Kellner eyepiece

Kellner eyepiece

(kel -ner) See eyepiece.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Kellner eyepiece

[′kel·nər ′ī‚pēs]
(optics)
A Ramsden eyepiece with an achromatic eye lens.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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Includes 8-inch f/6 optical tube assembly with 1 1/4-inch focuser, 25-millimeter Kellner eyepiece, 6 x 30 finderscope, and Astrolight Altazimuth mount.
Each scope includes a 20-mm 1 1/4-inch Kellner eyepiece.
Included with all PSTs is a 12.5-millimeter Kellner eyepiece, which gives 32x.
PulsGuide retails for $39.95 alone, $119.95 with a 12-mm Kellner eyepiece and dual cross-hair reticle.
The 6-inch f/8 parabolic mirror comes with a Rigil QuickFinder, 18-mm Kellner eyepiece, rack-and- pinion focuser, and an instructional videotape, all for $379.
Edmund's 15-mm RKE (Rank Kellner Eyepiece) is nicer than most eyepieces supplied with a beginner's scope.
Rainbow Optics makes no claims for the Kellner eyepiece - which is a standard imported unit offered to observers who may not have a 1 1/4-inch ocular in their kits.
Optically, even when the scope was in good collimation, we soon learned to keep the power down and enjoy the views at 45x (using the supplied 25-mm Kellner eyepiece) and 90x.
I've found, for example, that a 9-mm Kellner eyepiece produces sharp, high-power views rarely attainable in my larger reflectors.
The telescope is shipped with two Kellner eyepieces, with focal lengths of 25 and 10 mm, yielding 26x and 65x respectively.
The COSMOS 90GT WiFi Telescope comes with a StarPointer red-dot finder, 25- and 10-mm Kellner eyepieces, and a rubberized accessory tray with an angled smartphone platform.
That said, it's worth noting that the scope's long focal ratio is very forgiving of eyepiece design, and I also had very good views with much older Plossl and orthoscopic eyepieces, and even lowly Kellner eyepieces delivered pleasing views.