Tele Vue 21mm Ethos Eyepiece User Manual

21mm ethos eyepiece instructions

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

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)