Tele Vue 13mm Ethos Eyepiece - Manual

Tele Vue Optics, Inc., 32 Elkay Drive, Chester, NY 10918 845-469-4551 V4/3/200
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. You can use the 13mm ETHOS 2" barrel in the Paracorr with the
tunable top raised to its maximum, mark 1 on Paracorr slot. However, you can get closer to ideal
coma correction by using the 13mm ETHOS in a high-hat 2" to 1¼" adapter (part ACR-2125 or satin
finish ASF-8125) and setting the Paracorr to its full down position, mark 5 on Paracorr slot.