Televue Ethos Eye Problem

[Profiler (Profiler)]

I am hoping someone might have some knowledge/answers to share with me about a problem I encountered with a Televue 13mm Ethos

Last night I was looking at the planets with a variety of eye-ball crushing plossls and orthos which have little eye-relief. So, basically for about 2 hours I was using a variety of the supposedly uncomfortable but optically sharp eyepieces which respectively had anywhere between 6-10mm of ER and about a 40-50' degree fov. I was viewing for about 2 hours and felt nothing (ie perfectly fine - not even tired).

Then to conclude the night I thought I might do a little widefield observing for about 10-15 minutes and put in a 13mm Ethos. The view was fantastic!! The eyepiece lives up to its reputation and I loved it. HOWEVER, within 5 minutes my eye actually started to ache and felt sore from looking through the eyepiece. I couldn't believe it as the Ethos is much more comfortable with 15mm of ER but I couldn't help but suspect something to do with the 100' fov might account for this circumstance. My eye actually started to hurt and I had to stop.

As I type this post the following morning my eye still feels ever so mildly sore from looking through the eyepiece as if I have something stuck in the bottom of my eye.

So - can anyone suggest or tell me what I might be experiencing? I love the 13mm Ethos and the product is wonderful but why is my eye hurting from using it? especially when I am fine when using the supposedly eye-straining short fl orthos/plossls

[Don Pensack]

Since I've never experienced what you experienced with any eyepiece, I can only speculate:
--the much wider field meant you were constantly shifting your gaze from here to there all over the place, rather than keeping your eye pointed straight ahead.
--you were so enthralled at the image you forgot to blink. And the after effects of a dry eye are bothering you.

You might try rolling your head over a bit to look at the edges of the field to keep your eye from straining sideways that much. After all, that's what you normally do--when you want to look left, you don't hold your head still and move your eyes, you move your head and look left.

But there is nothing inherent in the eyepiece that would lead to any symptoms such as described, so I'm guessing my explanation is probably correct.

[Profiler (Profiler)]

Originally Posted by Don Pensack

Since I've never experienced what you experienced with any eyepiece, I can only speculate:
--the much wider field meant you were constantly shifting your gaze from here to there all over the place, rather than keeping your eye pointed straight ahead.
--you were so enthralled at the image you forgot to blink. And the after effects of a dry eye are bothering you.

You might try rolling your head over a bit to look at the edges of the field to keep your eye from straining sideways that much. After all, that's what you normally do--when you want to look left, you don't hold your head still and move your eyes, you move your head and look left.

But there is nothing inherent in the eyepiece that would lead to any symptoms such as described, so I'm guessing my explanation is probably correct.

Hi Don

First - I want to clarify that at no point in my original post did I even suggest there was any sort of fault with the eyepiece. This is something to do with me, my eye and the reason I am making these inquiries is, quite the opposite to being unhappy with the Ethos, I do in fact very much want to keep it and need to figure out how to go about this without my eye ache.

Now, a little back-story which I am wondering might be the easy answer. This is not the first time I have looked through an Ethos eyepiece. Interestingly, what I am now experiencing with my eye I previously felt about a year ago when I tried looking through the 21mm Ethos. Because it hurt my eye I didn't like the 21mm Ethos. At the same time I also looked through the 13mm Ethos and didn't feel this pain or at least ddn't notice anything like what I am currently experience. Hence why I wanted the 13mm Ethos

HOWEVER, the 13mm Ethos which I previously looked through was fitted with a Televue eye-guard extender. Consequently, I am wondering whether with the extender fitted to the Ethos my eye is placed at a suitable distance away wherein I am not incurring the eye-strain? I really hope this might be a simple answer to my problem in buying an extender

[ab1963 (Andrew)]

Originally Posted by Don Pensack

Since I've never experienced what you experienced with any eyepiece, I can only speculate:
--the much wider field meant you were constantly shifting your gaze from here to there all over the place, rather than keeping your eye pointed straight ahead.
--you were so enthralled at the image you forgot to blink. And the after effects of a dry eye are bothering you.

You might try rolling your head over a bit to look at the edges of the field to keep your eye from straining sideways that much. After all, that's what you normally do--when you want to look left, you don't hold your head still and move your eyes, you move your head and look left.

But there is nothing inherent in the eyepiece that would lead to any symptoms such as described, so I'm guessing my explanation is probably correct.

This sounds to me like a very logical answer to this issue

[N1 (Mirko)]

Hi Profiler, if you check closely the area between your eyeball and the skin you might find the 6mm Ortho is still in there somewhere. The 4mm ortho can sometimes travel down the tear duct and be retrieved by blowing your nose

Joking aside, while I have not experienced any actual after effects of looking through wide angle EPs, I have noticed that for my eyes at least there is an inverse correlation between AFOV and viewing comfort if the eye relief stays the same or roughly the same. Or viewed from a different angle, ER must increase with AFOV if viewing comfort is to be similar. The 12mm of ER on my 13T6 "feels" about the same as the sub-5mm ER on my 6mm OR. I put that down to the fact that a wider AFOV means a wider eyelens and a wider eyelens often means a wider body. Things like eyeguards or recessed eyelenses complicate matters further. A clean, flat top on a body not much wider than the barrel can go a long way in making viewing more comfortable.

[Don Pensack]

Well, it seems that the eyepiece must have too long an eye relief for the length of the eyecup.
On short eye relief eyepieces, the eyecup is long enough for you to "bury" your eye in the eyecup and be at the right distance from the eyepiece.
This is not true, however, for the Ethos. One must hold one's head a bit away from the eyecup in order to be at the right distance and not experience blackouts (which could, indeed, make using the eyepiece uncomfortable).
First, use the eyepiece with the eyecup folded UP. This will automatically force your eye a bit back from the eyepiece.
Second, approach the eyepiece from a distance and stop whenever your peripheral vision catches a glimpse of the field stop of the eyepiece. At that distance, your nose may touch the eyecup, but the rest of your eye socket will not. If you have trouble holding your head at that distance (and I presume you are sitting, since standing is not stable enough to hold the eye away from the eyepiece), you could try the Eyeguard Extender, but be aware that it will sacrifice almost half of the eyepiece's eye relief.

TeleVue must be aware of this phenomenon, since the newer Delos and Delites have eyecups that raise up to a height where people who are so inclined can truly insert their eyes into the eyecup to see the whole field of view.