Zoomable 50° Constant Apparent Field Eyepieces - This is the "ultimate" tool for tweaking out the last bit of power that the atmosphere will permit!
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.
Lunt H-alpha Solar TelescopesLunt Double Stacked TelescopesLunt H-alpha Solar FiltersLunt Blocking DiagonalsAdapter Plates for Lunt FiltersLunt Ca-K Solar Telescopes and Modules
DayStar Quark Eyepiece FiltersDaystar H-alpha Solar TelescopesDayStar H-alpha ION FiltersDayStar H-alpha Quantum SE and PE SeriesSolar, C+D-ERF FiltersCoronado Solar Telescopes and Filters
White Light FiltersHerschel PrismsAccessories for Solar ObservingLunt and Coronado Solar EyepiecesLunt Dovetail BarsSolarscopes Card ModelsSundials
William Optics EyepiecesVixen Eyepieces and Barlow LensesCelestron Eyepieces & Barlow LensesBaader Eyepieces & Barlow LensesSky-Watcher and OVL Eyepieces and Barlow LensesExplore Scientific EyepiecesMeade Eyepieces and BarlowsOrion USA Eyepieces & Barlow LensesPentax Super-Wide Angle EyepiecesAPM Eyepieces and BarlowsVernonscope Eyepieces and Barlows
Lunt and Coronado Solar EyepiecesZoom EyepiecesSpecialist EyepiecesReticle EyepiecesRonchi Eyepieces
BinoviewersEyepiece and Accessory SetsEyepiece Bags and Cases2-1¼ AdaptersEyepiece ClampsRings and ExtendersEyepiece Accessories
