Focal Length:  21mm
Apparent Field:  100°
Eye Relief:  15mm
Effective Field Stop Dia.: 36.2mm
Barrel Size:  2"
Weight:  2.25 lb.

Some Holes Just Need to be Filled!

The 10mm Ethos delivers: 100° apparent field (50% larger in area than 82° Naglers), comfortable eye-relief, (accepts DIOPTRX eyesight astigmatism correctors), distortion correction, high contrast and on-axis sharpness for planetary viewing. It is the “do-it-all” eyepiece perfect for all scopes that can utilize this focal length. And, "filling the hole" between the 13mm and 8mm makes it the ideal centerpiece for a 17mm/10mm/6mm Ethos set.

An important benefit of the combination of large apparent field of view and shorter focal length is that for a given field in the sky, higher magnification results in a darker sky background. Fainter stars become visible and more detail is seen on all deep sky objects. Ethos provides another big magnification/contrast jump, yielding dramatic views simply not previously possible in any telescope. With the smaller exit pupil, eyesight limitations are also reduced.

In addition to matching all the key performance criteria of its 13mm sibling, its lighter weight and smaller diameter makes the 10mm more suitable for use with a binocular viewer.

Tele Vue 10mm Ethos Specifications

•  Apparent field: 100°
• Focal length: 10mm
• Effective field stop diameter: 17.7mm
• Eye relief: 15mm (accepts DIOPTRX eyesight astigmatism corrector)
• Barrel size: 2"/1¼"
• Black barrel diameter: 61 mm
• Weight: 1.10 lbs (17.7 oz.)
• Availability: in-stock

Celebrate the start of the International Year of Astronomy 2009, the 400th anniversary of Galileo's first use of an astronomical telescope, by showing friends and neighbors the best of our wonderful universe. The Tele Vue philosophy (Ethos, if you will) has always been about inspiring “spacewalk” vistas by creating the finest “rich field” refractors and wide angle eyepieces. We hope the introduction of these new Ethos models will further rekindle the appreciation of astronomy and support all the worthy goals of IYA 2009. It’s been quite a challenge to develop new Ethos eyepieces to the same performance standards achieved by the 13mm and 8mm models, perhaps the most honored in history. We hope the increased field of the 17mm and increased power of the 6mm will open up new visual experiences that Galileo could hardly have imagined, from small refractors to the largest Dobsonians. 17mm Ethos Specifications Apparent field: 100° Focal length: 17mm Effective field stop: 29.6mm Eye relief: 15mm (accepts DIOPTRX eyesight astigmatism correctors) Barrel size 2” Weight: 1.55 lbs (24.8 oz.) 6mm Ethos Specifications Apparent field: 100° Focal length: 6mm Effective field stop: 10.4mm Eye relief: 15mm (accepts DIOPTRX eyesight astigmatism correctors) Barrel size: 2”/1¼” Weight: .97 lb/15.5 oz.

At NEAF 2008 we were pleased to demonstrate a new 8mm focal length, 100° AFOV Ethos eyepiece. In addition to matching all the key performance criteria of its 13mm sibling, the new 8mm version is parfocal in 1¼" focusers with Radians, Plössls, Type 6 Naglers and 1¼" Panoptics. Further, its lighter weight and smaller diameter than the 13mm Ethos makes the 8mm suitable for anyone using a binocular viewer. Another application is for spotting scope set-ups with the Tele Vue 60° 1¼" diagonal. In comparing it to our 8–24mm Zoom eyepiece, the 8mm Ethos has the power of the 8mm Zoom and 83% of the field of the 24mm setting! Apparent field: 100° Focal length: 8mm Effective field stop diameter: 13.9mm Eye relief: 15mm (accepts DIOPTRX eyesight astigmatism corrector) Barrel size: 2"/1¼" Black barrel diameter: 53.4mm Weight: 0.95 lbs (15.2 oz.)

