The 2-4mm Nagler Zoom is recommended for fast, high performance scopes of 800mm focal length or shorter, such as the Tele Vue-60. It has click-stops every half-mm.
Concept / Background: I did not set out to design a zoom eyepiece, per se. David and I were discussing characteristics we'd like in a superior "planetary" eyepiece, and the zoom feature answered one of the major goals; how to obtain the highest possible useful magnification on a given night considering the ever-changing atmosphere. There were other aspects of equal importance and only the combination of all would satisfy our ethos in creating a "planetary" eyepiece: full field sharpness for any speed telescope, high contrast and transmission for natural color rendition, low scatter, and comfortable eye-relief. Being a zoom, we also concerned ourselves with making sure it was parfocal through the zoom range as well maintaining a constant apparent field of view. The one aspect we were not too concerned with was giving the eyepiece a wide AFOV.
Limiting the AFOV to 50° and the eye-relief to 10mm, we were able to create a compact physical design employing only five elements to reach the optical goals. Like other "Naglers," it utilized a negative lens group ahead of the focal plane. This permitted relatively long eye-relief for very short focal lengths. By independently moving the upper and lower lens groups, we achieved constant focus (parfocality), constant apparent field of view, and essentially constant eye-relief. Just by rotating the upper barrel, you can zoom through the power range. Click stops offer known power points for reference without needing to look at the barrel and instantaneously choose the optimum magnification for the given observing conditions.
I was sufficiently confident in the design and purposely decided to attach my name to the zoom, despite the common association between "Nagler" and 82° AFOV. I felt it was more important to stake our reputation on overcoming the "degrading zoom reputation" than maintaining the 82° assumption for "Nagler" designs.— Al Nagler
May 31, 2015
Great for planets at high magnificationPros:
Easy to Use,Quality LensesCons: Comments:
I have a complete set of orthos down to 4mm for viewing planets. Below that I was forced to barlow which is inconvenient when you need to start at high magnification and then back off as necessary. This quality eyepiece allows starting at high magnification at the 2mm setting (750x for me) and backing off to 4mm (375x for me) in half mm increments without swapping parts. Worth every penny.
This review was provided courtesy of AgenaAstro.comSort by
|Apparent Field of View||50°|
|Barrel Size||1.25" (31.7mm)|
|Bolt Case Included||Discontinued Item|
|Bolt Case Size||Agena 42x60mm|
|Max Width||1.7" (43.2mm)|
|Eye Relief by Design||10mm|
|Field Stop Diameter||1.7mm - 3.3mm|
|Filter Threads||Standard 1.25" Filter Thread (M28.5 x 0.6)|
|Rubber Eye Guard||Yes|
|Blackened Lens Edges||Yes|
|Eyepiece Focal Length||Variable Range|
|Eyepiece Field of View||51 - 60 degrees|
|Eyepiece Series||Tele Vue Nagler|
|Barrel Type||With safety undercut|
|Eyepiece Weight||5.70oz (161.59g)|