

A 10-inch telescope might be considered the minimum aperture required to see this most unique feature. If you have plans to observe the “elusive propeller” a magnification of around 200x seems to be the optimum magnification.

The propeller challenge seemingly became popular due to Walter Scott Houston, columnist and writer of “Deep-Sky Wonders” suggesting that observers look for it. Houston first wrote about the propeller in the July 1953 edition of Sky & Telescope magazine. He brought it up several more times through the years, however, it has been only in recent times that the propeller has gained much attention in the amateur astronomy community.

Lord Rosse mentioned three dark rifts in the 1850’s, and T.W. Webb in “Celestial Objects for Common Telescopes” noted that the lanes were seen by Buffham, using a 9-inch reflector.

John Bortle saw the lanes in 1980 using a 12.5-inch reflector, and Dennis di Cicco saw them easily with the 12-inch f/17 Porter turrent telescope during Stellafane in 1981. (Source: “Deep-Sky Wonder’s” By Walter Scott Houston, selections and commentary by Stephan James O’Meara. Sky Publishing Corporation, Cambridge Massachusetts)

In May of 2009, I was able to observe the propeller with both a 10 and 12-inch reflector. My observation of the cluster with the 12-inch came from the southern rim of the South Mountains in North Carolina. I would rate this site as very good with a NELM of 6.5, and maybe even better on an excellent night.

The propeller was fairly easy to see with the 12-inch f/5 reflector from a dark site. Seeing the propeller, however, proved very difficult using a 10-inch f/4.5 reflector from my moderately light polluted backyard with a NELM of 5.0 or slightly less.

Fred Rayworth and Ryan Rogers of Las Vegas were able to see the propeller fairly easily, using a 16-inch reflector with a magnification of 203x.

The following sketch was made using a 12-inch f/5 reflector at 190x from the southern rim of the South Mountains in western North Carolina. The sketch was made with a No. 2 pencil and a blank 5 x 8 note card. The colors were inverted using a scanner.

The following image was taken by Dr. James Dire of Hawaii, using a 190 mm Orion Maksutov-Newtonian.

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M92大力神的球状星团和“麻烦号的钩子”

*观察员挑战赛完整报告：单击以下链接： 2016年7月观察员挑战– M-092*

*以下是芬兰Jaakko Saloranta的作品和素描，他是当今世界上最有才华和最有才华的视觉观察者之一。罗杰·艾维斯特*

*梅西耶92*

*梅西埃13号的小弟弟。星团中最亮的恒星是12.1级，因此很容易解决。但是，这是一个困难的肉眼物体：在57度的高度下几乎看不到最佳的避开视线。用8×30双筒望远镜很容易看到，是非星状的污迹。*

*与两个十等星形成一个三角形。使用3英寸折射器@ 133x（23’），可以实现部分分辨率–仅可见少数恒星。配备4.5英寸SkyQuest XT @ 152x（20′）时，M92分辨率相当好，可见几十颗恒星。明亮的核可能看起来略呈椭圆形，但可能只是核的未解决恒星NW引起的幻觉。*

*梅西埃92号有一个鲜为人知的小特征，绰号为“特劳弗洛特的钩子”（以19世纪法国天文学家埃蒂安·莱奥波尔德·特劳弗洛特命名）。它是钩状的恒星链，两边都有暗色海湾。该功能在Trouvelot制作的两个单独的草图中可见。第一个是1874年，第二个是1877年。M92的两个草图均来自哈佛大学天文台。*

*看到Roger Ivester在M92上的注释后，很明显Roger注意到了-至少是“ Trouvelot的钩子”的一部分。他将其描述为“一条由四颗恒星组成的微弱链，紧贴着扁平边缘”。这是Trouvelot绘制的完全相同的链的一部分！我个人无法分辨罗杰（Roger）勾勒出的黑暗道路。我只看到了几颗明亮的恒星，它们只是星团核心的E。*

*芬兰Jaakko Saloranta的铅笔素描：*

*以下是法国天文学家Trouvel0t绘制的草图。第一次是在1874年，第二次是在1877年，都是由哈佛大学天文台制造的。*

*下图：1877年Trouvelot绘制的草图*

*以下信息和作者的铅笔素描。RI*

*M92 – NGC 6341 –大力神的球状星团：* *日期：2016年5月27日*

*望远镜：10英寸f / 4.5赤道反射镜*

*目镜：11毫米–使用2.0* *倍增倍镜的****其他观察结果*
\放大倍率：间歇地104倍和208倍

*明亮，具有强烈的圆形核心和104倍的颗粒状纹理。当将放大倍数提高到208x时，外围区域和光晕中的恒星具有出色的分辨率，并且有许多异常值。*

*整体形状具有微妙的NS伸长率。NNE-WSW边缘是平坦的，这是群集中较引人注意和可识别的功能之一。当使用避开视线时，四颗星的模糊链会沿着扁平边缘出现。在观测的三晚中的两晚中，这些恒星是不可见的，并且是间歇性的或不恒定的。*