Ethos 8mm Announcement Video

Cloudy Nights video from NEAF 2008

Tele Vue 13mm Ethos™ Tele Vue is known for its in-house eyepiece and telescope designs by Al Nagler; our latest eyepiece brings new meaning to the term “in-house.” The concept for this eyepiece was first proposed by Tele Vue President David Nagler, with performance parameters giving it the fundamental characteristics (the ethos) of a Tele Vue eyepiece: high contrast, comfortable eye relief and full field sharpness. Control of astigmatism, field curvature, lateral color, angular magnification distortion correction (technical reference), and low pupil sensitivity for daytime use were specified criteria. Following Tele Vue’s philosophy of pushing the state of the art, long-time Tele Vue employee and optical design protégé Paul Dellechiaie took up the challenge and designed the basic eyepiece form. Under Al’s guidance, Paul tweaked his design to fulfill the original goals. While sharpness is inherent to the optical design, contrast is maximized through the intelligent use of flat finished baffles and ultra low reflectance, high efficiency coatings tuned to the composition of each element. At the 2007 Northeast Astronomy Forum, Tele Vue once again broadened the amateur astronomer's perspective on the universe and introduced a new observing experience; 100º of pure Tele Vue quality. With a 13mm focal length evoking the original “Nagler” revolution, the field area of this new eyepiece is more than 50% larger than an 82º field. The Tele Vue Ethos is essentially multiple eyepieces, delivering the true field size of a longer focal length, narrower apparent field eyepiece with the benefits of higher power and darker sky background. We invited NEAF attendees to take a look and see the universe the way we think it was meant to be experienced, with a field of view incredibly wide and sharp! We were very pleased indeed by the response and validation of our design goals. Tele Vue 13mm Ethos Specifications Apparent Field: 100º Focal Length: 13mm Effective Field Stop: 22.3mm Eye Relief: 15mm (accepts DIOPTRX™ eyesight astigmatism corrector) Barrel Size: 2”/1¼” Weight: 1.3lbs. / 20.8oz

At Tele Vue, we prefer not to have recommendations with asterisks. For this reason, we have not specifically endorsed the 13mm Ethos for Bino-Vue use because of the 63.5-mm diameter barrel (=63.5-mm interpupilary distance). Even so, we were advised by Mike Harvey at the Winter Star Party (2008) that only 1-person in 25 had interpupilary limits with the bino'd Ethos.

However, since many of our customers have been thrilled with the experience, we have maximized the potential use by narrowing the barrel from 63.5-mm to 62-mm diameter for eyepieces delivered beginning mid-March 2008. While the difference is only 1.5-mm, (or 0.75-mm for pairing a first production unit with current production) we decided to make this small change public, in case you want to give it a try.

Following are some of Mike Harvey’s Winter Star Party Ethos experience comments posted on Cloudy Nights’ Eyepiece Forum.

Read Reviews

After showing Ethos at a number of events since April 2007, we can safely conclude it brings the observing experience to a new level. This is based solely on user's reactions to views of familiar objects, not on any prejudgments, publicity or hype on our part. While we were quite confident of success, we wanted, and still want, to explore all the ramifications of what a sharp 100° field really represents.

Right after NEAF in April, Rodger Gordon, the acknowledged "eyepiece junkie" of all time, wrote me "Definitely the finest wide-angle eyepiece I've ever seen. If God is an astronomer, this is the wide-angle eyepiece he'd choose. You can quote me." Thanks, Rodger. I waited until now to avoid "priming the pump", so to speak before quoting your unbridled enthusiasm publicly.

For some time, I've been pondering just why the response has been so overwhelmingly positive. And if I really understand why, is it possible to quantify? My views of the Double Cluster at Stellafane pointed the way.

The 1991 article I wrote for Sky and Telescope on magnification provides the key. A major conclusion for low power states: "The best view occurs with the highest power that comfortably includes the target object. Higher powers darken the background sky, reveal fainter stars and show more detail. The resulting smaller exit pupil also minimizes the effects of eyesight defects."

Considering the potential of Ethos, let me posit a more general conclusion:

It's clear that the largest possible apparent field for a given true field yields the most magnification for greater resolution, with a darker sky background for more contrast as a result of the smaller exit pupil. I believe this combination of contrast, power and field causes the typical "wow" reaction — the Majesty Factor. I think Tom Trusock said it most succinctly in his Starfest (Canada) report: "The same true field at higher magnification means that you'll see blacker skies and more detail." Dennis di Cicco in his 5-star review of Ethos in his October 2007 Sky & Telescope review noted something similar: "Observing with the 12-inch scope, I typically bounce between a wide-field eyepiece for star-hopping and a high-power one for detailed views. But the Ethos gave me both. The field was large enough to star-hop, and the magnification was high enough to bring out faint stars and resolve details in galaxies and star clusters." (He coincidently also illustrated field sizes using the Double Cluster.)

