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Review of Zen-Ray ED2 82mm Scope (2 Viewers)

I see that FrankD has revealed that Zen-Ray is about to announce a 25-50x wide angle zoom. I tested a prototype, but unfortunately I don't have much time to write about it now. I'll say that that I was surprised to see a healthy dose of barrel distortion at the low magnification end, something I don't think I've seen in an eyepiece before. Also, unlike most zoom eyepieces the eye relief is shortest at the lowest magnification. I'll see if I can find my notes and write a little more tomorrow.
 
Henry,

Charles gave me the go-ahead to mention it a day or two ago which is why I posted about it. I thought you might have more to say on it than I at this point.

I was surprised to see the same thing you did with the barrel distortion. I picked it up when panning with the scope. Stationary I did not notice it as much. At 50x it is greatly reduced and I just cannot believe how sharp and bright the image is at the 50x setting. Impressive!
 
Here are some measurements of the AFOV and eye relief of the Zen 25-50x prototype. Keep in mind that the final production version may be different.

AFOV is the "true" apparent field including distortion. In this case that causes a somewhat smaller apparent field than expected at low magnification because the distortion is barrel rather than pincushion. Eye relief is measured from the rim of the eyecup. It would be about 4mm longer measured from the glass of the eye lens.

25x AFOV - 54 degrees ER - 10mm
30x 60 degrees 11mm
40x 65 degrees 13mm
50x 68 degrees 14mm

If you compare these numbers to the 20-60x you find that the eye relief of the 25-50x is shorter at magnifications up to about 35x, but longer between 35x and 50x. I should also mention that the rubber eyecup design of the 20-60x has a 6mm recess instead of 4mm, so the difference in optical eye relief is 2mm more in favor of the 20-60x than my measurements from the rim.

I compared the 25-50x zoom set at 30x to the 30xw eyepiece. The zoom had a slightly wider apparent field and much better off axis sharpness. Longer eye relief was the only advantage I could see for the fixed magnification 30x.

I agree with Frank that the zoom is bright and sharp at the 50x setting, in fact brighter and sharper than the Zen scope allows you to see. I didn't find it to be any better than the 20-60x set at 50x. Neither compromises the scope's performance. It's the scope that compromises the eyepieces.

I also briefly compared the Zen zoom to a Swarovski 25-50x zoom in a store. There were similarities in the reflection patterns, but there also appeared to be some differences and some optical characteristics were clearly different. The Swaro does not have barrel distortion and its eye relief is longer. Perhaps because of the short eye relief the Zen does not display the tendency to blackouts that I notice in the Swarovski.

If I were buying the Zen ED2 scope I would probably choose the 20-60x just for the extra detail visible at 60x. If you are inclined toward a 25-50x wide field zoom this is an impressive eyepiece, with a couple of caveats. If you wear eyeglasses the eye relief may be too short to take full advantage of the field and some people are going to experience "rolling ball" when panning because of the barrel distortion.
 
"I agree with Frank that the zoom is bright and sharp at the 50x setting, in fact brighter and sharper than the Zen scope allows you to see. I didn't find it to be any better than the 20-60x set at 50x. Neither compromises the scope's performance. It's the scope that compromises the eyepieces."

Henry Link,post 23,paragraph 6#

Hi there...I got the Swarovski 30XWA today..It is the older version,without a locking pin retainer,and does fit the ZEN bayonet perfectly.The fit is secure and tight.It is a small,lightweight eyepiece too,a bit taller that the Zen 30X but not larger ...The eyepiece JUST ..I mean..I fell in love instantly..beautiful ,amazing,you name it...
the 20-60X Zoom might be a superb eyepiece,but in my opinion,after today´s brief observation, does Not bring everything the scope is capable to the table,neither does the ZEN 30X,..The improvement is SO evident that there is no need to side by side comparing the views,..I can clearly tell that the zoom @ 30X doesn´t show this kind of detail..plus the image snaps in focus positively...The Swarovski 30XWA view is about as wide as the Zen 30X,but with better edge performance,and better performance in every other regard,including CA..Within the distortion free area of the image,probably about an 85% ,that is already sharp,there is a central Sweet spot,not huge,but large enough,and very, very SHARP..crispness..detail...texture..contrast...All there..

I love it..I catched a kestrel flying far,far ,far away ,while viewing from my roof ,and the view and detail impressed me, got me excited about the scope, and in other words,Convinced Me!...
I must say that ,using the ZEN eyepieces, I was happy with the view ,but not impressed to the WOW factor..today I WOWED!..
So at the moment I disagree with Henry Link in His view ..I see that the limiting factor ,in my unit at least ,was the eyepiece....It was good ,but today ,with a different eyepiece(an exceptional one)the scope showed exceptional performance.
 