*以下是使用5 x 8空白便签卡的铅笔素描，其中使用扫描仪将颜色反转。请注意，无论是我的素描还是吉姆·迪尔（Jim Dire）的图像，星团东部都隐约可见星链。这对我来说非常困难，需要避开视线，并且只能在观察的第三天晚上间歇地看到。*

*罗杰·艾维斯特*

*M92：以下图片和文字来自夏威夷的詹姆斯·迪尔（James Dire）*

*James Dire博士*

*M92是位于大力神星座中的三个球状星团的大小和亮度的中间值。最明亮，最大的是M13，而我们天空中最小的是NGC6229。可以使用8英寸或更大的望远镜监视所有三个球状星团。*

*球状星团是由数万到数百万个恒星组成的高度紧凑的群。这些星团中大约有150个在我们的银河系周围形成了球形的光晕。还已知球状星团存在于其他星系中。仙女座星系可能是银河系的2-3倍。*

*M13是北半球可见的最亮的球状星团，也是地球上可见的第三亮的球状星团。大小为5.8，直径为25弧分，几乎与月球一样大。相比之下，在6.4级时，M92的亮度大约是其一半。跨度为15弧分。尽管两者都出现在查尔斯·梅西耶（Charles Messier）的著名目录中，但他没有发现它们中的任何一个。埃德蒙·哈雷（Edmond Halley）在1715年发现了M13，约翰·博德（Johann Bode）在1777年发现了M92。*

*M92被发现在基斯通最东北的恒星Pi Herculis以北六度和三分之一度处。与M13一样，M92可以很容易地在50mm双筒望远镜或取景器望远镜中进行监视。使用望远镜可以在两个星团中分辨出许多恒星。较大的孔径将揭示出更多的独立恒星。我建议目镜的屈光度为100倍，如果视线稳定，则可以更高。*

*在9.4级，要找到NGC6229比M92更具挑战性。NGC6229位于大力神俱乐部中心正北，或M13以北11度。最容易找到它的方法是将第5级恒星42 Herculis置于目镜中心，并向东南跳跃2度。威廉·赫歇尔（William Herschel）于1787年发现了NGC6229。六年后，他还是第一个在M92中分辨恒星的人。*

*我的M92图像是用10英寸f / 6牛顿镜和Paracorr II昏迷校正器拍摄的，焦距为1753mm。瞄准镜位于派拉蒙ME德国赤道仪的顶部，图像是使用SBIG ST-2000XCM CCD相机拍摄的。曝光时间为20分钟。视场中最亮的恒星，在星团的左侧（东侧），是HD156821，其辐射强度为9.76。左边的微弱恒星是16.1级恒星。星团东北侧的黄橙色星为HD156873，星等为9.98。该星团右下方的第三颗最亮的恒星以10.9级的亮度发光。这些星星都不是M92的成员。詹姆斯·迪尔*

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M92 Globular Cluster in Hercules and “Trouvelot’s Hook”

*The Observer’s Challenge complete report: Click on the following link: JULY 2016 OBSERVERS CHALLENGE – M-092*

*The following write-up and sketch by Jaakko Saloranta of Finland, one of the most talented and gifted visual observer’s in the world today. Roger Ivester*

*Messier 92*

*The baby brother of Messier 13. Brightest star in the cluster is magnitude 12.1 so it is fairly easy object to resolve. However, it is a difficult naked eye object: barely visible with optimal averted vision at an altitude of 57 degrees. Easily visible with a 8×30 binoculars as a non-stellar smudge.*

*Forms a triangle with two 10th magnitude stars. Partial resolution is achieved – only a handful of stars visible – with a 3 inch refractor @ 133x (23′). With a 4.5 inch SkyQuest XT @ 152x (20′) M92 appears as fairly well resolved, with a few dozen stars visible. Bright core, might appear slightly elliptical but is probably just an illusion caused by unresolved stars NW of the nucleus.*