Let's try to quantify the so-called Majesty Factor. While we cannot quantify the majesty of a great symphony, work of art or edifice, I think a meaningful Majesty Factor is quantifiable for those great deep sky views. Here's how:

Let's consider a range of possible eyepieces with apparent fields of 50°, 60°, 68°, 82° and 100°. Now let's pick an object, (like the Double Cluster) and let's say it's properly framed in the field of a 50° Plössl with a 26-mm focal length in an f/4 telescope so the exit pupil = 6.5-mm. Let's arbitrarily assign a factor of 1 to the power (magnification) of this telescope and a factor of 1 to represent the contrast for the 6.5-mm exit pupil. Therefore, for the given true field, the
Majesty Factor = 1 (power factor) x 1 (contrast factor) = 1.  

Now let's replace the Plössl with a 100° (apparent field) Ethos with a 13-mm focal length. This yields the same true field of view at twice the power with twice the apparent field and half the exit pupil. The 3.2-mm exit pupil is only ¼ the area of 6.5-mm, so the sky background darkens by a factor of 4 (contrast factor). The magnification power factor yields twice the detail or resolution. Therefore:
2 (power factor) x 4 (contrast factor)  = 8x Majesty Factor

Working out the math for all the apparent fields listed above, we have:

A simple rule of thumb is that for any two eyepieces having the same true field of view, the Majesty Factor equals the cube of their apparent field ratios. Example is (100°/70°)³=2.92.

  — Al Nagler

The Ethos has now been shown at NEAF, TSP, RTMC, and EPOCH 2007. We thought you’d enjoy sharing in the experience by reading some of the comments written in our “comment” notebook. The following display was created for daytime observation using the Ethos in an NP127is at NEAF and TSP, and an NP101 at RTMC.

The left chart has circles representing field diameters of 50°, 60°, 68°, 82° and 100° with the telescope distance set so that the 100° circle matched the view of the Ethos field-stop. The “crosshairs” are actually small Saturn drawings in 5° increments to illustrate the linear angular-magnification correction. Illustrations of Saturn were placed at the center and edge of the field so contrast and detail (including newsprint dot patterns) could be evaluated.

The chart to the right is an artificial very-rich “star field” made (and conceived) by Rick Scheck in our scope production dept. The bright “star” reflections made a more realistic contrast simulation than simply viewing astronomical pictures and helped to give a “night sky” impression that nicely represented a dense Milky Way star field.

Real night-sky viewing was done two nights at the dark Prude Ranch location of the Texas Star Party using telescopes ranging from our NP127is to the prize winning 12” f/5.5 Newtonian of our own Scott Ewart. Ethos also made its way into various large Dobsonians including those of Barbara Wilson and Larry Mitchell.

At the Riverside Telescope Makers Convention in California, we had two clear, though very bright moonlit nights for evaluation. Using an NP101 and NP127is Ethos treated us to clusters such as M44 and M24.

At EPOCH 2007 in western Indiana, we were pleased to have one very clear evening to demonstrate Ethos with our NP127is and Chris Brownewell's 25" Obsession. Good Luck, Chris, on this new star party venture, and a big Thanx for being a great host.

While all of us at Tele Vue are proud and excited by the response, it’s much more interesting for you to note the recorded comments. On a personal note, I was especially moved by just showing a random star field to a little 10-year-old girl in a group visiting RTMC from Anaheim. Her only words: “Oh my god, it’s beautiful.” It doesn’t get any better than that.

— Al Nagler

Kudos to our Paul Dellechiaie, the principal designer of Ethos.

NEAF 2007 Comments

• Wow! What a view! Clear right to the very edge. - C.M.
• Absolutely the best wide angle eyepiece I’ve ever seen - the 100° FOV. - R.W.G.
• The star field was “a religious experience”! - M.S.M.
• Another winner. Unbelievably wide. - S.F.
• It’s so good it’s scary. - R.F.
• Space-walk plus. - D.S.

