Tele Vue 3.7mm Ethos Eyepiece - Manual (Page 2)

Tele Vue Optics, Inc., 32 Elkay Drive, Chester, NY 10918 845-469-4551 V10/6/2010
3.7mm ETHOS-SX 110° ORIGINS
Al Nagler eagerly pushed Ethos designer Paul Dellechiaie to extend the new 3.7mm focal length to
reach 110°, the same field as the LEM Simulator optics Al designed 45-years ago to train NASA
astronauts for lunar landings (See picture below). Years after the LEM program, the memory of the
110° view of the simulated lunar surface moving through the triangular cabin window of the LEM
inspi
red Al to develop an “Ultra Wide Angle” (his patent title) telescope eyepiece to approach that
“simulator experience.” When the 82° Nagler eyepiece hit the observing fields, it changed how amateur
astronomers viewed the heavens. An early customer dubbed
it a “spacewalk” view.
Essentially, “the experience” is about creating an image as natural as one sees with the unaided eye.
With Paul's help, Al's initial dream for amateur astronomers is now fully realized. The 3.7mm Ethos-SX
is designed and crafted to combine its exceedingly wide field of view with all the contrast, color-
rendition, distortion correction and center-to-edge sharpness needed to achieve that natural view.
Beyond the desire to simply achieve 110°, the extended field of view gave Tele Vue the ability to
produce a superb planetary eyepiece with a deep sky true field of view that logically fits within the rest of
the Ethos eyepiece line. With 110°, the Ethos-SX has 21% more AFOV area than the 100° Ethos
design. This permits a nice 62% power increase from a 6mm Ethos, while retaining 68% of its TFOV.
The 3.7mm actually has more TFOV than our 8mm Plössl, 6mm Radian, and 5mm Nagler Type-6!
We don't think we can aptly describe Al’s original experience of “flying over the moon,” but for the first
time, YOU can experience what the astronauts saw four decades ago.
Apollo Lunar Excursion Module (LEM) Simulator
Seen at left is one of the Infinity Display Projectors
that fit over the LEM simulator. A separate unit was
required for each window of the spacecraft. You
can see why the astronauts affectionately dubbed
the full collection of simulators for the Apollo
mission “The Great Train Wreck!”
The optical design consisted of a series of six-foot
mirrors, beam splitters, and a three-foot lens. It
took a televised image of the lunar surface along
with a separate background star field and projected
the combined image to infinity. The triangular
compressor lens (seen at left) was positioned
against the triangular window of the simulated LEM
cabin. The Infinity Display Projectors essentially
acted as giant 110º eyepieces, each with a 12” exit
pupil and 12” eye-relief. So, at one-foot from the
window, the astronauts saw a 110º field of view
through the windows corners.
And, you thought the new Tele Vue 3.7mm Ethos-
SX was big. Imagine that hanging off your
telescope!