开吹TV NP101:从MPT到NP
Al Nagler从很久以前就对古老的Petzval结构发生了浓厚的兴趣，这是160年前由法国人Petzval设计的结构，4片结构，前后各2群，经典的Petzval结构是2组4片结构，存在胶合的镜片，但是Nagler改良并获得专利的结构是前后两群，4片分离的形式。 很多年以前Al Nagler有个梦想就是能够设计一只既可以满足低倍广视野深空和高倍行星目视观察，又可以满足深空摄影，还可能便携的4，5英寸的高水平折射镜子。
他把这种镜子形容为“Multi-Purpose-Telescope”，简称MPT,第一代MPT的规格相当惊人，5英寸口径F4,这在当时1982年，同样口径的折射镜子都是F11-F15的年代，这种F值实在吓人，不过这支镜子虽然配合Nagler设计的目镜在deepsky观察上获得了极大的成功，但是由于高昂的售价，以及高倍性能的不足，使得Nagler开始考虑设计一只口径4英寸左右，F值5左右的，价格不算昂贵的新MPT镜子，而第一代的MPT镜子则作为TV品质检测部门的目镜测试镜子一直存在到现在。
第二代的MPT在1984年推出，名字叫做Renaissance,这是只黄铜镜桶的，做工极为美丽的镜子，焦距550毫米，F5.5。
第二代的MPT Renaissance的高倍素质相当不错了，在286倍也可以获得很出色的行星像。
到了1988年，第三代MPT镜子Genesis诞生了，规格是500毫米F5,由于在后组镜片中采用了萤石玻璃，光学素质提高到了APO的水准。
1993年，TV推出了MPT的第4代SDF 540毫米F5.4,从规格上Al Nagler做了些让步，同时前后镜组中各采用了一片萤石镜片，光学水准较前代极大提高，真正步入了顶级APO镜子的级别。
1996年，第五代MPT镜子TV101面世，它的光学质量较前代更加提高，前组中的萤石玻璃被SD玻璃所取代，并且位置也移到了第一片，同时改进了镀膜水准，这一代开始，MPT镜子的色散水准完全可以和最顶尖的其他品牌相媲美，但是F值却小不少，像场大很多。
2001年推出的NP 101,这是最新一代MPT镜子，冠以Nalger的名字，和前代比，光学上完全不可见色散，镜桶长度也缩短了很多，装入专门的软包，可以直接携带入机舱。
2003年TV还推出了5英寸的NP镜子。
Petzval的结构镜子，固然有很短的焦距，但是镜桶最小长度却都大于焦距，这是结构所致，Petzval的后组镜片，其实有两个最主要的功能1缩短焦距2平坦像场。就Petzval结构的前组两片物镜焦距而言，实际焦距都比较长（后组相当于0.6X的减焦距镜子），所以色散容易得到纠正，这也是NP镜子可以做到无色散的原因。 好文，UP！
其实在其它领域P结构的镜子有很多的，我手上有一只120/1.9的镜头，就是典型的P结构，但是P的缺陷也是很明显，要做到大像圈的话，设计难度上会高一些，也不能做到太大的焦比！ Genesis SDF 的前组是一块普通ED， 不是萤石。前后两组都是焦比F11，后组在前组焦距的一半位置。
Televue Petzval的最大优势是焦比小，彗差，场屈控制的好。弱点是由於后组只有口径的一半，离轴亮度损失较大。 Genesis SDF 的前组是一块普通ED， 不是萤石。前后两组都是焦比F11，后组在前组焦距的一半位置。
Televue Petzval的最大优势是焦比小，彗差，场屈控制的好。弱点是由於后组只有口径的一半，离轴亮度损失较大。
查过了的确SDF的前组不是萤石，但是也不是普通萤石，而是来自于日本包谷光学玻璃提供的FK02超低色散玻璃，这种玻璃的特性相当于FP-153,属于高级的低色散玻璃。 np应该是同口径中最便携的镜子吧。 好像是的。 顶 np的像场边缘相差收得很好（这点使np很出名） np101和他兄弟np127的全部英文资料，规格。
np101： The new TeleVue NP101 represents our closest realization yet of the "ideal" multi-purpose/visual telescope. Its snap-to-focus and extremely sharp, flat-field are sure to take your breath away. It is also the best and toughest test platform to showcase all our new eyepiece introductions.
The successor to the Tele Vue-101 - The NP-101 (Nagler-Petzval) is more compact with the same 4-element, 540mm, f/5.4 specifications. The new scope is 4" shorter and feature both optical and mechanical enhancements over the previous model.
Features:
Telescope type: 4-element apochromat refractor using special dispersion glasses
Clear aperture: 101mm (4 inches)
Focal length: 540mm (21.3 inches)
Focal ratio: f/5.4
Resolution (visual): 1.1 arc-sec (Dawes limit for a 4" aperture)
Resolution (photo): 260 line pairs per mm
Field (35mm film): 2.5 degrees by 3.8 degrees (4.5 degrees diagonal)
Image scale: 2.7 degrees per inch
Magnification: 10x to over 250x using Tele Vue eyepieces and Barlows
Star diagonal: 2 inch, "everbrite" mirror type, with 1-1/4" inch adapter, both with brass clamp rings.
Focuser: 2 inch, rack and pinion type with brass clamp ring.
Mounting: Adjustable mounting ring with 1/4-20 tapped holes for standard (heavy-duty) photographic tripods or optional Tele Vue mounting systems
Weight: 10 lbs. O.T.A.
Length: 29", 26" O.T.A.
Accessories: Included as standard: custom-fitted case, screw-on lens cover, sliding dew/glare shield, 2" everbrite, 1 1/4" adapter.
Tube color: Ivory color powder-coated aluminum tube, black anodized lens housing, focuser assembly and mounting ring.
Aperture gain: 208 (compared to a 7mm exit pupil)
Dew Shield: Captive/Sliding, with Moisture Absorbent Lining
Mount Ring: Captive/Sliding with (3) ?20 attachment holes and 2 accessory slots.
Case: Custom Hard Shell std. Soft airline carrying bag as optional accessory.
np127：Custom NP-127 Hardshell Carrying Case featuring accessory storage in the lid and hand notches for a sure grip when lifting the scope. Case is the same size as the TeleVue NP-101 / -102.
Accessory storage area in hardshell case houses the standard 2" Everbrite star diagonal and 1-1/4" reducing adapter, plus three 1.25" eyepieces.
TeleVue is excited to bring a regular production telescope larger then 4" to market. TeleVue has been working on the NP127 for longer then you can imagine and they feel it is finally where TeleVue wants it both optically and mechanically. The NP127 certainly faces some stiff competition. However, TeleVue believes there is not another instrument that combines its fast f/5.2 focal ratio, 4 degree field and delivers all of TeleVue's acknowledged benefits. For the most discriminating refractor aficionado the NP127 is on the leading edge of apochromatic refractor technology.
Features:
OTA with sliding, captive dew shield
Included tube rings
Includes 2" Everbrite Star Diagonal and 2" - 1.25" reducing adapter
Includes custom fitted hardshell carrying case
Clear Aperture: 127mm (5")
Focal Length: 660mm
Focal Ratio: f/5.2
Visual Resolution 0.9 arc-sec.
Weight: 14 lbs. (O.T.A.)
Length: 33" (O.T.A.)
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