TSP 2007 Comments

• Incredible field - sharp. - L.G.
• Sharp as a tack from edge-to-edge. - J.E.
• Extraordinary field-of-view. - R.J.
• Amazing! Very usable field - better than I imagined it could be! - T.B.
• Enchanting. - J.H.
• I could see no edge distortion to the edge of the field anywhere. Very nice contrast. - M.P.
• Just need to add the helmet for the full spacewalk experience! - T.W.
• Totally immersive experience! Thanks for bringing products like this for us astronomers! - D.A.
• Terrific experience!! - J.C.
• Very impressive. - M.S.
• Wonderful!!! - C.C.
• Remarkable. - R.M.
• Great! The Ethos sets the bar even higher; advances the hobby yet again. Super! - A.D.
• Outstanding - can’t wait. - D.M.
• Oh my God that’s incredible. - J.R.
• Excellent additional real estate in the wide field of view. - D.C.
• Thanks for making astounding equipment! - T.K.
• Awesome view through the Ethos! - K.P.
• The 13mm Ethos is an eyepiece that you can get lost in. You feel as if you could almost look behind you. - R.T.
• Ethos is super and can’t wait! Thanks, you and Tele Vue are the best! - A.A.
• Really do appreciate the view. - B.A.
• Nice, keep it lightweight. - K.M.
• Excellent - beautiful under the stars in the refractor! Great with my 20” f/4 on the Coma Cluster and the heart of the Virgo Cluster - makes my wide field f/4 better at wide fields! - B.W.
• Awesome view! - R.C.
• Great. - M.F.
• Very impressive 13mm on 127. Can I buy the star field!! - J.R.
• Ethos eyepiece does impress and another example of Tele Vue excellence. - L.D.
• The new eyepiece is a very easy eyepiece to see from. Has good eye relief, and is very clear. Everyone should have one. - J.D.
• Amazing! Sharp to edge. Virtually a binoc view. - J.B.
• Incredible sharpness edge-to-edge! - R.L.
• Amazing eyepiece! M13 (wow). - J.L.
• Oh WOW! - J.P.
• Nice eyepiece. - J.A.
• You can almost see behind you, wonderful. - D.R.

RTMC 2007 Comments

• WOW you did it again. I like it. - D.D.
• WOW! Tele Vue Visionary at its best! - T.P.
• Wow dizzy. - P.B.
• Wow it’s so wide it’s hard to find the edge. - C.E.
• Aghaaa 100° a galactic experience. - E.M.
• Can’t believe the view. - M.C.
• That’s incredible! - E.E.
• Impressive!! - F.J.E.
• Very nice to edge. - T.C.S.
• The most perfect wide-field optics EVER! Wow! - G.C.
• Oh my goodness! - K.K.
• Once again Amazing! I want one! - G.
• Love at 1st light. Very nice. Keep it up. - G.S.
• Wow! That’s amazing!
• Killer!!! I Need one! - R.L.
• What a view! - L.K.
• Rather amazing! - J.M.
• That’s a great view, sharp all the way across!
• Incredible. - R.G.
• Goodness Gracious. - T.D.
• Very good, very good, I love it. - M.
• Great! - J.S.
• Fantastic wide field. I almost have to imagine the field stop! And can’t wait to try one in both my TV-140’s.! - E.S.
• When you look thru this piece be careful not to fall onto the view?! Breathtaking. - S.S.
• It’s amazing. - J.L.
• It’s like a porthole to space. - G.N.
• After reading reviews waiting to get a close-up look I was blown away with the eyepiece. Sign me up I want one!! I was inside the telescope reaching out to touch the stars. Amazing!!! - G.W.
• 100° WOW I love it! - S.A.

EPOCH 2007 Comments

• Large Field! Wow! Great to have the magnification and the wide field. Best of both worlds. Eyegasm! - Chip (16" Lightbridge)
• Be prepared to look around! The Ethos was lighter than I thought it might be and there was no coma at all in my 20" f/5 Obsession. M-27 was fantastic as was M-13. Viewing the double-cluster thru a TEC 6" I felt like I needed someone to hold onto the back of my shirt so I wouldn't fall in! It's on my list to get! Thanks for the views Al. -- M.M.
• Fantastic - wow - a real winner! Very undistorted. Thanks Al. -- F.H.
• Spectacular! Beautiful eyepiece, very comfortable to look through. Thank you for bringing Tele Vue to Indiana. -- A.M.
• Super Wide Field - Excellent. -- anon.
• 13mm Ethos - Awesome F.O.V.! Almost too much to take in at once. Can't wait to get one! -- D.H.
• Wow! Wow! -- J.M.
• Sweet! Great View. -- R.M.
• Once again - as usual - we can offer perfection to our discriminating customers -- thanks to Al Nagler for making it fun to be a telescope dealer. -- W.M.
• Just didn't think a "31" could be one-upped. I was wrong!! Incredible!! -- anon.
• Super Wide Field Ethos eyepiece: Lagoon nebula had clarity of stars edge-to-edge in view. All stars "tack" sharp. M13 was as if I'd never seen it before. Outstanding. -- J.M.
• Super wide field - unbelievably exceptional / outstanding view; crisp, clear -- wow!! Don't think I've seen anything that great until now. -- S.
• The field-of-view is so extensive that I had to almost crawl inside to look at it all. -- C.D.
• Looking through Ethos 13mm gave me the same exciting feeling I got looking through a Nagler the first time. Same WOW factor. Can't wait for high power Ethos. -- B.C.

