转一片相当不错的文章，描述一个英国的双星/行星爱好者的发烧历程。
% q6 A  S9 C- V$ h$ N$ I- @  P9 X- mwww.astroview.com.cn可以看到mewlon的威力，以及几款经典镜子，比如intes和tak mewlon、fs的对比。天文家园欢迎您！: v/ w8 D2 {! k+ y

! a( t" D3 Z& |+ a' j2 k天文家园欢迎您！
5 |& _8 M  Y% g8 n$ [$ h* j0 Y天文望远镜器材评测和交流论坛
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  x& ]* j! ]  R1 l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- r  g/ Y: y' ]4 d
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Apo Refractor – Reflector – Mewlonwww.astroview.com.cn7 N' c. u+ T1 p/ F6 D& l2 j2 [

I have looked thro’ countless top end scopes and made direct comparisons at star parties. There is nothing quite like the view through a top end Apo refractor. There are two qualities which contribute to this: The lack of any central obstruction provides for a jet black background for which (the second quality) pinpoint star images across the Field of View (FOV) are superimposed upon. The rest of it, low contrast planetary and DSO detail,
) C6 H; j( l+ z4 |6 M8 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just falls into place (I’m assuming well baffled, excellent colour free optics, with smooth surfaces and low scatter etc.)
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My main interest used to be visual observation of Double Stars and the Planets and now that I live under the dark rural skies of Norfolk, DSO’s as well. For many years my goal and reason behind researching countless articles and comparing countless scopes was the ultimate planetary scope for visual observation from UK skies. But I didn’t have unlimited money to throw at it, so the solution had to offer value for money.天文望远镜器材评测和交流论坛/ u8 p* ^& x2 Y' ?$ P/ s8 T1 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  x$ @) ^; j' p' o
About 8 years ago I bought my first Mak-Newt, an Intes-Micro 7” Mak-Newt with 20% obstruction and 1/8th wave Pyrex optics. In A-B comparisons with a Tak FS152 at a starparty there was nothing to choose between them on visual views of Saturn and Jupiter. Of course the Tak is far better engineered, could do wide field photography (forget this with a Mak-Newt), has better thermal properties and looks the part! But from my point of view the Mak-Newt delivered what I wanted visually at about the 1/3 of the total price (including mounts.) If money was no object I’d have had the Tak instead. One of the things I could do with the Mak-Newt is to push the powers up high and get superb star images. My favourite was the double-double. At x540, you would get both pairs at the opposite edges of the FOV with perfect airy discs and diffraction rings and huge gaps天文望远镜器材评测和交流论坛( E: V8 x* l* U: s8 Y
between the airy discs. You would not get this with a normal Newtonian because of coma. People looking thro’ the scope would comment on the jet black background AND the pinpoint star images right to the edge of the field (again the qualities of a top Apo.) The other issue to consider is the central obstruction. At 20% you didn’t notice it directly at night time, but you can detect it’s effect at daytime. A good rule of thumb say’s everything else being equal (good optics, baffling etc) a reflector of a given aperture performs as well on low contrast features as well as an unobstructed scope of the same aperture minus the diameter of the secondary. On the 7” f6 Mak-Newt, this works out at 5.9”. Fast Reflectors with larger central obstructions have reduced contrast which generally shows up as a brighter background but these scopes also generally don’t have the same level of baffling. Collimation is more critical on fast reflectors which can be enhanced by poor engineering which shows itself in flexure. Poor collimation means less pinpoint star images in addition to the coma introduced by fast optics. (A long focal length reflector can give pinpoint images but then you run into mounting problems.)天文望远镜器材评测和交流论坛! S7 A: Q9 A5 G
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A year later, at the same starparty I had my first look through a Mewlon – Percy Kia’s 8” one. It was about 3am and a damp steady night with excellent seeing. I was gob smacked at how good the view of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- f0 J. z5 y2 O3 f7 m
Saturn was. Until then, apart from the 6” Apo’s I didn’t think anything else came close to the Mak-Newt on visual views of the planets. The big Dobs (with good optics) gave images that were washed out by being too bright – the seeing in the UK just not allowing sufficiently high powers. The 8” Mewlon, despite it’s open tube, 30% obstruction and thick secondary spider vanes came very close. Really sharp Cassini Division, excellent colour and low contrast detail in the ring system – a superb view. The contrast and sharpness of the image was superb and totally contrary to my ideas on a scope with a 30% obstruction.( |" ]) ~9 L) X9 H. B6 K0 H

