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A comprehensive review of the Denk's LOA 21.

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#1 alarmclock

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Posted 14 September 2015 - 11:42 AM

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.

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#2 BillP

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Posted 14 September 2015 - 12:12 PM

Nice review.  Thanks!  Your caution on the star artifact when crossing the edge of the array is definitely correct.  I myself do not find it much of an issue given the other things this eyepiece is doing.  However, others may be bothered by it more than me.  What I feel is the major point with this new technology is what you said that all the familiar objects now appear *new*.  This is indeed their strength and what makes them so unique.



#3 REC

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Posted 14 September 2015 - 02:57 PM

That was a great review and I was especially interested on your observing points on each subject as I have almost the same scope as you, AD 10" f/5 but 1250mm vs 1200mm. One question though, a lot of your observations where listed at 50x and curious how you got that low magnification. Not sure what a TS BV is, but sounds like the Chinese ones out in the market like my WO version.

 

I am using a Denk. II with a Power Switch. I have to use and OCS for this scope to come to focus. At the lowest power it adds 1.3x which make the scope f/1625mm. With the 21mm LOA my lowest power is 75x. I would think you have to use a barlow or some kind of OCS to get your scope to focus? I also have the WO BV that came with a 1.6x barlow and that setup will not work in my 10" Dob. The only reason I keep it as it works with my 4" refractor without a OCS or barlow. In that f/1000mm scope, I get a wider FOV and a low power of 48x. So just curious how you got 50x in your setup.

 

I also agree with your build comment. When I slip them in the EP holder the fit is very snug. The only other EP that I have used out of many is my 16mm Brandon. I slowly fits in the barrel like a sucking motion and I get a perfect fit with little tightening.

 

Your description of the LOA array is also interesting. "We can notice that these squares are not arranged quite orthogonally". When I first got them and looked at the rear of the EP I wondered if they where defective? They looked like they where glued on and since Russ is building them by hand I wondered if his eye was off that day as they did not look evenly spaced? Also there seemed to be some smudges on them and strange looking reflections? Of course I have no idea how they work and if they where supposed to be that way. I looked at the paper that came with them and he had a picture of the array and said that this look is the way they are supposed to be to work properly. So, I just figured I'll just take a look through them and see how they work and maybe someone else on CN would chime in on this subject.  Glad to read that you did.....thank you!

 

You also answered another question I was thinking about. Do I need to use my Coma corrector. I was hoping not as I didn't want to add another piece of glass to the focuser and mess up my back focus.

 

Great comments in each object. I took mine out for the first time last night on a reasonable dark night and could see mag. 4.5 stars from my Red zone backyard. The transparency was pretty good and will be again tonight, so will use your notes on my observing list. I did not bring out my nebula filter out last night, but will try it on the objects you noted using one.

 

Between your review and Bill's review, I have plenty of good notes to follow-up with. :bow:

 

-Bob



#4 faackanders2

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Posted 14 September 2015 - 06:52 PM

I believe my arrays are all orthoginal, since 3D effect is left to right only on each individual array, and the near far bumps only work when at 6 or 12 o'clock positions.

 

Alarm clock, Nice report!



#5 REC

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Posted 15 September 2015 - 10:46 AM

I believe my arrays are all orthoginal, since 3D effect is left to right only on each individual array, and the near far bumps only work when at 6 or 12 o'clock positions.

 

Alarm clock, Nice report!

Orthoginal...not sure if I correctly know how this term is used to describe the array? Looking down at the rear of the EP the square in the center, it seems to be in the center but the glass square above it appears to have a slight tilt to it in reference to the top of the center square? The square under the center seems to be straight and not tilted like the one on the other side. So I'm not sure if this arrangement as to how they are aligned are the way they are supposed to be or is mine off a bit?

 

We need some pictures here of the bottom of the EP. I tried with my phone, but it was not successful. Maybe I'll have to use a real camera!

 

Anyone else care to chime in and report how they look to them? I have had my set for about 3 weeks and just stared using them this week. They seem to work ok, but I was having some issues on getting some of the single brighter stars pin point sharp?

 

-Bob



#6 alarmclock

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Posted 15 September 2015 - 11:24 AM

It seems that the squares are not orthogonal, by design. Your eyepieces are fine.



#7 REC

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Posted 15 September 2015 - 12:04 PM

It seems that the squares are not orthogonal, by design. Your eyepieces are fine.

Really, good to hear:)



#8 Joe Bergeron

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Posted 04 October 2015 - 08:55 AM

I don't see how these could possibly work unless the "squares" are actually weak prisms that slightly displace parts of the field. That's the only way the 3D effect could be achieved.



#9 alarmclock

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Posted 04 October 2015 - 01:12 PM

I don't see how these could possibly work unless the "squares" are actually weak prisms that slightly displace parts of the field. That's the only way the 3D effect could be achieved.

I guess that's how they work.



#10 TH1

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Posted 03 December 2015 - 08:21 PM

There should be no compromises here. The LOAs produce no artifacts when used correctly.

