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Comparison of 35mm Panoptic to Williams Optics 40mm 72 degree widefield.
Physical comparisons:
Televue 35mm Panoptic:
Heavier than the Williams Optics 40mm, excellent machining on the eyepiece barrel, and sharp anodizing, well cut formed and fit rubber grip. The 2? end of the eyepiece seems to be stainless or chromed steel, perhaps accounting for part of the additional weight. According to the TV website the 35mm Pan has 6 optical elements in 4 groups. Coatings apparently of two types, both distinct green and magenta colorings both on and off axis, quality of coatings excellent. Rubber eyecup extends approximately ¼ inch very flexible and caps are well fitting. I prefer the fluorescent green lettering, which is done with great accuracy.
Williams Optics 40MM:
Excellent machining, the 2? end of the eyepiece seems to be an aluminum machining, also sharply anodized, and well machined on a par with the TV. Has dual rubber grip panels, both well cut and fitted. Slightly smaller in diameter than the TV but also slightly taller. The WO 40mm also has the traditional WO tapered telescope end (which as noted earlier is an aluminum anodized part) rather than the indent that is more common in the industry, both serve the same purpose. Coatings also apparently of two types, distinct green and magenta colorings both on and off axis. Less internal reflections because of fewer optical elements. According to the WO website the 40mm has 5 optical elements in 3 groups. Does the number of optical elements indicate superior design and performance? More on that later. Williams?? silver lettering on the black anodizing provides a good contrast and is slightly larger than the TV lettering, I just like the TV green. The eyecup on the WO extends 3/8 of an inch and is likewise very pliable and flexible.
My setup: a home assembled 203mm fast Achromat of 1192MM focal length F5.87 on an Altazimuth mount, with a Starlight Instruments 3.5? feather touch focuser. This combination was developed for wide field messier use and more specifically for nebula and globular clusters, and low power lunar observing and occultations of planets and widefield objects.
Performance:
These two eyepieces would give magnifications of 34x for the 35mm Pan and 30x for the WO 40mm. For the Pan a 5.96mm exit pupil and a 6.8 exit pupil for the WO 40mm; while the 35mm Pan had a true 2 degree field and the WO 40mm had a 2.4 degree field; these statistics complete the performance specifications for both eyepieces. Perhaps it would have been better to compare the 33mm WO with the 35mm Pan (but this is my first WO eyepeice) but I was looking for a wide field eyepiece to replace my 55MM TV Plossl which because of the large exit pupil in my particular setup was not as comfortable to use as my 35MM Pan, the WO 40mm by coincidence has the same true field as the 55mm Plossl because of the wider apparent field. Well I couldn;t wait for some clear skies to do some comparisons.
Well excitement doesn??t always go along with excellent observing opportunities, the skies were as dark as they get for me in my suburban back yard, no moon and no surface lights, seeing was only 3 out of five and the transparency was the same, there was an occasional five mph wind.
For a visual comparison it was decided to use objects that I would use these eyepieces for specifically with my telescope setup. That would be nebulas and globular clusters. My favorite nebula was visible so on it was to M42 in Orion. With an 8? scope there are sufficient stars in the field to use as benchmarks for measuring the visible extent of the nebulosity and also for use in determining limiting magnitude. So first off goes my 35mm Pan, clarity was achieved by focusing on the trapezium for best focus, the Starlight focuser making quick and accurate work of that. The nebulosity easily extended for about 1/2 of a degree across the field, darker patches and wisps were visible along with some stars that were initially confirmed with averted vision. Okay now on to the WO 40mm. Although I had to change eyepieces often, because of the wide field views of each my AltAz setup was not a problem; and ample time was allowed for settling down and realigning after changing eyepieces. The spurious chromatic aberration from my fast Achromat was not excessive or more pronounced with either eyepiece, sweeping through Orion??s belt only resulted in purple airy discs around the brightest stars. It seems that the stars were slightly clearer at the edge of the field of view with the WO 40mm. But I was hard pressed otherwise to distinguish any difference in the optical performance of the two eyepieces. The extent of the nebulosity or clarity of faint extended objects was equal as was the ability to perceive faint stars in the field of view. It seemed that the WO 40mm was easier to obtain the proper eye position for the optical axis, but again just barely.
After an hour of changing back and forth and not being able to declare either eyepiece a definitive winner on clarity of extended nebulosity it was on to another test, M41 in Canis Major. I needed a few more stars in the field to judge clarity of faint star images and I always like the contrast of the orange star near the center of the cluster, the 150 stars spread over its 38?? diameter to 13th magnitude will give me plenty of points for comparison. Again, I started with the 35mm Pan and went back and forth between it and the WO 40mm for about an hour. I looked for stars just at the edge of visibility more easily seen by averted vision then carefully confirmed visibility, there were many reference points for comparison and to confirm locations between eyepieces, but try as hard as I could I could see no difference in acuity between the eyepieces. The many stars in various locations gave a good analysis of the optical field from several points, and clarity and definition was indistinguishable between the two eyepieces.
Final decision:
Everyone will have to make this decision for themselves, but as for me and my particular setup (large fast Achromat), which except for potential chromatic aberrations and curvature of field does not push eyepieces to their maximum magnification potential, I am well pleased with the WO 40mm as compared to my Pan 35MM, and for optical results would not choose one over the other. However I like the idea of getting a WO 40mm, WO33mm, and WO 25mm for the price of a TV 35mm Panoptic. This WO 40mm is a keeper. The award goes to WO for affordability, always an aspect that makes a hobby more palatabe to my understanding wife :)
Robert Gibbonsmeyers
Saint Charles, Missouri USA
203mm F/5.87 Achromat with Starlight Instruments 3.5? focuser.
Rating:  [5 of 5 SWANs!] |
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