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mayoayo,

I should probably allow you to get past the WOW state before I even agree that we disagree.

As you might guess I would prefer to read the results of a controlled test rather than an impression. A line pair chart to quantify the smallest visible details would be good and, even better, a booster scope placed behind the eyepieces to magnify any degradation of the 30x image caused by one or another of them. It really would take a very poor or defective eyepiece to limit the axial detail visible in this scope at any magnification, so once you've recovered from being WOWed by your new eyepiece, maybe you could do a more methodical test to determine whether your Zen eyepieces are really that bad.

Henry
 
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Henry..I will try to back up my impressions with some quantifiable data,like pictures of fine printed text or something like that..Visually ,I had hints of the Swaro-Zen combo performing a bit better in terms of resolution,than the ZEN 20x60 combo,but to be honest there is not fine print or distant license plates(my resolution charts!)that I have been able to read with the Swaro 30X that I wasnt able to discern as clearly with the Zen Zoom..Yet,there is a more detailed description of texture in the image,and I can more easily attain sharp focus while using the 30XWA swarovski..
 
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Pictures

I took a couple of photos,using the ZEN scope and both eyepieces,the 30XWA Swarovski (old version) and the Zen zoom at 30X...
I used same camera settings and the best focus I could achieve through my cam screen on such tiny print...the subject is a pack of "EMERGEN-C" at 25 feet . The size of the whole detail is 1 inch long,so you can get the idea of the size of the letters ..camera is a Canon A590IS ,zoomed one touch(still vignetted a bit in the zoom.).image is cropped to real size,untouched otherwise,light is identical in both shots,pictures taken 1 minute apart.Photo One taken with the 30XWA
 

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Impressive review henry, theres a lot of information to process....like the unit you tested sometimes myne do show that back and forth search of focus at 60x, but I allways related that with mirage, in fact that happens alot more with bright hot mediterranean days.
But probably its me being picky, because I want the image at 60x to be as good as the view at 20x ...... sometimes it allmost is, and I find myself turning the zoom for more mags just to realize that I am using 60x already.
Nice to know about the new Zen wide angle zoom, but it would be nicer to hear about a new high power one, like a 75x.

Since some eyepieces do fit the Zen body, would the new swarovski astro adapter be an option? http://www.juelich-bonn.com/site/spektiv/swarovski/z43/astroadapter.html
 
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Manuel,

Interesting comparison between those two eyepieces. Assuming you have achieved sharp focus in both eyepieces it seems as if the Swarovski has better contrast (the letters seem blacker) but with some CA present (black lines above "Supplement" and below "Serving size"). I see noticeably less in the Zen Ray pic. Subsequently the letters seem slightly more defined though I don't know if I would say it is any "sharper".
 
Manuel,

I don't think these photos should be relied on. If I believed that what I see in the photos was actually coming from the different eyepieces I would say that the eyepiece on the left is inferior to the one on the right. On my computer screen its image is darker, less sharp and shows more lateral CA, but I suspect those are more probably photo artifacts, perhaps a little better focus in the right photo, maybe a little misalignment of the camera lens with the eyepiece in the left photo. I confess I've never succeeded in digiscoping images through any telescope that contained as much detail as my eye could see through the same scope. I'm sure it can be done with the right equipment and techniques, which would have to include a long enough lens on the camera to magnify the scope image sufficiently so that the smallest details in the scope are comfortably larger than the camera pixels. Then very precise focusing and alignment of the camera to the scope would be needed and of course complete freedom from shutter vibration.

Rui,

Telescopes with low aberrations are actually a bit more resistant to "mirage". That's based on the principle of addition of defects. The overall image of a scope gets worse as defects are added together, so spherical aberration + air turbulence looks worse than air turbulence without spherical aberration. I've seen this many times when comparing low aberration telescopes to higher aberration scopes.

I think there's a good probability that the Swarovski type astro adapter will work on the Zen scope

Henry
 
Yes ,the pictures dont say a thing,I agree...I sat the camera on a table,and placed the scope in front of it ,at the right distance,then used the timer..but the setting was definitely too dark,and the camera shutter not fast enough,so artifacts are showing...
I am now looking for a 6mp DSLR ,with large pixels and large sensor..probably a Pentax K100D,to couple it with an older M-50mm 1.7...extremely sharp wide open...this combo could give some results,and it is very cheap these days..
 
