Hi!
This is a review of the LOA I translated from my native language to English. Please forgive the possible errors.
Pre-ordering in March, delivery last week, I can say that it’s been a long wait to have at least the honor to try these eyepieces, claimed to be revolutionnary by the company Denkmeier. Russ, their creator, did a lot of teasing on cloudynights, and the first user reviews following the production line were more than promising…
Unboxing, we find for each eyepiece an helicoidal threaded plastic box, really handy, and the classic rubber caps, which fits firmly.
Aesthetically, the eyepieces give a feeling of sturdiness and simplicity. The bodies are black anodized aluminum, and the design plain. Compact, dense, and well manufactured, they exude quality.
Mecanically, nothing to complain about. The 1 »1/4 barrels slide gently in the eyepiece holder, proof of an accurate machining process. There is no undercut, and this is good news for both screw and annulus lock holders systems.
About comfort now. Be it the focal choice (21mm), the apparent field (65°), the reasonnable weight and the tiny format, the large front lens and the long eye relief, the intuitive and easy eye placement, it’s for sure that Denk knows binoviewers users and their expectations. On this topic, the LOA are perfect, no more, no less. It is very easy to find one optimal observing position, and keeping it effortlessly.
Optically, the field doesn’t suffer from coma that much at F/5. They’re not as efficient as high-end eyepieces from Televue or Pentax, but the field is really usable without athe need of a Paracorr. On a daytime test, I noticed that geomety of the field is on the flat side, and the colors neutral. At night, definition is excellent, and contrast wonderful. Side by side, my 20mm SWAN are really dull compared to the LOA. You have the good Plossl feel, plus apparent field, plus corrected field, plus comfort.
But what are those LOA really? It’s a pair of eyepieces designed to be used with a binocular device (binoviewer, big binoculars, binoscope). Their main feature is to deliver say « 3D » images for deep sky observing specifically.
The « neutral » eyepiece, in it’s look, doesn’t seem different from a conventionnal eyepiece. The « active » one contains the Lederman Optical Array. The array is composed of 5 squares glued under the front lens. We can notice that these squares are not arranged quite orthogonally. Glye is « optical » and is indeed invisible on the field.

How do they work? Unfortunately (for us), the design is patented, and the secret well kept, Russ doesn’t talks at all about the optical principles associated with this array. Myself not being an optician, I have no actual idea of how it could work.
On the active eyepiece, there is a bumpy rubber N (Near), which we will place facing oneself, or opposite (180°), rotating the eyepiece in the holder :
- N facing you, the center of the field is « in front of », and seems to float before your eyes.
- N the opposite way, the center of the field goes « at the back », and seems lost, far away into space.
So how are they performing on the sky, you may ask? Before answering this question, I would insist on the fact that you should comply with the prerequisites needed for correct exploitation of this system. My first observing sessions with the LOA were really disappointing because I hadn’t followed these advices :
- use a properly collimated binoviewer. Most of high-end binoviewers (Baader, Denkmeier, Televue, Siebert, Zeiss…) are well tuned out of the box. But it wasn’t the case with my cheap TS, for which I had to manually collimate the prisms. Where this wasn’t an issue with my other eyepueces, the LOA seems to be much more fussy on this topic.
- do observe under dark skies. The LOA need reasonnably dark skies to unleash their power. Under my no-so-dark sky (milky way visible at zenith in summer), it’s good enough it seems, but I can’t wait to try them our under pristine skies. I also could’nt test them under the moonglow.
- have the necessary gear to adjust magnification before the binoviewer (PowerSwitch, Extender, OCS, barlows, powermates..). Object framing is vital with LOA, and this is mainly a scaling exercice you need to be prepared for.
Now on to the actual observations!
(Scope used is an Orion 10 inch F/5)
M11 : 50X, « far », no filter The cluster seems to sit behind the rich star fied. It’s like travelling towards it, down there, far away. Distance feels real, this is abysmal.
M31 : 50X, « near », no filter. No 3D effect with this wide target, but the excellent contrast generated allows a dark lane to be seen, unspottable usually from this observing site with this instrument.
M13 : 50X, « near », no filter. Nice pinpoint stars at this low magnification. The cluster is clearly in the foreground, like suspended in front of your eyes.
M92 : 120x, « far », no filter. As for M11, this globular seems unreachable, far from us. Very realist view.
M71 : 120X, « far », no filter. This object has never impressed me before. I spend 20 minutes on it this time, and it’s been the start for a « walk » in the surroundings. The deepness of the image is astonishing.
Double-Amas : 50X, « far », no filter. As the object scrolls slowly, it morphes gradually, as if you were flying around it and the parallax destructuring its shape. Very different from the usual view, but pretty exciting.
M57 : 120X, « near », UHC filter. The ring seems to be floating at the foreground, almost at reach. Nice shades of grey inside. My best observation for this object so far with this scope.
M27 : à 120X, « far » UHC filter. Dumbell, lost in space. A glimpse of the central star. Pretty.
M17 : 50X, « far », UHC filter. Sky is too polluted down there, but the extensions are unusually obvious.
M52 : 50X, « far », no filter. This is an object I seldom visit. It won’t be the case anymore!
NGC 457 : 50X, « near », no filter. A spectacular cluster with the LOA’s, framing of the object is however tricky.
Rose de Caroline : 50X et 120X, « far », no filter. Very well resolved, the cluster reveals its dark lines in a sweet sparkling fashion.
Albiréo : 50X, « near », no filter. The gem in front of the eyes, and the milky way spreading in 3D in the background. Spectacular.
Veil complex : 50X, « near », UHC filter. Difficult object under my skies, but the surroundings are however splendid, with its numerous star clusters suspended at different depths.
You’d have understood, I have seldom been that much astonished than this night. These objects, observed for years, through different telescopes, eyepieces, filters, skies… look… New. The re-discovery is total, not to say baffling at first. One would need to use his one eyes and brain to this new observing fashion….and my other eyepieces are shivering with fear in their boxes.
What surprises me, is that the effect you get is definitely not a « theatre » 3D, right in your face. Instead, it’s more about a natural feeling of hovering, or diving. You leave the abstraction of a flat image, and live it instead. No sensationalism. It’s really beautyful. But, I coul’nt insist more on the subtlety of the effect, which might disappoint the impatient or the scientific type of observer. These LOA are built for the contemplative.
To such a point that you can be hooked by the view on the way while looking for an object, which I haven’t done under my skies since a long time. Composing the perspective of a scene (rotation of the eyepiece, magnification, framing in the field) allows a great fun and a lot of enjoyment.
The comfort provided is such that the observing time increases a lot for a given target, enabling you to spot more details and subtleties than ever; contrast seems fairly boosted. In other words, the enjoyable feeling that you « are » there, gives the will to stay longer. Consequence, the quality of the observations increases.
But there is a downside.
LOA’s have a major problem, well known and discussed here and there. Do you remember the array’s squares that I was mentioning before? Well, every time a bright star crosses the edge of one of those squares, it generates an artefact of itself for a few seconds, a kind of ghost image. This is indeed visible most of the time you’re using the LOA’S, as soon as there are bright stars in the field. It’s one’s decision to weight this downside, relative to the overall picture.
I would advise if possible to try in depth these eyepieces before buying them; they will not please every observer, and the bill is on the high side. But it is now obvious that, for once, the adds tell the truth : this is a revolution.
‘clock
Edited by alarmclock, 14 September 2015 - 11:48 AM.