3 _8 `2 }+ m6 T9 X天文望远镜器材评测和交流论坛Time moved on. I acquired an 8” f6 Mak-Newt (18.5% obstruction). I eventually sold the 7” f6 and 8” f6 Mak-Newts and purchased a special order Mak-Newt. 7” f8, 13% obstruction, Quartz 1/10th wave optics. I had decided this was the optimum aperture for visual planetary views from the UK. Larger aperture’s look thro’ too much atmospheric turbulence. This really is a superb planetary scope. It totally outperforms ANY 6” APO visually on the planets that I’ve compared it to and I would guess it probably approaches the performance of
  Z- v, U  ~2 ^9 x2 Y0 ]a 7” Apo. (I think it was Horace Dall who did a lot of work on central obstructions and came to the conclusion that below 15% it has no effect). Couple this with the excellent optics (Quartz polishes up really smooth and has excellent thermal properties) and it’s a real performer. Those who’ve looked thro’ it will confirm this.
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7 P4 p6 w5 G& f2 f+ O& c1 {+ nwww.astroview.com.cnIn the meantime a friend of mine, Martin Hopewell purchased a 10” Mewlon. I consider this to be the best value all round scope you can get. We regularly attend the same meet and have done countless A-B comparisons. On the planets in good seeing conditions there is nothing to choose between them. (Again the rule of thumb gives 10 – 3 = 7). In poor seeing, the Mak-Newt has a slight edge, probably due to it punching thro’ less turbulent atmosphere. But the 10” Mewlon, with it’s greater light grasp and excellent contrast outperforms the Mak on DSO’s. I’ll come to star images a bit later.( A; P; P  L0 g& k9 B
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1 u: H+ @9 y. e( i
My idea was to have the Mak-Newt for planetary and a 14” Newtonian for DSO’s. I purchased a 14” f4.6 Newtonian with 1/8th wave optics which I mounted Equatorially on my Russian Alter D6 mount. I only kept it 3 months. I have to say, the optics were good but I didn’t like the awkward positions I was getting into with the equatorial mount. I also didn’t like the flexure in the scope which meant that it went out of collimation when switching from one side of the mount to the other. Also on low contrast features on DSO’s, the 10” Mewlon wasn’t far behind. I remember doing A-B comparisons on the dark lanes on M31. I also didn’t like the coma in such a fast Newtonian (I’ve been used to a Mak-Newt.) The Dall-Kirkham design Mewlon does have coma off axis, especially compared to a Mak-Newt but not as much as a very fast Newtonian. I started thinking about the 10” Mewlon, excellent planetary views, high contrast images with black backgrounds (refractor like performance?) comfortable viewing position – you can sit at the back of the scope with a coffee in your hand as opposed to balancing up a step ladder, mmm…..
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This is why the 10” Mewlon is so excellent, at £4,500 it has superb all round performance yet you can mount it on a reasonable priced mount such as a G11 but with similar planetary performance I didn’t think the 10” one was worth the while over my 7” Mak-Newt. Why does the Mewlon have such high contrast, even with a 30% obstruction? The answer lies in it’s baffling and ultra smooth optics which you can get with a Dall-Kirkham cassegrain but are much more difficult to achieve in a classical design.天文家园欢迎您！8 ?$ s4 K9 P0 g2 b+ b

