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UO 24, 16 & 12mm Konig Eyepieces + 2.8x Klee Barlow
Submitted: Thursday, 7th April 2005 by Ian Ogilvie

Introduction

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UO Konig 24, 16, 12mm + 2.8x Klee Barlow

I must commence this review by stating that eyepiece preferences and selection are very personal things.  Everybody’s eyes are different and while reviews such as this one are useful, I recommend that if all possible you try before you buy.

I do not have any association with University Optics (UO) or any of the suppliers mentioned in this review. The comments in this review are merely my personal observations.

To assist the reader place my comments in context, the Konig eyepieces have been reviewed on the basis of my relatively limited experience.  While I have done quite a bit of observing over the last couple of years, in no way do I consider myself an experienced observer.  I have been most fortunate to have the opportunity to use a number of telescopes up to 20”, using a variety of interesting eyepieces from classic orthoscopic types through to some of the magnificent Televue products.

Background

After 30+ years casual observing with a couple of different scopes I joined the local astronomical society several years ago and had the opportunity to look through a variety of high quality eyepieces during deep sky nights.  The inevitable result was that I started looking to upgrade the eyepiece set I was using with my 8” F6 Dob.  My eyepiece set at this stage comprised Celestron brand, mid 90’s vintage; 25mm SMA, 32 & 10mm Plossls and a 2X Untima Barlow.  I started the search process by defining the basic selection criteria:

  1. Max Cost $150 per eyepiece. (If only I could afford Naglers!)
  2. Min Apparent Field of View (AFoV) of 60°. (Helps with a hand pushed Dob).
  3. Reasonable edge performance at F6.
  4. Range of focal lengths suitable for 1200mm focal length at F6.
  5. Eye placement not critical. (Some EP’s have fairly critical eye placement requirements and as a result can be quite tiring to use)

Having done some initial research via the web, I was in Melbourne on business and happened to drop into BATSC in Heidelberg looking for a “large” finderscope.  I found BATSC most helpful and having decided on a 70mm F5 refractor suitable for modification to a finderscope configuration I just had to spend some time looking at available eyepieces.  I acquired a 20mm 66° AFoV eyepiece that looked remarkably similar to an Orion Expanse type.  I found the shorter FL eyepieces in this range did not suit my eyes due to “kidney beaning”.

While I found the eye relief and eye placement characteristics of this eyepiece made it very easy and relaxing to use, I also found the focused image just a little too soft for my liking.

The next eyepiece I acquired was a 11mm 80° AFoV unit from Andrews Communications whom I also have found most helpful.  I believe this unit is manufactured by ZhiTong Industries in China.  I quite like this eyepiece although the useable AFoV is more like 70° and it does not like being barlowed.

My quest then led me to University Optics.  I was acquiring some ATM parts from them and also ordered a 16mm Konig eyepiece.  I was most impressed with this eyepiece, the inevitable result being an order for the 24 and 12mm versions and the 2.8X Klee Barlow.

My reasoning for the specific selection of eyepieces and Barlow was that by this stage I was also in the design phase of an 8” F6 “stringscope” dob and this eyepiece/Barlow set, as well as being compact and light weight, would give me a nice set of Field of View (FoV)/Exit Pupil/Magnification numbers as listed in the table below:

EyePiece

FoV°

Exit Pupil mm

Magnification

24mm

1.18

4

51

16mm

0.78

2.7

76

12mm

0.59

2

101

24mm + Barlow

0.42

1.4

142

16mm + Barlow

0.28

0.9

213

12mm + Barlow

0.21

0.7

284

Description

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Comparison of size & weight

All units are of high quality construction and very nicely finished.  They are of basic construction however, in that they do not come with eye guards, have smooth sides devoid of any form of non-slip grip and there is no safety undercut on the barrel.  The lenses appear to be fully multicoated as advertised, with blackened edges.  The Konigs were supplied in well made cardboard boxes with plastic end caps for both ends.  The Klee came in a similar box but only a lower end cap.

The Konig eyepieces are of similar size and weight to Plossl types and the photograph compares them to Celestron 32 and 10mm types.

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Comparison of barlows

The Klee Barlow is a remarkably compact type and is somewhat smaller and lighter than the compact Celestron Ultima Barlow as shown in the photograph.

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2 barlows end on

The Klee Barlow has a small field lens when compared to the Ultima as shown.  This may be one of the factors contributing to this Barlow’s reported vignetting tendency. This photo also shows to advantage the very high quality coatings used in the Ultima series eyepieces/Barlow.  The photo appears to indicate the Klee coatings have a higher level of reflectivity than the Ultima.

The eyepiece prices as listed on the UO Web Site on 29 March 2005 are:

  • Klee Barlow, 12mm Konig, 16mm Konig all $79.95 USD
  • 24mm Konig                                            $99.85 USD

Performance

I have used all three eyepieces and Barlow for the 18 months or so in my 8 inch F6 dob, as well as my Saxon 70mm f/5 refractor (finderscope).   I have also tested them on a limited basis in Meade and Celestron SCT’s at F10.

