Russell Optics 15mm and 19mm wide field Konigs
All observations discussed in this review were made using a 120mm f/8.3 Celestron XLT achromat. This scope is well corrected and capable of giving sharp flat field views.
The 15.0mm Konig has a 65 degree AFOV and ~16mm of eye relief. With the 120mm refractor, the magnification is 67x and the FOV is ~1 degree. This will be compared with a 14mm Pentax XW that gives 71x and ~1 degree FOV with the same scope. The 19.0mm Konig has a 70 degree AFOV. With the 120mm refractor the magnification is 53x and the FOV is 1.3 degrees. It will be compared with the 20mm Pentax XW that gives 50x and a 1.4 degree FOV with the same scope.
The barrels of Russell optics Konigs are constructed from hard, black Delrin plastic. The Delrin machines well as evidenced by the high quality of the eyepiece barrels. I also found that the Delrin is light, has a nice feel, is durable, and slides into and out of a star diagonal very smoothly.
All Russell optics Konigs are offered in a 2” format that is threaded for standard 48mm filters/adapters. The eyepieces have soft rubber eyecups that may be folded down for use with eyeglasses. Some of the Konig FL are also available in a 1.25” format.
As noted, the Delrin is light and both the 15mm and 19mm Konigs have a weight of 5.5oz. The optics provide a nice large eyelense. Coatings on the 15mm Konig were flawless. The 19mm eyepiece had one fine hairlike flaw in the coating that required a flashlight to see. This flaw does not affect the optical performance.
The evaluation presented here is a compilation of impressions from observations made over multiple nights, sky conditions, and lunar phases. My observing location is rural with generally dark skies but some light pollution detectable up to 20 degrees above the southern horizon.
It is important to keep in mind that in comparing the Russell Optics Konigs to the Pentax XW’s I felt that to provide a favorable overall assessment of the Konigs I needed to see performance that could truly rival the premium Pentax XW’s. I did not feel it is good enough to be able to say that the Russell Optics Konigs are “a good value for the cost”. I was looking for more than a “good value”. I was also evaluating whether or not I could conclude that the Konigs are a “great performer” - as the Pentax XW’s certainly are.
In this regard, criteria for what constitutes a “great performer” will vary to some extent with the individual. My criteria are: (a) excellent contrast; (b) on axis sharpness; (c) edge of field sharpness; (d) quality of field illumination including how even the illumination is across the field, brightness of the image, and overall quality of the light. (e) ease of eye placement.
As an eyeglass wearer, I also look for sufficient eye relief to be able to use my eyeglasses. The full field can be seen with eyeglasses in both the 15mm and 19mm Konigs – although the Pentax XW’s have more eye relief. Eye relief will not be mentioned further in this review, but I note here that if you wear eyeglasses while observing you can use both the 15mm and 19mm Konigs I tested while wearing eyeglasses.
Optical Performance Assessment
For the sake of simplicity I decided to rate the 15mm and 19mm Konigs against the 14mm and 20mm Pentax XW’s by giving the XW’s an arbitrary score of 10.0. This is not intended to imply that the Pentax XW’s are a “perfect 10” – but the XW’s are excellent in all categories.
With this 10 point scale a rating of 8 would indicate that in my evaluation the performance of the Konig is at 80% of the Pentax XW performance level. In instances in which the Konigs outperform the XW’s the Konigs would be given a rating higher than 10.
In addition to individual subjectivity, it should also be kept in mind that performance will be affected by the scope used. For example, while my Pentax XW’s are sharp close to the edge of the field in my f/8.3 achromat, recent observations with an f/5 achromat revealed that the XW’s showed considerable aberrations in the outer 25% of the field with the f/5 scope. So I cannot guarantee that performance I find satisfactory in my scope will be matched in other specific scopes.
The purpose of this review is to give a relative performance of the Russell optics Konigs to the Pentax XW’s using my 120mm f/8.3 achromat as a means of assessing whether or not the Konigs can give the high end performance advertised at a more wallet friendly cost.
Here I was looking for how black the sky background appears and how readily fine details appear to jump out. I swapped back and forth between the Konigs and the XW’s on multiple deep sky objects, the Moon, and Jupiter. Deep sky objects observed included emission and planetary nebula, open and globular clusters, and galaxies.
Contrast is excellent in both the Konigs and the XW’s. Most of the time I felt there was a very slight edge in contrast with the XW’s. I must emphasize that this edge was very subtle. I had to study specific objects for a long time with both eyepieces to come to any decision. My rating for the Konigs would be a 9.8 for contrast. But even here, there were moments when I thought maybe the slight edge should go to the Konigs. For example, in one instance I was studying the core of NGC 869 in the double cluster. I started with the 20mm XW. When I switched to the 19mm Konig there was unquestionably a greater ability to pick out stars in the core of the cluster. Stars that were barely detectable in the XW popped out in the 19mm. In another instance I when I switched from the 20mm XW to the 19mm Konig I clearly saw more fine details in the nebulosity with the Konig.
But this was not a universal result. In some objects - such as several globular star clusters, I felt that stars were very slightly more visible in the XW. The dark nebula in the M24 star cloud were a slightly deeper black with the XW’s.
In short, contrast performance in the Konigs was able to very closely match the high end performance of the XW’s.
Central Field sharpness
Here I was looking to see how tight a pinpoint could be achieved for star images in starfields, star clusters, and stars surrounding deep sky objects as well as how crisp lunar, planetary, and nebular views appeared.
As with contrast it was a real struggle to detect any significant difference in central field sharpness between the XW’s and the Russell optics Konigs. In viewing star clusters, it was possible to achieve as tight a focus with the Konigs as with the XW’s. When looking at nebula such as M-17 and M-27 - as well as galaxies, the details are as crisp in the Konigs as the XW’s. Lunar features were every bit as sharp in the Konigs as the XW’s.