) B0 |' _/ ]+ \7 C# ~) m' ywww.astroview.com.cnI started drooling over a 12” Mewlon but at £10,500 in the UK, out of the question. I ordered a 14” SCT OTA for DSO’s with the view that the contrast might not be quite as good as the 14” Newtonian I had, but comfort of viewing would more than make up for this (Didn’t want a Dob – wanted it driven). As I did this, the only 12” Mewlon in the UK came on the Market second hand. It was 18 months old and had hardly been used. I went for it J, cancelling the SCT.
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# I! v( t- _0 R- D; M) |1 w天文望远镜器材评测和交流论坛

" d, j7 }1 |7 Q5 ~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Is the 12” Mewlon a significant leap in performance over the 10”? The answer is yes! But not only is the 12” over twice the price of a 10” new, normal mounts won’t handle it – the effective all up weight with tube rings, finder etc, etc, is about 75lbs. Forget G11’s and EQ6’s, you have to go to another level of mount. I was lucky in having the D6 mount which handles it fine for visual use, even at powers of x600 but most people purchasing a 12” Mewlon would want a more sophisticated mount for imaging. The Tak EM500 which is normally recommended for it is another £10,500 although you can get away with the NJP at over £6,000! This is why I say the 10” is such good value.
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6 W5 E- u9 l, r: A$ k天文家园欢迎您！Ok, performance. I was getting this as a quality well engineered, comfortable to use, driven scope for DSO viewing. I now only use the Mak-Newt for weekend trips (more portable – I can get away with a cheap EQ6 mount) and occasional double star viewing or my 16” Dobsonian for deep sky observing away trips.
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/ H1 Q$ P4 B6 ^& 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The 12” Mewlon not only totally outperforms the Mak on DSO’s but outperforms it on the planets. When I first got it, fortunately it was a night of excellent seeing. Martin Hopewell came over with his Zeiss bino-viewer and we had it at x700 on Saturn. Encke’s was clear and definite (gap not minima), colour and bands visible on the globe. Titan was observed as a disc! I looked at the Trapezium, which was past it’s best and there were 6 stars there, not 4 and glimpsing the E and F stars but they were there like there’s always 6 stars there! In nights of average seeing, I normally see 5 but ‘glimpse’ the 6th. (Remember – I’m at Latitude 52 degs).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* }4 S" e  v; W4 x% z

, W; K+ r8 e) D- d& w% x' Z5 Q天文家园欢迎您！During the 2005 Mars apparition I regularly observed at x480. It would take x575 on several occasions but I preferred x480. Visually observed Olympus Mons on several occasions and on one occasion, 2 of the 3 Tharsis Volcanoes as well. It takes high powers well.
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The contrast of the scope is superb, despite the central obstruction. I made A-B comparisons with an 18” f5 Dob (with an excellent 1/6th wave mirror) and a 20” f3.7 Dob on a reasonable dark sky. Although the images were brighter in the larger Dobs, the Mewlon showed just as much low contrast detail, in spiral structure in objects such as M51, M33 (and this was the owners of the Dobs saying this as well.) On very faint objects the larger Dobs won . The contrast and optics of the Mewlon are such that it gives a similar performance on DSO's to a good 16" Dob, with the added benefit of planetary and double star performance. If the object is really really faint then the larger Dob will have an edge. If it's a bright DSO such as M27 or M42 then the Mewlon wins – contrast. I also own a 16” Dob and find the two scopes compliment each other, the Mewlon being an observatory housed scope, the Dob an easily portable one. I think one reason for this is the ability to view say planetaries at high power (in excess of x300) driven and in comfort.
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$ p9 ~& b' o7 X! |4 @  {6 ~: |People who look thro’ it comment on the black background and pin point star images (refractor qualities again?). The best views I’ve ever had of M13 are through this scope. Bigger scopes show brighter images but the resolution and contrast excels in Mewlon 300.
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% U* F; e& b2 K& O6 b天文望远镜器材评测和交流论坛Onto star images now. One of the reasons refractors excel with star images is because of their relatively small size and thermal properties. A 4” refractor (I own an old Vixen 4” Flourite Apo – superb little scope which I mount on top of the Mewlon) will routinely achieve diffraction limited performance showing perfect airy discs and diffraction rings. A 12” scope of any configuration will rarely achieve diffraction limited performance in the UK i.e. you will rarely get airy discs and diffraction Rings with 12” scopes. Although laws of physics on aperture and resolution are insurmountable, under average UK skies a 6 or 7” scope will routinely outperform a larger scope on double stars showing nice airy discs compared to larger scopes with images flaring etc. This is why I sometime prefer the Mak-Newt on Double stars. However on good nights of seeing, the Mewlon again out performs. Several times I have viewed Zeta Bootes. This is a tight binary with relatively bright components of 4.5 and 4.6, currently separated by 0.65”! At x720 in the Mewlon I have observed perfect airy discs with a clear and distinct gap between them. I can just about detect a hint of elongation in the Mak-Newt. A couple of months ago, using the M300 I observed the ‘pup’ companion to Sirius for the first time in the UK for me. At the time the separation was 7 arc secs but with a 10 mag difference and low down (latitude 52 degs) this was quite an achievement.
0 H* B6 @+ I7 Z* W) L9 q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 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* f4 o, f: a; I7 i4 C1 C  B5 k! K
However when looking at star clusters (Globulars and M11 are simply stunning in this scope), the individual stars are much fainter than a big Dob and don’t ‘blob’ out. The resolution and contrast of the Mewlon still comes into play giving rise to the black background and pinpoint star image comments. The thermal properties of the Mewlon is pretty good with the side and rear plates coming off for cooling.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5 j9 j" d6 }9 o$ g

