[COLOR="Navy"]Burgess TMB Planetary Eyepiece Comparison Report and Review[/COLOR]
I would like to begin this report with some explanation of the goals of the tests.
My intent was to find out which eyepieces performed best on axis, off-axis and to what degree as well as look for other problems that might effect performance.
Mostly I was concerned with planetary, but a second perspective was DSO viewing.
I also included comfort, eye position and eye relief because these are important for making a planetary eyepiece more useable in my opinion.
I also would like to point out that the differences on axis were rather small and that the biggest differences were edge and aberrations. So this is why the aberrations were listed and considered in the overall view as well as throughput, reflections and quality of construction.
The tests were performed in dark skies (Mt Pinos 14.5” f/4.3 Starmaster)) and light polluted skies (backyard, Bakersfield, Ca 10” f/6 Zambuto Astro Sky Dob)) to give a little variety in the viewing conditions. I felt this was needed to try to see them in everyone’s perspective viewing conditions.
Every attempt was made to have like focal length and FOV in each of the eyepieces compared in this report. In some cases it was not an exact match, but I felt that it was close enough to be realistic and fair.
Eyepieces used were the following types.
1) Burgess Optics TMB Planetary 4mm, 5mm, 7mm, 9mm
2) Televue Radian 4mm, 5mm
3) Televue Nagler T-6 5mm, 7mm, 9mm
4) UO Orthos HD series 5mm, 7mm
5) Circle-T Orthos (generic) 9mm
6) Orion Expanse 9mm
70 Pentax XL 5.2mm, 7mm
The test was repeated every few minutes to try to get different atmospheric conditions so that I could see the best possible contrast, detail, edge and scatter data. If it appeared that the one eyepiece was out performing another, the other eyepiece was immediately placed in the focuser to get a quick comparison to try and eliminate the possibility of one getting a better window than the other.
I did enlist the help of Rod Kaufman on Mt Pinos for the 4mm, and 5mm test. We used Jupiter for all testing on that night when we tested together. Later I used DSO for some independent testing on DSO objects such as planetary nebula and globular clusters for resolution testing.
Ok, I guess I should give the results first, naming the eyepieces and their placement.
1) Pentax XL ( best throughput and image detail on Jupiter)
2) Radian (very close second I might add)
3) BO TMB ( because of FOV and eye relief)
4) UO HD, Circle-T Ortho (due to eye relief and FOV)
5) Nagler T-6 (rating reflected the amount of aberrations)
6) Orion Expanse
Now I will try to explain the results.
#1 PENTAX XL
Pentax won the overall because of its superior contrast, detail and lack of aberration. It had a slight edge on throughput too. It would show a star in the field that all but it and the Radian did not reveal. It was a clear winner, but the differences were subtle but definite.
Each time it was placed in the focuser, you could see a field star that was close to mag 16 that the UO HD, BO TMB, Circle-T and Nagler would not show with direct vision, though it would show with averted vision with the BO and Orthos. This was a small thing, but it definitely proved which eyepiece was performing the best as far as limiting magnitude was concerned. Also the banding and festoons were easier to see and stood out to a greater degree with the XL. The limb of the planet showed less scatter and the overall image of the disc was sharper with more contrast against the sky. Edge was clean to 5-10% with no distortion and almost no color. No flaring with bright objects just out of the FOV was noted. 20mm eye relief makes them a good choice for those who wear glasses. The adjustable eyecup worked well and kept reflections or the eye to a minimum.
#2 TELEVUE RADIAN
The Radian was a close second. It had the same high contrast, detail and throughput, but did show more edge color and degradation than the XL. There was a little color at about 10% from the edge. This color was slight and matched the edge performance of the BO TMB. The TMB showed less color (but some distortion) in some focal lengths, but the same in others. The Radian also gave a crisp limb and good contrast with the black sky. The bands were darker and the festoons were more pronounced like with the Pentax. There was little scatter induced by the eyepiece. No flaring was noted with the Radian. 20mm eye relief again makes it a good choice for those who wear glasses. The Insta-Adjust works well, but is not as stable, it can be moved by hitting it with your face, but it does work well to eliminate reflections of the eye.
#3 BURGESS TMB
The Burgess TMB eyepiece was a good performer and would possibly have placed second except for the throughput, reflection and contrast issues. The banding and festoons were more faded and did not stand out as they did in the Pentax and Radian eyepieces, possibly due to the cooler coatings. The details were there and the view was sharp, but the contrast just was not as revealing. You had to look harder to see the same details on Jupiter. I think this is due to coatings, but might also be scatter. There was a little more scatter around the limb of Jupiter, which made it not stand out as well. This was a slight difference, but was there on all focal lengths. Some focal lengths did show a little more flaring (reflections) than others (7mm, 9mm) and the 9mm displayed a bit of field curvature (25% from edge) as well as some color and degradation of image at 10% from the edge. There was a slight amount of field curvature seen in others too, but the amount was small and did not cause real refocusing issues. The color on edge was very similar to the Radian in amount and degree. The 4mm and 5mm showed little color but some degrading of the image at 10% from the edge (darkened disc with loss of detail) , again the same intensity as the Radian, but without the color. Field curvature was noted in some focal lengths with the most in the 9mm. The 7mm and 9mm also showed the most flaring when Jupiter was placed just outside the FOV. This was probably due to the interior of the EP and field stop being a bit reflective and not as flat blackened as I would have liked. Also could be due to lack of blackening of the lens edges? Eye relief was good on all focal lengths and will work with glasses though some were close when I put glasses on, but all were useable.