A note of caution.  I have also tried these eyepieces with a 30mm F4 binocular objective set up as a finderscope. The 24mm and 12mm are still usable (just) while the 16mm completely “falls apart” at this F ratio and I found it totally unusable.

My interest is predominately with deep sky objects, as a result the impressions I have gained with these eyepieces have been heavily influenced by their performance in this area.

On deep sky objects these eyepieces seem to perform quite well.  As well as offering performance comparable to high quality Plossl types, they offer an additional 10˚ AFoV that I find quite helpful when star hopping and while not an ultra wide FoV, the extra 10˚ certainly provides a more “immersive” experience that a Plossl can offer.

When observing the moon and planets, to avoid the astigmatism that is evident at F6, I find I need to keep the object within the central 50% of the FoV.  However, the situation changes when using the Klee Barlow when almost the entire FoV (95%+) becomes usable for high definition viewing.  I have not seen any evidence of ghosting or internal reflections with bright objects.

As best as I can measure them the AFoV and focal length for all three eyepieces are as advertised.

Overall these eyepieces could be considered similar to high quality Plossl type with a greater AFoV (60° as opposed to 50-52°) and slightly increased eye relief.  They do however appear to be more sensitive to reducing F ratio.  I have found them parfocal within 2mm and, when used with the Klee Barlow, almost perfectly parfocal.

24mm Konig II

This is a pleasant eyepiece to use with just sufficient eye relief to allow the use of glasses if required.  It is not fussy about eye position and I have not seen any sign of kidney bean or blackout. 

Stars snap into focus as very tight pinpoints with excellent contrast and no evidence of ghosting or internal reflections.  I have not seen any evidence of field curvature but it does suffer from increasing astigmatism at the edge of the field with reducing F ratio.  However, it is quite useful at F5, good at F6 and excellent at F10. 

12mm Konig II

I have listed this eyepiece next as my comments are almost identical to the 24mm with the exception of eye relief which will not allow the use of glasses.  The eye relief is approaching eyelash distance, however, due to the size of the eye lens I find I can, with care, position my eye so as to keep eyelash oil away from the lens.

Due to its small size and tapered top, it can be somewhat difficult to grasp and remove from focuser units, particularly when wearing thick gloves.

16mm Konig II

This eyepiece is somewhat different to the other two in that it has a larger AFoV of 68°.  I am not sure why UO have done this, as the effect of the larger field stop is a reduction of eye relief to inside eyelash distance.  In addition I have found the last 10% or so of the AFoV almost unusable at F6 due to astigmatism.

Ultimately, to make the eyepiece easier to use, I fabricated a new field stop of reduced diameter to provide a new AFoV of 60°.  This has increased the eye relief to a more usable level and the area outside 60° that was affected by significant astigmatism is now hidden by the field stop.

Like the other König’s, stars snap into focus as very tight pinpoints in this eyepiece with excellent contrast and no evidence of ghosting or internal reflections.  I have not seen any evidence of field curvature, but like the other UO Königs it does suffer from increasing astigmatism at the edge of the field with reducing F ratio. It is quite useful at F6 and excellent at F10.  I personally find the astigmatism displayed by this eyepiece excessive at F5.

2.8X Klee Barlow

This unit is very small and light, it does not appear to introduce any undesirable aberrations and is well matched to the three König eyepieces in this review.

A note of caution: I have seen comments in various web sites that this the Klee Barlow can introduce vignetting with some eyepieces and F ratios.  I have noted it severely vignettes my 11mm Andrews (ZhiTong) UWA eyepiece.  However, with the three UO Königs I have not seen any evidence of this.

Apart from the increasing magnification, the most noticeable effect of this Barlow is all three eyepieces are almost exactly parfocal and the edge of field astigmatism completely disappears.  For planetary use I have found König/Klee combination very sharp and useable almost right to the edge.

 

Summary

Liked

  • Price
  • Weight/Size
  • Sharpness and Contrast
  • Performance above F6
  • Wider AFoV compared to a Plossl
  • Nicely matched set with or without the Klee Barlow

Not Liked

  • No eye guard.
  • No non-slip grip.
  • No safety undercut.
  • 12mm is very low profile and can be hard to grasp when wearing gloves. Its profile also makes it hard to fit dew heater elements.
  • Klee Barlow only came with lower end cap.
  • 16mm field stop too large for comfort.
  • Significant astigmatism below F6.

Knowing what I know now, would I make the same decision again?

For me, the answer is yes, as this will provide a balanced and complete eyepiece set for my F6 “stringscope”.

Overall

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The set

I have found the UO Konig II eyepieces and Klee Barlow covered in this review to be a high quality set of eyepieces with a good performance/price ratio subject to the inherent F ratio/eye relief limitations.

Review by Ian Ogilvie (stringscope). Discuss this review at the IceInSpace Forums.

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