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Televue Ethos 13mm with Pentax PF100ED (1 Viewer)

Can Popper

Can Popper

Well-known member
Well, my Televue Ethos eyepiece finally came in and I decided to try it with my Pentax 100 spotter.

Sadly, the 2" shroud on the Ethos is preventing the eyepiece from seating fully into the scope. As a result, the scope/Ethos combo won't come to focus beyond 30ft. I took apart the Ethos to see if the shroud was removable but alas, it seems to be the middle part of the eyepiece. There was an aspheric lens inside the shroud. The 1.25" smyth lens attaches to it and it to the upper part of the eyepiece.

I'm going to contact Televue to see if they offer a replacement part that doesn't have the 2" shroud. If they don't, I'll probably contact Harry Siebert to see if he can machine me one and move the aspheric lens into it. Hopefully that will allow the Ethos to come to focus at infinite.

As you can see from the attached picture, the Ethos is one big eyepiece. About the same size as my Pentax SMC zoom.
 

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I'm curious "Can", what got you barking up that tree? I understand the allure of a 100 degree AFOV, but have you tried a Nagler on your scope yet? I tried several type 6s on my PF80ED and didn't much like them. Quite noticeable distortion (and CA) for terrestrial viewing and I am assuming the Ethos will have more yet. For deep sky astro use they are wonderful, no doubt, but I am skeptical of their merit for nature observing.
 
I decided to bark up the Ethos tree because I Can ;)

The reviews of the Ethos I read said it was much superior to the Nagler so I figured why not?

From what I saw today, I didn't see much distortion nor CA. Of course I couldn't see beyond 30 feet either...LOL. It seemed to be a good eyepiece if I can just seat it deep enough.
 
Ok, I first called Televue and Al Nagler of all people picked up. LOL

I asked him if there was a way to remove the 2" eyepiece shroud and he said no, the eyepiece was designed that way. He told me I could get a machinist to cut the shroud off if I didn't plan to resell.

So I called up Harry Siebert next. Harry said it would only cost me $30 to machine the shroud off so I'll be shipping my Ethos to him soon.
 
Yep, I've talked to to Al on the phone before as well. Pretty cool eh?

Clearly you are serious about using the Ethos on your spotting scope, to (essentially) make it unsalable. I hope it works out well and you like it. I look forward to reading your report!

Added: Just a precaution, you did measure the depth from the collet of the scope to the glass window and compared that with the available depth the EP will have with the 2" ring cut off, correct? You are confident the scope will attain infinity focus after this mod?
 
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One never knows until one tries 8-P

I'm pretty confident though. I had eyepieces that wouldn't come to infinity focus when fully seated inside (Siebert Ultra 9mm). The fact that the Ethos can come to focus to 30ft when seated 3/4" high is rather promising.

Worse come to worse, I'll end up with a standard 1.25" eyepiece. Or I can reorder that middle shroud part to restore it back to normal. It is only one part out of 3 that is being modded.

Gods of Knowledge and Spotters, I bring you this Televue Ethos as sacrifice. If it pleases you, please grant me an awesome spotting scope eyepiece and bragging rights when all is said and done.
 
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Well if it doesn't work for you I'd be willing to buy the ethos from you with the 2inch part cut off. Good luck keep us posted.
 
Another alternative would be to take the barlow element from a shorty barlow and screw this into the eyepiece, and then use the eyepiece. I have successfully employed this method with eyepieces that would not on their own come to focus in my diy spotter. The only disadvantages are increased magnification (may be an advantage) and more glass in the optical path.

Rmel66.
 
Ok, I got my Ethos back from Harry Siebert. The machining off the shroud turned out to be fairly easy and he only charged me $30. As you can see from the pictures, he did a fine job. My Ethos now looks like an Orion Stratus with the hybrid 1.25" and 2" portions as you can see below.

Unfortunately, the machining off the shroud increased my focus range from 30ft to only 170 yards. I managed to extend the focus range to infinity by screwing on a Siebert 1.6x OCA into the eyepiece's nose.

The image quality with the OCA is still very good as you can see from the before and after pictures. I compared the image with the OCA with my 10mm Pentax XW eyepiece and the Ethos has better image quality and a bit less magnification. The OCA does make the Ethos into more of a 12mm eyepiece compared to its original 13mm.
 

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Can Popper said:
Unfortunately, the machining off the shroud increased my focus range from 30ft to only 170 yards. I managed to extend the focus range to infinity by screwing on a Siebert 1.6x OCA into the eyepiece's nose.
Click to expand...

Bummer. Though the Siebert OCA makes it usable, I'm sure you'd prefer not to use it. I'm a little surprised you don't have clearance issues with the OCA attached.
 
Can,
Thanks for sharing your tests. I was waiting for a Ethos 5mm to replace my XW 5 mm - the Nagler 5mm has too reduced eye-relief for me, since I use glasses. Meanwhile, with the focus issues you detected I might go for the baader zoom and the barlow 1.6x http://www.birdforum.net/showthread.php?t=152519 - at maximum zoom it has the same field of the XW (as also a "window" view), and at the lower power it has higher field of view than a 5mm Ethos would have, since is 80% more than at maximum power (as also of the XW5).
If the crop factor is the same in both your photos, the increase of magnification should be higher than you estimated - use the "roof panels technique" to estimate the increase of power...;)

David
 
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