User Manual

ManualsBrandsTele Vue ManualsOptics21mm Ethos Eyepiece

Tele Vue Optics, Inc., 32 Elkay Drive, Chester, NY 10918 845-469-4551

V12/3/2009

Thank you for purchasing the Tele Vue 21mm ETHOS, the eyepiece that

earned a 2010 Hot Product Award from Sky and Telescope magazine.

We wish you years of exciting deep sky viewing with the 21mm ETHOS, and we

welcome comments on your personal experiences.

21mm ETHOS EYEPIECE INSTRUCTIONS

Warning: Do not unscrew any sections of the eyepiece, as the lenses may fall out,

thereby voiding the warranty.

For Newtonians/Dobsonians, we recommend our

Paracorr coma corrector to eliminate the mirror coma

in f/5.5 or faster scopes. This permits the same kind

of full field sharpness routinely seen in Tele Vue’s

NP-Series refractors. You can use the 21mm

ETHOS 2" barrel in the Paracorr with the tunable top

at its full down position, Mark 5 (top mark on

Paracorr slot).

Note, the 21mm ETHOS nicely complements the

13mm and 8mm Ethos, since the power spacings

are 1.6x and the field area spacings are about 3x.

If you have eyesight astigmatism, you can add Tele

Vue’s Dioptrx Astigmatism Corrector to ETHOS,

instead of using eyeglasses, to get the sharpest view

possible (check dioptrx.com for more details).

Telescope Magnification (x) True Field (°) Exit pupil (mm)

TV-60is 17.1 5.8 3.5

TV-76 22.9 4.3 3.3

NP-101, NP-101is 25.7 3.8 3.9

TV-85 28.6 3.5 3.0

NP-127is 31.4 3.1 4.0

TV-102, TV-102iis 41.9 2.4 2.4

Tele Vue 21mm ETHOS Specifications

Apparent Field: 100º

Focal length: 21mm

Effective Field

Stop:

36.2mm

Eye Relief: 15mm

(accepts Tele Vue’s

Dioptrx astigmatism

corrector)

Barrel Size: 2" (accepts 2" filters)

Weight: 2.25 lbs.

Approximate dimensions of 21mm ETHOS

A. Length of barrel above reference surface (4.4")

C. Length of 2" barrel (1.6")

D. Diameter of black barrel (3")

F. Effective location of field stop (-0.37")

(Above Reference surface location of 2" barrel seat)

Summary of content (2 pages)

PAGE 1
Thank you for purchasing the Tele Vue 21mm ETHOS, the eyepiece that earned a 2010 Hot Product Award from Sky and Telescope magazine. We wish you years of exciting deep sky viewing with the 21mm ETHOS, and we welcome comments on your personal experiences. 21mm ETHOS EYEPIECE INSTRUCTIONS Warning: Do not unscrew any sections of the eyepiece, as the lenses may fall out, thereby voiding the warranty. Tele Vue 21mm ETHOS Specifications Apparent Field: 100º Focal length: 21mm Effective Field Stop: 36.
PAGE 2
To Assist in Building Your Collection Eyepiece Reference Data The Basics Telescope objective F.L. 1. Telescope Magnification = eyepiece F.L. 2. Exit Pupil: the circle of light where you place your eye. Exit Pupil Diameter = eyepiece F.L. telescope f/# 3. True Field of View: angle in sky in degrees. TFOV = eyepiece field stop dia. telescope obj. F.L. x 57.3° 4. Apparent field: the angle the field stop circle appears in your vision, when you look through the eyepiece.