; ^6 N2 U" F8 f4 Q7 K  `& \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Doing A-B comparisons between the Mak and the Mewlon on planets in poor to average seeing conditions, the image in the Mak will appear steadier and sharper but you can still see more detail in the Mewlon.www.astroview.com.cn1 y) u( ~& w$ d% P
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All in all, for me, the Mewlon 300 is the ultimate all round amateur, observatory class visual scope without going to ridiculous expense.www.astroview.com.cn& G% F  J( F; f# l
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Andy Robertson.

伙计，你玩命转，问题是如我等这样的低E（nglish）q水准同好玩命看也看不明白。能否关键点上翻译一下，多谢了。

好，中午有空我翻一遍。: X+ h. T2 }2 b, V
工作先。

mewlon300上不起了，奔250还是可以的。业余玩也就到家了。

E文看得好辛苦啊

denebman兄谈起过小遮蔽高素质马牛和小一寸口径的apo目视行星是一个水平，不过北方的天气冬天马牛基本废了。

看不明白，很想知道Mewlon与同口径intes马卡的对比。

唉，现在是干什么、玩什么都离不开英文啊！想玩好了就必须把英语关过了，后悔当初不努力呀！

是得好好努力啊，虽然心里老想着要多学点E文，可工作以后就很难再静下心来学习

感觉原著中有一点点误区，谈到反差和镜筒内部发黑和消光关系很大；其实不然，这么做最多是降低了杂散光和内反射，夜空的背景看起来黑一些。如果镜面的精度和光洁度不够，低反差高空间频率的行星细节再怎么折腾镜筒也是看不到的（Astromart论坛上也有过讨论），我感觉Mewlon的优势主要还是高桥在精度上的保证，其次是采用大尺寸球面副镜的设计，使理论和实践走得比较近。
1 _* w( J' W2 _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天文家园欢迎您！# u0 z5 n. @3 }/ L# U
[ 本帖最后由 denebman 于 2008-1-10 13:02 编辑 ]

俺看CN上有人说过，mewlon250，MN86和AP155看行星都干不过10寸f8的牛反。当然也要高质量的镜面。原文我还记得，是说the 10" f8 blow all others away...

字好小，看得好累Copy下来到Word里放大点看，收了

mewlon250也差不多10寸了，怎么比不过10寸牛反？！那家的牛反啊？

为啥mewlon250就一定能比过牛反？f8的牛反中心遮挡可以小到15%，mewlon可是30％。哪家我就不知道了，估计zambuto啥的

牛反毕竟有它的缺点：镜子重，跟踪星不方便（当然好的牛反可以解决这个问题），无法进行摄影（配不上赤道仪）。。。。。。