TeleVue Plössl 55mm 50° Eyepiece - 2"

The 46mm Field Stop: Maximum True Field in a 2-Inch Barrel

The field stop is the ring inside the barrel that limits the field. Tele Vue's formula: True field = (field stop ÷ telescope focal length) x 57.3. With the 2" maximum of 46mm, the 55mm Plössl shows the most sky a 2" eyepiece can, the same true field as the 41mm Panoptic (also 46.0mm).

In a 2000mm Schmidt-Cassegrain it gives 36x and a 1.32° true field, room for the Orion Nebula with M43. In a 1000mm telescope the field is 2.6°, enough for the North America Nebula (NGC 7000) core or most of the Andromeda Galaxy (M31), which is about 3° long.

38mm of Eye Relief for Unmatched Viewing Comfort

The 55mm Plössl has 38mm of eye relief, well over the 15mm to 20mm recommended for observers who wear glasses to correct astigmatism.

• Adjustable Eyeguard: Tele Vue's Adjustable Height Eyeguard Adapter helps position your eye in the exit pupil, minimizing "pupil shadowing" and reducing stray light. Unscrew the upper part of the black metal eyeguard housing to the height you want, note where its bottom edge sits, bring the concealed lock ring up to that point and screw the housing down onto it. The soft rubber eyeguard can be used extended, rolled back or removed, and one portion can be extended to shield outside light.
• Dioptrx Compatible: It accepts DIOPTRX (Y in the chart), and astigmatism is likely to be visible with long focal length eyepieces that produce large exit pupils: a 55mm Plössl gives 5.5mm at f/10. You're more likely to see a sharper, higher contrast image with Dioptrx than with eyeglasses.

System Integration: Use with Barlows, Powermates, and Paracorr

Tele Vue makes Barlows and Powermates in 2x, 2.5x, 3x, 4x and 5x. A 2x makes the 55mm act like a 27.5mm.

For owners of fast Newtonian reflectors (f/5 or faster), coma can soften stars at the edge of the field. Tele Vue's Paracorr Type-2 eliminates coma, and scopes faster than f/5.0 see the greatest results. Its 1.15x factor only takes the exit pupil at f/4.5 from 12.2mm to 10.6mm, still over the 7mm limit for reflectors, so in fast reflectors a shorter eyepiece fits better.

Build, Focus and Care

The 55mm Plössl weighs 18.1 oz (513 g) and has an optical length of 4.8" (122 mm). Its sharpness comes from its patented design, multi-coatings and blackened lens edges. The barrel takes 2" (M48x0.75) filters, including BandMate filters. The warning is clear: "Do not unscrew the chrome barrel! The lenses will fall out, voiding the warranty." To clean the eyelens, unscrew the eyeguard housing, blow off dust with a bulb puffer, then use a Q-Tip moistened, not soaked, with Windex; never pour liquid on the lens.

A critical design note is the location of its field stop, which is near the bottom of the chrome barrel. This requires the focuser to be racked out further than with most other eyepieces. If your focuser cannot rack out far enough, Tele Vue strongly recommends its 2" Eyepiece Barrel Extender (EBX-2120), which makes the 55mm Plössl approximately parfocal with the 27mm Panoptic.

55mm Plössl vs. 41mm Panoptic: Choosing Your Low-Power Eyepiece

Both have a 46.0mm field stop in Tele Vue's chart, so they show the same true field; the 41mm Panoptic has a 68° apparent field at more magnification.

• Tele Vue 41mm Panoptic Advantage: More magnification and a smaller exit pupil: 5.9mm at f/7 against the Plössl's 7.9mm, and 27mm of eye relief.
• Tele Vue 55mm Plössl Advantage: 38mm of eye relief against 27mm, and a usable exit pupil in slower telescopes: 5.5mm at f/10 and 3.9mm at f/14.