[mayoayo]

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..

[mayoayo]

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

[Rui_Caratão]

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/spe...roadapter.html

[FrankD]

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".

[henry link]

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

[mayoayo]

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..

[henry link]

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.

[mayoayo]

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

[henry link]

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

[Rui_Caratão]

Originally Posted by henry link

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....

[mayoayo]

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...

[henry link]

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

[henry link]

Originally Posted by Rui_Caratão

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

[mayoayo]

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

[henry link]

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.

[mayoayo]

Ill try again with my cam ,better light,and more time...I know that WB has to be right to get the artifacts under control,and i didnt do this with last pictures...I will try doing a custom reading of white balance before each shot,...focussing both eyepieces right is critical.maybe with better light I can do better.I will try another target too,flatter and not shinny

[Rui_Caratão]

Originally Posted by henry link

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.

I wasnt refering to photos henry, those I was more or less able to do with my compact digital camera (no manual function), the ones you comment on SteveC thread.
I was trying to do a small video of the star test, but like you said the camera probably is overexposing, and instead of 3 or 4 diffraction rings, theres only a hudge amount of white light.... when the camera copes with all that light the scope is to out of focus to see the center diffraction rings.
Anyway to decrease all that light without compromise the star test? What if I stopped down the Zen to 70mm or less.....

[henry link]

Yes, the problem is that no single exposure setting will work. A big out of focus pattern with lots of rings contains the very same amount of light as a tiny one with only a few rings, so the surface brightness is much higher for the small one.

You wouldn't want to stop down the scope. That wouldn't help the exposure problems since the small discs closer to focus would still be brighter than the big ones further from focus. It also wouldn't accurately portray the full aperture performance. In the case of the Zen scope a stop down would eliminate the impinging prism and clean up the aberrations.

Henry

[Rui_Caratão]

I see, henry...thanks for the explanation.

Originally Posted by henry link

It also wouldn't accurately portray the full aperture performance. In the case of the Zen scope a stop down would eliminate the impinging prism and clean up the aberrations.

I probably dont understand the all concept and the many variables envolved, but the way you put it, it sounds like a stopped down scope with SA could perform better than the same scope at full aperture.

[IvanCavallazzi]

Originally Posted by Rui_Caratão

I see, henry...thanks for the explanation.



I probably dont understand the all concept and the many variables envolved, but the way you put it, it sounds like a stopped down scope with SA could perform better than the same scope at full aperture.

It is possible to emulate the star. Sometimes I do casual star test in little singular points of reflection from the sun against things. And so the rest don´t need to be full black and maybe the evaluative exposure won´t be a problem. I never tested like that... but may work, look:

http://www.mapug-astronomy.net/astro...g/StarTest.htm

[Rui_Caratão]

Thank you for the link Ivan, I had already thought about using a diferent artificial star for testing.

[henry link]

Originally Posted by Rui_Caratão

I probably dont understand the all concept and the many variables envolved, but the way you put it, it sounds like a stopped down scope with SA could perform better than the same scope at full aperture.

Yes, stopping down a scope with SA reduces the SA. Spherical aberration happens when rays from the outer parts of the objective lens don't focus at the same distance behind the lens as rays from the central part of the objective lens. Simply blocking the unfocused outer rays eliminates part of the aberration.

All my star-test photos are done with an artificial star. Outdoors I use a small shiny ball reflecting the sun, usually placed about 40 meters from the scope.

Henry

[henry link]

Originally Posted by henry link

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.

I need to make a correction to part of the quote above. I had access to a Kowa 773 this past weekend and noticed that the Kowa 20-60x zoom also has barrel distortion, so I have seen it in an eyepiece before. In fact I had mentioned it in a test of the 883 a few years ago. So much for my aging memory cells. I frequently look through a friend's 883 and have never even noticed the barrel distortion in the field, so I doubt that I would find it objectionable in the Zen 25-50x either.

[dipped]

Originally Posted by henry link

Part 2 – The Zoom Eyepiece

I discovered, when I compared them, that the Zen 20-60x zoom eyepiece is a direct copy of the Swarovski 20-60x zoom. The focal lengths, lens diameters, overall dimensions and everything else I could measure are the same within the margins of error of my kitchen table and backyard methods. The photos of the two eyepieces placed side by side (Zen on the left) show identical reflection patterns of the camera flash returning from the lens elements. This only happens if the optical formulas are identical. So, whatever has been said about the excellent Swarovski eyepiece also applies to the Zen, which is such a faithful copy that I doubt anyone could tell the difference between the two. Both are very sharp and bright at every magnification with excellent off–axis performance. As is often the case with spotting scopes, it’s the objective and prisms that limit the high magnification performance, not the zoom eyepiece. Charles at Zen-Ray does not recommend it, but as you can see in the photo that shows the bayonets, the mounts are so close that Swarovski eyepieces will fit the Zen scope (but not engage the locking pin) and probably vice versa.

Henry Link

So a virtual clone is legally allowed in America of a European design?

I've just heard on the grapevine that the new upcoming RSPB HD Scope was put back for a redesign of the mount when it was discovered at a fairly late stage it was the same as the Swarovski scopes. As I understand it the RSPB were worried it could infringe design patents.

The RSPB scope is also shipping with a 25-50x zoom which potentially could have been used on a Swarovski if sold separately. If this is a clone of the swaro model ala the 20-60X Zen it could have really upset Swaro...

It sounds as if the RSPB scope is a variation of the Zen albeit more expensive as it will be around £1200. All should be revealed at the BirdFair in August...

This episode reminds me of the the non appearance of the Nikon Edg Mk1 bins in Europe.

[henry link]

Patent law is far from my field, but I imagine there could be legal issues in the US for these eyepieces, the Theron scope and probably other items that haven't yet been examined closely. I decided to simply report what I saw and leave the questions about intellectual property rights to others. If Swarovski or Nikon see reason for action I'm sure their lawyers know what to do.