Tele Vue 3-6mm Click-Stop Zoom Nagler Eyepiece - 1.25
| Article number: | ENZ-0306 |
| Availability: | More on the Way to us |
| Delivery time: | More on the Way to us |
One of the best planetary eyepieces available anywhere: the 3mm-6mm Nagler ZOOM! This high performance, high- contrast, high power eye-piece is ready to take its place among the best plan-etary eyepieces available but with a "Nagler" twist. Al incorporated his proven "Nagler'' concept into a zoom, while optimizing for the performance factors critical to planetary observers; contrast, resolution and comfortable eye-relief. The Nagler Zoom is "tack-sharp" across its constant 50' apparent field, and throughout its 3mm-6mm focal length range, even in fast APO scopes. The 3mm-6mm Nagler Zoom is parfocal throughout its zoom range, parfocal with other Tele Vue 1 1/4 eyepieces and has a constant 1Omm eye-relief. Weight is only 0. 3 lbs.
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
And, as seemingly unbelievable as it all sounds, the design includes just 5 elements in 3 groups. In case you're counting, that's the same number of air-glass surfaces found in a Plossl or Ortho plus a Barlow! Why did we design this eyepiece? By dialing-in the best balance between magnification, exit pupil size, and atmospheric turbulence, the critical planetary observer con find the best possible image for the observing conditions. The new 3mm-6mm Nagler Zoom features Click Stops at 3, 4, 5, and 6mm, full multi-coating, blackened lens edges, folddown eyeguard, rubber gripring, safety undercut, anti-reflection threads and filter threads. May the "degrading zoom" myth rest in peace!
3mm-6mm Nagler Zoom Highlights
1. High Power 3mm-6mm Zoom Range with Click Stops
2. 50* Constant Apparent Field
3. Ideal Full-Field Sharpness Across Zoom Range
4. Comfortable, Constant 10mm Eye-Relief
5. 5-Elements/3-Groups, High index Glass, Full Multi- Coating
6. Parfocal Across Zoom Range and with Tele Vue 11/4" Eyepieces
7. FoId-Down Eyeguard, Rubber (Drip Ring, Safety Undercut
8. Anti-Reflection Threads and Filter Threads