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Usage strategy: Eye patch / sleep masks for happy, extended, one-eye spotter viewing. (1 Viewer)


Well-known member
Hello Everyone,

I love spotting scopes, and the incredible detail they deliver. But, I most certainly dislike viewing through the scope with one eye while shutting the other. I find it to cause great strain in both my eyes significantly limiting (a) observation time, and (b) as I would later confirm with a suggested solution below, potentially interfere with stable eye-positioning over the scope.

Although problem (b) is very minimal with our relatively narrow FoVied Kowa663M + TE-9Z scope, I still could distinctly recall how the 20-50X Wide angle ATS eyepiece from Swarovski left me totally bewildered with the kidney beaning effects partly because I couldn’t keep my head steady!

A simple thought occurred: Why not let a sleep mask (or an eye patch) go over the unused eye? And, look through the scope with one eye still, but leave the other eye open as it would be “normally”? I later found out online on other forums (but somehow not ours?) that this is a common strategy used by many other spotter enthusiasts who dislike one eyed viewing for eyestrain or other reasons.

I tried it in the field, and what a difference!!!! Zero eyestrain whatsoever. No problem “glass”-ing however long, panning through the shorebird varieties filling the landscape from one end to the other, IDing them one after the other creating a LIST(!), all the while not taking the eye off the eyepiece one bit! And during that entire time, I would find that I had no reason to reposition my eye for any stable eye positioning -- other than accommodating the eye-cups for any zoom-related eye relief change!

Of course, the sleep mask comes off/stowed away after observation, depending on one’s preference.

I thought I would share this experience, suggest to anyone curious, and welcome your thoughts on any other alternative strategies that people have found over the years.

If you do try it out / have tried it out, it would be great to hear about your experience as well.

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Well-known member
I have done this when needed for well over fifty years.

As an astronomer I trained myself from age 15 to keep both eyes open and ignore the view in the other eye.

Periodically, I would also refocus as this can change with extended viewing.

I would also swop eyes, as both worked well with a telescope.

So either an eye patch from the chemist/drugstore? or I keep both eyes open.
I don't observe for long periods now as my eyes get tired.

I also kept both eyes open when rifle shooting as a cadet.
We used a 20x or maybe 22x spotter to see the .303 holes at 300 yards, although a 10x would have probably shown them also.



Well-known member
That's interesting @Binastro that you are able to observe with both eyes open. I am going to give it a go as well!


Well-known member
It takes a lot of practice to keep both eyes open, and maybe best done as a youngster.
One has to be relaxed doing this with no strain.

We get set in our ways as we get older.



Well-known member

I used a patch at the start too but have learned to observe with both eyes open... it helps if there is nothing to see with the other eye because the stay-on case is blocking the view...



Well-known member
Started to use my scope with both eyes open when my shut eye became increasingly blurry after long periods of watching. My mate had done it for years and used to ridicule me for being ‘a one eyed loser’, and some bloke called Anthony McGeehan recommended it in a book too... Sometimes I struggle, especially when it’s bright and I’m looking at something miles away. Other times, it’s seamless and I forget I’m even doing it. I pull the fabric lens cover over to the side of my closed eye. It’s dark coloured and helps dull the image that my brain is trying to ignore.


Forum member
Hi Henry,

Within this thread on the Swarovski BTX binoviewer there is a side discussion about keeping both eyes open when viewing through spotting scopes, including some ideas about ways to blacken the view of the unused eye. It starts on page 3, post #75 and continues through post #101.

Thanks a lot, quite interesting!

The forum engine allows direct links to specific posts, by the way:





Well-known member
Binastro I like the 303 bit.

I happened to give a No4 to my younger brother for his 15th birthday and we shot it quite a bit in our youth. (Maybe I was a bit selfish on that gift). You're right you have to learn earlier on to one one eye when sighting. Here you cant close or squint the left eye as it would affect your sight picture. You have to relax your eye just right as well....

Later on in matches we also learned to use both eyes...The Right for the irons on the rifle and the left to look in the spotter. The 20x spotters were mostly from the previous generation but in my time the 25x and Especially 25xLER from Kowa was the norm.

I would suggest maybe a little practice with keeping an eye open...A patch might feel a little distracting?

You could seek out a pair of knoblochs with a blinder. If you wear glasses you can use a prescription diopter as well as the blinder.


Well-known member
I had the same issue but solved it with a pair of 70mm 45degree Astro binoculars (APM and Oberwerk make suitable ones), take wide range of eyepieces. Now I have ultrawide, crisp views at 30x (more when I’ve saved for some shorter eyepieces). Could add some side shields to reduce straylight if needed. About the same weight as the BTX, but cheaper.



Well-known member
That's interesting @Binastro that you are able to observe with both eyes open. I am going to give it a go as well!

For me it is all about the size of the eye lens I have to look thru. The larger the lens, the easier it is to relax and use two eyes. With my Nikon EDG 65 Scope the 25x wide eyepiece(shown on scope) is so big, using two eyes is very easy to view thru.


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