There must be a slight central field sharpness advantage to the XW’s because I did find that it was slightly easier to find the sharpest focus point with the XW’s than with the Konigs. However, I also noted that when atmospheric turbulence decreases, this slight edge in sharpness is reduced. Overall, I give the Russell optics Konigs a 9.5 for central field sharpness. The Konigs are capable of matching the sharpness, and when they seem not be quite as sharp it is by a small amount that requires significant effort to detect.
Edge of field sharpness.
Edge performance is an important criteria to consider when evaluating eyepieces and is much of the motivation for the optical designs of expensive premium eyepieces. Edge of field sharpness was the only criteria I examined in which the Pentax XW’s significantly outperformed the Russell optics Konigs.
I estimated that astigmatism’s effects became detectable in the outer 30% of the field of the Konigs. It became severe in the outer 20%. For the XW’s the effects of astigmatism became noticeable in the outer 10% - 15% of the field. My rating for the edge of field performance relative to a 10 for the XW’s is a 7 for the Russell optics Konigs.
At this point I feel the need to clarify one aspect of edge performance. In an earlier review “Comments on low cost long focal length 2” eyepieces” I was critical of the poor edge performance of the low cost long focal length ~70 degree widefield eyepieces on the market. In the case of the mid-FL Konigs I do not find the edge performance to be as problematic as it is with the long FL eyepieces. There are several reasons. First, the purpose of a long FL wide field eyepiece is to grab as much sky as possible and take it all in. That is very hard to enjoy when the outer 30% of that view shows severe astigmatism. In the case of mid-FL eyepieces such as the 15mm and 19mm Konigs, I am working with magnifications where I am studying specific objects and the wide field serves to get the barrel out of the way and let me concentrate on the object I’m observing at the center of the field. Whereas poor edge performance in the Long FL widefields draws my attention, in the mid-FL Konigs I really don’t notice it as I’m studying various deep sky objects. Second, the astigmatism is more severe at the edge of the field in the long FL wide fields than in the Russell optics Konigs. Third, because magnifications are higher with mid-FL Konigs, less sky is visible in the FOV which results in fewer stars around the edge of the field and so the astigmatism effects are not as evident. The longer FL eyepieces have more sky in their fields and thus many more stars which makes the severe astigmatism that much more obvious.
So while I did not find the edge performance of the Konigs to be a problem for observing, the Pentax XW’s clearly have the edge in this category. Also keep in mind that the % of field astigmatism estimated above is what I see with my eyes and it is probable that my own eyes are contributing to the observed astigmatism. So if your own eyes lack astigmatism you may see even better edge performance.
There are 3 aspects of field illumination I considered. First is the evenness of the sky background. Ideally an eyepiece should show a nice even black background across the field. Most eyepieces I’ve looked through are decent in this regard, but some have been very poor. Second is the image brightness – an indication of how well light is getting through. Here I’m assessing this in a relative sense - how does the image brightness with the Konigs compare with the XW’s on the same object with the same scope.? Third is the quality of light. This is just an overall sense of the tone and quality of the colors.
I found the field illumination of the XW’s and the Konigs to be excellent. In both the XW’s and the Konigs at times the field was very slightly lighter in the outer 10% than the inner 90%. Overall, I felt that the evenness of the field illumination was actually slightly better in the Konigs and so for this category I give the Konigs a 10.5.
The Konigs have an image brightness that was essentially indistinguishable from the XW’s. Overall I felt that on some objects there was a very slight brightness edge to the XW’s so I give the Konigs a 9.8 for brightness.
The overall quality of the light from the Konigs was able to match the XW’s. In the early evenings, I have found that perhaps there is a 5%-10% edge to the XW’s. This difference is most evident when looking at red colored stars. However, here again, as sky conditions improved later into the night, the small differences essentially disappears. Lunar colors are exceptional in the Russell optics Konigs. I give the overall light quality of the Konigs a 9.5.
Eye placement of the Pentax XW’s is very comfortable. However, there can be some minor blackout with the XW’s if you have too much movement of eye position. In this regard the Konigs were superior. Eye placement is even easier in the Konigs than it is in the XW’s. I give the Konigs an 11 for this category.
Do the $65 Russell Optics Konigs rival the premium performance that the $350 Pentax XW’s give? The answer ends up being “It depends.” For contrast, central field sharpness, and field illumination it is very difficult to conclude that the Pentax XW’s have any significant performance edge over the Russell Optics Konigs. Any small performance edge assigned to the XW’s required careful scrutiny to identify and in each of these categories the Russell optics Konigs give a performance impression that is at least qualitatively 95% as good as the XW’s.
The only clear advantage of the XW’s is in edge of field performance. Since premium eyepieces are designed to provide sharp edge performance across wide fields, the Russell optics Konigs cannot be considered premium in this category. However, the edge performance of an eyepiece will also depend upon the quality and focal ratio of the instrument used, the sky conditions, and the eyes of the observer. What is considered satisfactory edge performance is very much a matter of individual preference.
Russell optics Konigs are more than a “great value”. They are great performers. Based upon my observations, performance of the Konigs is able to compete very closely with the Pentax XW’s in all categories except edge performance. If you’re looking for an eyepiece that can match the contrast, central field sharpness, and quality of field illumination of a premium eyepiece but are on a tight budget the Russell optics Konigs are an option worth considering. Perhaps the best way I can put it is to say that if I was forced to sell my widefield Pentax XW’s, I do not feel that I would enjoy observing any less if I only had the widefield Russell Optics Konigs.
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