*Messier 92 contains a little known small feature nicknamed “Trouvelot’s Hook” (named after 19th century French astronomer Étienne Léopold Trouvelot) . It is a hook-shaped chain of stars with dark bays at both sides. The feature is visible in two separate sketches made by Trouvelot. The first one is from 1874 and the second from 1877. Both sketches of M92 are made from Harvard College Observatory.*

*Having seen Roger Ivester’s notes on M92, it is obvious that Roger has noted – at least a part of – “Trouvelot’s hook”. He described it as “a faint chain of four stars follows the flattened edge”. This is part of the very same chain sketched by Trouvelot! I personally could not make out the dark lane sketched by Roger. I only saw a couple of bright stars just E of the cluster’s core.*

*Pencil Sketch By Jaakko Saloranta of Finland:*

*The following sketches by French Astronomer, Trouvel0t. The first one was made in 1874 and the second 1877, both from the Harvard College Observatory.*

*Below: Sketch by Trouvelot in 1877*

*The following information and pencil sketch by the writer. RI*

*M92 – NGC 6341 – Globular Cluster in Hercules:* *Date: May 27, 2016*

*Telescope: 10-inch f/4.5 Equatorial Reflector*

*Eyepiece: 11 mm – Also Other Observations With The Employ Of a 2.0x Barlow*
*Magnifications: 104x and 208x intermittently*

*Bright with an intense round core and a granular texture at 104x. When increasing the magnification to 208x, excellent resolution of stars in the outer regions and in the halo, with many outliers.*

*The overall shape has a subtle N-S elongation. The NNE-WSW edge is flat, which is one of the more noticeable and recognizable features of the cluster. When using averted vision a faint chain of four stars follows the flattened edge. These stars were not visible on two of the three nights of observations, and appeared intermittent or not constant.*

*The following is a pencil sketch using a 5 x 8 blank notecard, with the colors inverted using a scanner. Please note the faint star chain on the eastern side of the cluster, on both my sketch and Jim Dire’s image. It was extremely difficult for me, requiring averted vision, and could only see intermittently on the third night of observations.*

*Roger Ivester*

*M92: The following image and text by James Dire of Hawaii*

*James Dire, Ph.D.*

*M92 is the middle in size and brightness of three globular cluster located in the constellation Hercules. The brightest and largest is M13 while the smallest in our sky is NGC6229. All three globular clusters can be spied with an 8-inch or larger telescope.*

*Globular clusters are highly compact groupings of tens of thousands to millions of stars. There are approximately 150 of these clusters forming a spherical halo around our Milky Way galaxy. Globular clusters are also known to exist in other galaxies. The Andromeda galaxy probably has 2-3 times as many as the Milky Way.*

*M13 is the brightest globular cluster visible in the northern hemisphere and the third brightest visible from Earth. At magnitude 5.8, has a diameter of 25 arc minutes, nearly as large as the Moon. In comparison, at magnitude 6.4 M92 is roughly half as bright. It spans 15 arc minutes. Although both appear in Charles Messier’s famous catalog, he did not discover either of them. Edmond Halley discovered M13 in the year 1715 and Johann Bode discovered M92 in 1777.*

*M92 is found six and one-third degrees north of Pi Herculis, the northeastern-most star in the Keystone. Like M13, M92 can easily be spied in 50mm binoculars or finder scopes. Many stars can be resolved in both clusters using telescopes. Larger apertures will reveal more individual stars. I recommend eyepieces that yield 100x, or higher if the seeing is steady.*

*At magnitude 9.4, NGC6229 is quite a bit more challenging to find than M92. NGC6229 is located just north of the center of Hercules’ club, or 11 degrees north of M13. The easiest way to find it is to center the 5th magnitude star 42 Herculis in the eyepiece and hop two degrees to the southeast. William Herschel discovered NGC6229 in 1787. He was also the first to resolve stars in M92 six years later.*

*My image of M92 was taken with a 10-inch f/6 Newtonian with a Paracorr II coma corrector yielding a 1753mm focal length. The scope was atop a Paramount ME German equatorial mount and the image was taken with an SBIG ST-2000XCM CCD camera. The exposure was 20 minutes. The brightest star in the field of view, left (east) of the cluster, is HD156821 shining at magnitude 9.76. The faint star to the left of this is a 16.1 magnitude star. The yellow orange star on the northeast side of the cluster is HD156873, magnitude 9.98. The third brightest star in the field, to the lower right of the cluster shines at magnitude 10.9. None of these stars are members of M92. James Dire*

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挑战者列表

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