Nearly half a century ago, Al Nagler designed the optics for the LEM (Lunar Excursion Module) simulator that was used to train NASA astronauts how to land on the Moon during the Apollo program. From Apollo 11 through Apollo 17, every astronaut pilot who landed on the Moon trained using Al’s optics to learn how to do it.
Years after the LEM program ended, the memory of the 110° view of the simulated moving lunar surface seen through the triangular cabin window of the LEM simulator inspired Al to develop an “Ultra Wide Angle” telescope eyepiece to approach that lunar landing “simulator experience.” That eyepiece was the famed 82° field Nagler. When the first Nagler hit the observing fields, it changed forever how amateur astronomers viewed the heavens. An early customer dubbed it a “spacewalk” view.
But the 82° Naglers, and even the recent 100° field Ethos eyepieces, didn’t duplicate the original 110° LEM simulator experience Al remembered. So Al pushed Ethos designer Paul Dellechiaie to extend the field of the Ethos design to reach a full 110°, the same astonishing field as the LEM simulator. The result is the 3.7mm Ethos-SX (Simulator eXperience) eyepiece – a Sky & Telescope Hot Product for 2011.
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 TeleVue 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 a 110° field, the Ethos-SX has 21% more apparent field of view area than the 100° Ethos design. This permits a nice 62% power increase from a 6mm Ethos, while still retaining 68% of its true field of view. The 3.7mm actually has more true field of view than a TeleVue 8mm Plössl, 6mm Radian, or 5mm Nagler Type 6!
The 3.7mm is a 1.25" format eyepiece and is parfocal with a wide range of 1.25" TeleVue Plössls, Panoptics, Radians, Naglers, Nagler Zooms, and 6mm and 8mm Ethos eyepieces. It can be used with the TeleVue DIOPTRX eyesight astigmatism corrector. The included screw-on 2" adapter lets you use the 3.7mm Ethos-SX in a 2” star diagonal or focuser and is designed to make the eyepiece parfocal with the 13mm and 10mm Ethos eyepieces when they are used in their 2" modes.
We don't think we can aptly describe Al’s original experience of “flying over the moon” in the LEM simulator, but for the first time, YOU can experience what the astronauts saw four decades ago. For example, with a TV-85 refractor (or any similar 600mm focal length scope), the actual field of view is 0.67°, so that the entire full Moon fits into the eyepiece field – but at a magnification of 162x! Talk about getting up close and personal with the lunar surface!