The user should be able to remove starlight where it should not be in the FOV with framing of the subject, and positioning of the stars in the Array. My newest example for this technique is M42 and the Trapezium central stars. It is very difficult to remove all unwanted effects from this object but with practice it's a minute tops to get everything going. If things still do not look copacetic it is because something is off. Either the eyepieces are not flush to their holders, the unit itself is not flush to the diagonal, the diagonal not in line with telescope, or direct light has entered the telescope.

That said, it's very possible all of these being aligned is actually working against the Array and it's very possible some slight single misalignment might actually favor some objects. IMO with 100 hrs+ in use.

 

Need further LOA time 😎


Edited by TH1, 03 December 2015 - 11:10 PM.


#11 faackanders2

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Posted 03 December 2015 - 10:14 PM

 

I believe my arrays are all orthoginal, since 3D effect is left to right only on each individual array, and the near far bumps only work when at 6 or 12 o'clock positions.

 

Alarm clock, Nice report!

Orthoginal...not sure if I correctly know how this term is used to describe the array? Looking down at the rear of the EP the square in the center, it seems to be in the center but the glass square above it appears to have a slight tilt to it in reference to the top of the center square? The square under the center seems to be straight and not tilted like the one on the other side. So I'm not sure if this arrangement as to how they are aligned are the way they are supposed to be or is mine off a bit?

 

We need some pictures here of the bottom of the EP. I tried with my phone, but it was not successful. Maybe I'll have to use a real camera!

 

Anyone else care to chime in and report how they look to them? I have had my set for about 3 weeks and just stared using them this week. They seem to work ok, but I was having some issues on getting some of the single brighter stars pin point sharp?

 

-Bob

 

All square sides and fringes should be parallel.  small angles from 6 and 12 o'clock may not be noticable and still have good 3D.  

3 and 9 o'clock rotations would not be 3D (and may just make vertical double stars).



#12 TH1

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Posted 14 December 2015 - 07:31 PM

Just to close mine out-

 

As much as astro companies are said by many to nickle and dime us to death, I would argue amatures are worse. The indecision and feet dragging for these products out there that ARE todays hobby has never been greater. People think China can get a 1000$ product down to 300$ so they hesitate. Plus they think something better is just a year away or less. 

 

Help these companies by buying their creations. If it is a lot of dollars for what you get, remember it's all R&D, and bills, and getting what you bought in a better form down the road. Help people out and buy it already and get out there.

 

You think you're going to live forever?

 

:waytogo:

 

 


Edited by TH1, 15 December 2015 - 01:30 PM.

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#13 faackanders2

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Posted 15 December 2015 - 11:11 PM

Just to close mine out-

 

As much as astro companies are said by many to nickle and dime us to death, I would argue amatures are worse. The indecision and feet dragging for these products out there that ARE todays hobby has never been greater. People think China can get a 1000$ product down to 300$ so they hesitate. Plus they think something better is just a year away or less. 

 

Help these companies by buying their creations. If it is a lot of dollars for what you get, remember it's all R&D, and bills, and getting what you bought in a better form down the road. Help people out and buy it already and get out there.

 

You think you're going to live forever?

 

:waytogo:

These sites provide free advertising as well as criticism and general discussion.  I believe Russ did a good job in providing discounts to the pre-order risk takers.  With his pending patent, Denkmeier can ensure he will have an exclusive market for a few years.

 

P.S.  Russ if you are reading this.  I believe you may have givern up to early on the night vision goggle device.  My club has one, and others on cloudy nights claim to see Bernards Loop, Rosetta, Flame all so easy.

 

Few realize Bell developed the jet engine only to abandon it because their first commercial version (Comet) didn't perform well.  And we all know where the future went.



#14 Lew Chilton

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Posted 17 December 2015 - 10:20 PM

Are the LOA 21s just a gimmick, or are they pioneering a new facet of our hobby? When I first heard about bino-viewing, I thought it was a gimmick, but today I own and enjoy using one.

#15 TH1

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Posted 17 December 2015 - 10:33 PM

No gimmicks Lew.

 

You should have heard a retired husband at our November star party. He couldn't get over the view. So much emotion. A real veteran amature. Amazing to see. The whole outreach crowd grew louder and were drawn to my scope. It fueled us all the rest of the night.

 

Do what you can to have a look. TH



#16 faackanders2

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Posted 17 December 2015 - 10:46 PM

Are the LOA 21s just a gimmick, or are they pioneering a new facet of our hobby? When I first heard about bino-viewing, I thought it was a gimmick, but today I own and enjoy using one.

Time will tell whether it is a "Fad" or not.  It definitely is different, fun and entertaining/exciting.  I do not have the 3rd non-3D (2D) eyepiece; but if this is your first eyepiece pair you may want to get the 3rd for planetary viewing (vs. buy a different pair for planetary right away).

 

Note I chose not to use the work gimmick or trick, but the 3D is artificially created using 5 arrays on the 3D eyepiece.  It is not true 3D  based on actual distances (which would require a computer and monitor).


Edited by faackanders2, 17 December 2015 - 10:47 PM.



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