TeleVue ETHOS User manual

Tele Vue Optics, Inc., 32 Elkay Drive, Chester, NY 10918 845-469-4551
13mm ETHOS EYEPIECE INSTRUCTIONS
Warning: Do not unscrew any sections of the eyepiece, as the lenses
may fall out, thereby voiding the warranty.
Tele Vue 13mm ETHOS Specifications:
Apparent Field: 100º
Focal length: 13mm
Effective Field Stop: 22.3mm
Eye Relief: 15mm (accepts Tele Vue’s Dioptrx astigmatism corrector)
Barrel Size: 2" / 1¼"
Weight: 1.3 lbs.
Thank you for purchasing the Tele Vue 13mm ETHOS, the eyepiece that Sky and Telescope
magazine, in its October 2007 review called “A stunning optical achievement...” You can see the
entire review at televue.com, along with many star party evaluations, and an essay by Al Nagler
entitled “The Majesty Factor”. We hope that, after using ETHOS for awhile, you’ll comment on the
validity of this concept to explain the level of enthusiasm for ETHOS.
The 13mm ETHOS fits both 2" and 1¼" focusers or diagonals. Typically, in a 2" focuser, you will
focus “out” a bit (about 3/8" further than a 26mm Nagler Type 5), and in a 1¼" focuser, you’ll focus
“in” about ½" inch further than a 25mm Plössl.
Note: the in-travel may prevent focusing in some refractors when using the Tele Vue 60º Everbrite
diagonal, which has an unusually long optical path.
Since it is designed as an 1¼" eyepiece, there is NO optical benefit by using a 2" holder. The 2"
barrel is included just for convenience, but it is also threaded to accept our EBX-2120 2" extension
tube, which allows the use of 48mm filters.
For 1¼"holders:
1) Back off the lock screw in the 2" barrel section of the eyepiece so it can be fully inserted into the
holder.
2) If the holder has a lock screw, rotate the eyepiece so that the screw slips into the slot in the 2"
section of the eyepiece barrel. Your holder lock screw clamps to the 1¼" barrel of the eyepiece,
while the eyepiece lock screw clamps to the outside of your holder for maximum safety.
3) If your holder doesn’t have a lock screw, be sure to clamp the eyepiece lock screw onto the
outside of the holder. Please note that this eyepiece is heavy, and can fall out of holders with a
“slip fit” unless the lock screw is used!
For 2"holders:
1) Remove the eyepiece lock screw (Don’t lose it!)
2) Use the lock screw on your 2" holder, being careful not to let it slip into the slot in the 2" barrel
of the eyepiece.
3) The eyepiece will not “bottom” on Tele Vue 2" diagonals. Be careful if using diagonals by other
manufacturers.
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. See your Paracorr instruction sheet for proper setting.
Note: when using a 1¼" filter in ETHOS, be careful not to accidentally set the Paracorr’s tunable
top to its lowest setting, as the bottom of the filter might contact the Paracorr’s upper lens. It’s
best to thread a 2" filter onto the front of the Paracorr, or add our EBX-2120 2" extension tube to
the 2" barrel of ETHOS, for general use. For higher magnifications with a 100º field, use Tele Vue
Barlows and Powermates. When using ETHOS in 2" Powermates, use its 2" barrel.

Tele Vue Optics, Inc., 32 Elkay Drive, Chester, NY 10918 845-469-4551
Note: As with the Paracorr, do not use a 1¼" filter when using a 2X Powermate, as it will contact
the upper lens in the 2X Powermate. Again, the best solution is to use 2" filters in front of the
Powermate.
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).
We wish you years of exciting and Majestic deep sky viewing with ETHOS, and we welcome
comments on your personal experiences.
Telescope
Magnification (x)
True Field (°)
Exit pupil (mm)
TV-60, TV-60is
27.7
3.55
2.17
TV-76
36.9
2.66
2.06
NP-101, NP-101is
41.5
2.37
2.41
TV-85
46.2
2.13
1.86
NP-127is
50.8
1.94
2.50
TV-102, TV-102iis
67.7
1.45
1.51
Approximate dimensions of 13mm ETHOS
A. Length of barrel above reference surface (4.0")
B. Overall length below reference surface (1.6")
C. Length of 2" barrel (1.1")
D. Diameter of black barrel (2.5")
E. Depth of 1¼" barrel (1.1")
F. Approx. location of field stop (0.27")
Reference surface is location of 2" barrel seat