I disagree with others that have stated that the edge was clean, there was some color or Jupiter would turn ruddy when it was placed at the edge. Field curvature is another thing that I have not read about when people reviewed these eyepieces in the past. The edge performance was very close to that of the Radian, which is not what other reviewers have reported as they stated the Radian had a lot more edge problems than I saw in my tests. In fact with most the color and edge looked almost identical in both eyepieces. I also found that the Radian had a slight edge on throughput and had less scatter than the BO TMB.
But all that said, the BO TMB is a good eyepiece and a very good value. It was certainly a good match and was somewhat better than the UO HD Ortho and Circle-T so it is a good performer indeed if you consider on-axis performance and FOV as well as comfort and eye relief.
#4 OU HD - CIRCLE-T ORTHOSCOPIC
The Orthoscopic eyepieces performed very closely. There was little difference between the UO and the Circle-T eyepieces. The difference in focal length makes it hard to compare them side by side. So I will just say they were tied.
Contrast and detail were about the same as the BO TMB. The scatter was minimal and the edge was clean without color or distortion. The overall would have made them rate higher if they had not lacked in comfort as well as eye relief. The throughput issue also brought them down in rating a little. There was no flaring noted on any Ortho. The clarity was good, but did seem to be slightly less than the Pentax and Radian. Overall the image was good. The eye relief was tight and eye glasses were a problem. These eyepieces are a good value, but just not as nice to use as the others when you compared them side by side. The smaller lens was not a fulfilling to use. The FOV was tight compared to the others and this again was less pleasing. Rod and I both felt that they just did not perform as well, but the differences that were noted were small.
I guess that the Orthos could have faired better if they had been compared to eyepieces that were closer to them in FOV and eye relief. I would grant them a good value and performer if eye relief and FOV are not a concern.
#5 TELEVUE NAGLER T-6
The Nagler eyepieces had good on axis performance but had a lot of edge problems with distortion and color when used as planetary eyepieces. The contrast on Jupiter was good and the banding was actually more pronounced with them than the BO TMB. But the throughput was off a little from the other eyepieces and with the larger percentage of FOV lost to aberration so they just did not fare well. There was distortion of Jupiter, stretching and discoloration starting at 20% or so from the edge. Eye relief was tight and did not afford enough for glasses. No flaring was noted and the interior was well blackened. Quality in the build was very good and coatings were nice.
These eyepieces were just not designed for planetary I feel and are more applicable to DSO viewing where FOV is more important and edge performance not as critical.
Overall rating would be a good DSO eyepiece with too tight of eye relief for those who wear glasses.
#6 ORION EXPANSE
I added the Orion Expanse to the test to have another 9mm eyepiece for the test. It is a decent eyepiece but is not in the same league as the others in the test in my opinion. I will just state that the on axis performance is pretty comparable, but off axis it has a bit of an issue. Lots of degradation of image at 20% or so is noted, with color as well as flaring (reflection) and scatter issues on the excessive side. The eye relief is long, but eye position is critical and makes it not as comfortable to use even though it has plenty of eye relief.
It did not do as badly as one might have predicted though when on axis was judged. It was comparable to the others on detail shown, but contrast was off a bit.
[COLOR="Blue"]CONCLUSIONS[/COLOR]
I feel that the BO TMB is a good (at the sale price) value and is a good alternative to the Orthoscopic. It has more eye relief and equal or better overall performance because of comfort and FOV and on-axis detail performance. The images were very good on planetary, and the DSO images were also quite good. I got nice resolution with them on Globular Clusters and Planetary Nebula. There was a nice clean field and the stars were, for the most part, sharp and clean with the exception of the 9mm and its field curvature. I liked the eyepieces and found the quality of construction as well as the functionality and eye relief was good for this priced eyepiece. The interiors could used better blackening as well as the field stop and perhaps the lens edges. I did not disassemble these, but someone that did stated that edges of the lenses were not all blackened and had rough edges. I cannot confirm this however and did not see this with a loop when I inspected them. Perhaps it would require disassembly to see this. The adjustable eyecup is quite nice to use and the guard does block most external reflections from the eye.
[COLOR="Blue"]FOLLOW-UP[/COLOR]
These will stay in the box and the new ver2 6mm will be added when it becomes available so that I can give it a try compared to the 6mm Radian.. The 3.2mm and 8mm will be shipped to me as soon as they arrive too and I look forward to trying them as well.
I would have to state that if you do not have a set of planetary eyepieces and do not want to spend 100’s of dollars per eyepiece, then these are a good choice. Perhaps not as good as the very high end planetary specialty eyepieces that are sold today, but the cost is much lower and they do rate well in my book.
I wish I had had access to the high-end planetary eyepieces for the test, Zeis, Pentax Orthos and such, but they were not to be found.
Though the Pentax XL and the Radian had their edge of performance in my opinions as well as in Rod’s conclusions, they do cost several times more that the BO TMB and the performance was very close.
The Orthoscopic eyepieces performed well, but just lost out for various reasons. They still too are a good value and performer and should not be considered a loser really.
I would like to point out that the Nagler T-6 eyepieces, though they did not do well in this test, are still excellent eyepieces when used for the type observing that they were design to do, mainly DSO.
Rod did state that the real shocker was the Pentax 5.2mm XL, with it high throughput and wonderful contrast and clarity compared to the other 5mm eyepieces. He did not expect it to be as great a performer as it was, even though he owned a 10.5mm XL and finds it to be excellent. There was just something special about the view through this eyepiece.
Floyd Blue
Moderator Eyepiece Forum