Unfortunately, big pixels make photographing the scope's resolution harder, not easier. That's the problem I have with the Nikon D40, which has huge pixels. Remember, the smallest resolvable details in the scope have to be larger than the pixels when their image is projected onto the camera sensor. That means the larger the pixels the the more the scope details have to be magnified, either by increasing the scope magnification or increasing the focal length of the camera lens.

To be sure you're photographing the true resolution you need to push the magnification until the smallest resolvable details are large enough to look blurry. If the photo looks nice and sharp it hasn't been magnified enough. That's why you can't tell much about scope performance from impressive looking sharp photos. Any scope will look good if the magnification is low enough for the resolvable details to be smaller than the pixels.
 
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Then I need a set of extension tubes to be able to make the scope focus at 8 or five feet..that would give a 3x or 4x boost to the size of the image in the camera sensor...Ill try and go that route...Thanks For all the information
 
Manuel,

Extension tubes between the scope eyepiece and the camera lens won't change the close focus or the magnification. In any case you wouldn't achieve anything by moving the target closer. That wouldn't change the relative size of the scope details and the camera pixels. The best you can do, since the scope magnification is set at 30x, is to zoom the camera lens to its maximum focal length to increase the magnification.

Henry
 
henry link said:
To be sure you're photographing the true resolution you need to push the magnification until the smallest resolvable details are large enough to look blurry. If the photo looks nice and sharp it hasn't been magnified enough. That's why you can't tell much about scope performance from impressive looking sharp photos. Any scope will look good if the magnification is low enough for the resolvable details to be smaller than the pixels.

To acomplish this, should we use a booster Henry? I have been using the maximum focal length of my compact camera (105mm), and I still cant capture on photo the true resolution of the scope at 60x.

Another question, I have been trying to film the star test, with my compact, but I can only capture with success the difraction rings on inside focus & outside focus when they are to enlarged, the rest of time the camera cant cope with the amount of light, I think....do you have any idea how to do it without compromise the star test results?

thanks in advance....
 
Henry....If I set the extension tubes between the scope and the eyepiece,the scope will focus closer...30X at 5 feet is larger than 30X at 20 feet....that is the whole concept behind macro photography....closer=bigger=more detail...
 
Manuel,

I didn't realize you were thinking of extension tubes between the scope body and the eyepiece. Are there are tubes that would fit? Even if they exist they won't have the effect you're expecting and will introduce profound changes in the scope optics.

Simply moving a target closer to the scope does not increase the scope's magnification. It's almost no different from examining a larger version of the target at the original distance. It's not quite the same because you have to increase the distance between the objective and eyepiece to reach focus, but that will have a relatively minor effect on the magnification of the scope. The infinity focus focal length of the Zen is 464mm. At 16' it has probably increased to maybe around 500mm. To focus to 5' would be probably require about a 125mm extension tube which would increase the effective focal length to around 625mm, so the increase in scope magnification compared to 16' would only be about 25%. But, this comes with an unwanted side effect. The prism is now way out of its optimum position in the light path, so it will probably stop down the aperture to less than 60mm. Zooming your camera lens to the maximum focal length will have a much bigger effect on the magnification without the side effects.

Henry
 
To acomplish this, should we use a booster Henry? I have been using the maximum focal length of my compact camera (105mm), and I still cant capture on photo the true resolution of the scope at 60x.

Another question, I have been trying to film the star test, with my compact, but I can only capture with success the difraction rings on inside focus & outside focus when they are to enlarged, the rest of time the camera cant cope with the amount of light, I think....do you have any idea how to do it without compromise the star test results?

thanks in advance....

Remember, I haven't been able to photograph the resolution either, so I'm not the best one to offer advice about how to succeed at it. My assumption is that I haven't used enough magnification.

As far as star test photos, I assume you mean that the camera is overexposing stars that are close to focus. I just use manual exposure with the camera lens wide open (you don't want it to be smaller than the exit pupil coming from the scope) and then keep trying different shutter speeds until I find one that works. The correct shutter speed increases as the diffraction disk shrinks.

Henry
 
Henry..moving the target closer doesnt change the scope magnification,but increases the size of the image at a given magnification...One of the big brands,dont remember which, makes macrotubes for their spotting scopes...
Yes ,the use of an extension tube would make the image very dark , the same downside effect than using SLR attachments
 
It isn't just that the image will be darker, the scope will change from an 82mm f/5.65 to a 60mm f/10.4. The eyepieces will no longer see the same shaped light cone so their behavior will change and you will be no closer to accurately photographing the image as you see it at 30x.
 
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