Stellafane 2007 Comments courtesy Dave Mitsky

• The two most memorable sights of the night for me were both through Tele Vue's incredible 100 degree AFOV 13mm Ethos ocular. M27 through John Vogt's 32" ATM Dob and the Ethos was truly unbelievable and I've never before seen M31 as mind-blowingly extended as I did through Al Nagler's 127mm Tele Vue apochromat and the Ethos. This yet-to-be released new eyepiece is simply amazing. -- Dave Mitsky, A Brief Report from Stellafane 2007, bautforum.com

Starfest (Canada) 2007 Comments courtesy Tom Trusock

• [B]lew me out of the water. We used it on the NP101 and a 20" f5 obsession - to spectacular results with both. This eyepiece takes the Nagler philosophy to the next level - The same true field at higher magnification means that you'll see blacker skies and more detail. So, although it's extremely impressive, the massive sense of immersion could almost be considered a secondary effect.
  But what a secondary effect.
  For me, the most striking view this weekend was of M31/32/110 in the NP101 - simply amazing. On this scope, the eyepiece generates about 40x, and nearly a 2 and 1/2 degree field! It was really funny to see a line of up to 20 people in front of this little 4" telescope, and the huge 20" f5 right next to it sitting totally empty. This was definitely one night where aperture didn't win.
  The Ethos is truly the next revolution in visual astronomy.

  -- Tom Trusock, First Light - Ethos, cloudynights.com - eyepiece forum

“Distortion becomes especially important in wide-field eyepieces.  In discussing distortion, however, one must clearly distinguish between rectilinear distortion and angular magnification distortion.  For terrestrial telescopes, it is often required that straight lines in the focal surface look straight in the eyepiece.  For zero rectilinear distortion, the following relationship should apply:

y  =  f  ∙ tan ß

where y is the off-axis distance in the focal plane, ß the image angle from the optical axis, and f the focal length of the eyepiece.

For astronomical observation, however, it is important that the angular magnification remains constant over the field.  For instance, the angular distance between double stars should be the same and a round object (a planet) should retain its shape whether viewed in the center of the field or at the edge of the field.  In this case, the following relationship should apply:

y  =  f  ∙ ß

where ß is expressed in radians.

With zero angular magnification distortion, straight lines on a focal plane appear curved in a pincushion fashion, with the curvature becoming greater the farther they lie from the center.  It is impossible to correct an eyepiece simultaneously for rectilinear and angular magnification distortion.”

Al Nagler notes:

For reference, the maximum angular magnification distortion of the new 13mm Ethos is no more than 1% at any point in the 100˚ field

Eyepiece Accessories
EBX-2120			2” Eyepiece Barrel Ext.

Ethos

Type	Model #	Focal Length (mm)	Barrel Size (in.)	# Elements / # Groups	Apparent Field of View (deg.)	Parfocal Group	Eye Relief (mm)	Weight (lb / oz)	Image
Ethos	ETH-21.0	21	2"	/	100		15	2.25 / 36.0
Ethos	ETH-17.0	17	2"	/	100		15	1.55 / 24.8
Ethos	ETH-13.0	13	2" & 1¼"	/	100		15	1.30 / 20.8
Ethos	ETH-10.0	10	2" & 1¼"	/	100		15	1.10 / 17.6
Ethos	ETH-08.0	8	2" & 1¼"	/	100		15	0.95 / 15.2
Ethos	ETH-06.0	6	2" & 1¼"	/	100		15	0.97 / 15.5
Ethos	ETH-03.7	3.7	2" & 1¼"	/	110		15	1.10 / 17.6

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