Comparison of Baader Hyperion Aspheric 31mm with TS WA 32mm eyepiece on Startravel 120/600

Eyepieces:
Baader Hyperion Aspheric 31mm 72° 2"
TS WA 32mm 70° 2"
Telescope:
Skywatcher Startravel 120/600 on AZ3 mount with aluminum tripod
Baader T2 Maxbright diagonal with 2" Clicklock
Author:
Christoph Heinemann, Recklinghausen

Note: This is not a scientific work. I have determined the data to the best of my knowledge and belief, but I make no representations or warranties. The same applies to my observation results.

Determined or calculated data
Data for the
Eyepieces: Baader Hyperion Aspheric
31mm 72° TS WA
32mm 70°
External dimensions h=104mm / d=57.5mm
(measured by myself) h=110mm / d=56mm
(measured by myself)
Weight: 328g (Kitchen scale) 354g (Kitchen scale)
Lens 6, multi-coated (manufacturer) 5, multi-coated (manufacturer)
Eye relief 17mm (manufacturer) 24mm (manufacturer)
Field stop d=38mm (manufacturer) d=40mm (manufacturer)
Apparent field of view *) sGf=2 tan-1 (38mm/2 31mm)
=63.0° sGf=2 tan-1 (40mm/2 32mm)
=64.0°
Accessories M43 + SP54 camera thread
Filter thread,
Eyecups,
Dust caps,
Leather pouch, 1.25" adapter filter thread,
Dust caps,
Cleaning cloth
Price
(March 2023) €189 at Teleskop-Spezialisten, Munich €119 at Teleskop-Spezialisten, Munich
Telescope-Specific Data
Magnification V=600mm/31mm=19.4x V=600mm/32mm=18.8x
Exit Pupil AP=31mm·1/5=6.2mm AP=32mm·1/5=6.4mm
Actual Field of View rGf=2·tan-1(38mm/2·600mm)
=3.63° rGf=2·tan-1(40mm/2·600mm)
=3.82°

*) Pincushion and trapezoidal distortions, which increase the apparent field of view, are not taken into account here.
Due to the very low backfocus of my telescope, I use the T2 diagonal mirror listed at the beginning. The smaller aperture compared to 2" limits the field stop of the overview eyepiece to approximately 40mm if you don't want to see vignetting. For this reason, and because of the favorable exit pupils, I chose the two eyepieces I tested.
Karl Kloss from the telescope specialists in Munich was kind enough to lend me the two eyepieces for testing. I am very grateful to him for this, and therefore wrote this review.

Requirements
I have been interested in astronomy for some time, have read several books, and acquired a lot of theoretical knowledge (also through various forums). However, I have virtually no practical experience.
The telescope I am using, which I have owned since mid-January 2023, is my first and so far only one (besides a pair of TS WP 10x50 binoculars). Due to unfavorable weather conditions, I haven't been able to use it very often.
Since I got the two overview eyepieces (beginning of March 2023), the Unfortunately, weather conditions have worsened, so there haven't been many testing opportunities.
Initial Assessment
The eyepieces appear to be of high quality both visually and haptically, and they feel equally heavy. The TS WA has a glossy finish, while the Baader Hyperion has a matte finish. The rubber coating also appears to be of high quality on both and has no odor. The opening on the top (visible lens) is significantly larger on the TS WA than on the Baader Hyperion (34.5 mm compared to 25.5 mm, measured by myself). However, since the maximum usable exit pupil is approximately 7 mm (telescopes with an aperture ratio of approximately 1/4.5), this shouldn't make a difference.
If you hold the eyepieces side by side over a white sheet of paper, you can see no difference in light transmission and no discoloration of the image caused by the lens coating.
If you place the eyepieces in a bright location, you can see more reflections in the Baader Hyperion (right in the image) than in the TS WA (left in the image). The TS WA The reflections are also colored purple. The upper lens in the image is positioned slightly lower in the eyepiece of the TS WA than of the Baader Hyperion, which likely reduces reflections from light entering from the side. I initially considered removing the rubber eyecup on the TS WA to compensate for the lower position of the lens, but the result would have had no bearing on the real-world observation.

Night Sky Tests
Duration: Five nights of observation from March 8 to May 28, 2023
Locations: Recklinghausen Suderwich, in our own garden
Recklinghausen Suderwich, next to the model airfield
Attendorn
Conditions in Recklinghausen Suderwich:
- Light pollution from the southeast to west due to the Ruhr area, in the northwest due to the Marl Chemical Park
- Comparatively dark sky from north to east
- In the garden: Disturbing light from street lamps from north to southeast
Star groups in the south were observed in the garden, and star groups in the east at the model airfield.
Conditions in Attendorn:
- Very dark sky compared to Suderwich
Star groups were observed in the southeast to southwest.
During the first test in the garden, I focused the eyepieces one after the other on the moon. I noticed that the focal point of the Baader Hyperion is about 5mm further forward than that of the TS WA. For telescopes with very little backfocus, the Baader Hyperion has a decisive advantage. However, in my setup, there are no problems with the TS WA either.
I also checked directly whether vignetting was noticeable due to the small aperture of the T2 diagonal. This is not the case with any eyepiece; the edge of the field of view is sharply defined on both, and the stars do not noticeably lose brightness there. Further tests confirmed this observation. Eyepieces with a 40mm field stop are therefore unconditionally recommended in combination with T2 diagonals for visual observation. Photographically, this may be different, but that is not important to me.
Furthermore, it is clearly noticeable that the actual field of view of the TS WA is slightly larger than that of the Baader Hyperion (as expected due to the larger field stop). I don't notice any difference in the apparent field of view. The slightly higher magnification of the Baader Hyperion roughly "compensates" for the smaller actual field of view (see table).
The eye relief is pleasantly large in both eyepieces. The 7mm difference (see table) is likely roughly offset by the lower lens position in the TS WA. For eyeglass wearers, the rubber eyecups on both eyepieces can be folded down.
When observing in my own garden, I find the comparatively unsteady view through the Baader Hyperion annoying. The street lighting also causes (as previously feared) more distracting reflections in the eyepiece than with the TS WA. Here, the view seems more pleasant to me, and significantly fewer reflections are visible.
With the Baader Hyperion, the sky is depicted slightly darker, thus creating a higher contrast, which I initially viewed as a positive. However, due to the bright street lighting, my pupils are not so dilated that this difference could be attributed to the slightly narrower aperture compared to the TS WA. Diffuse light reflections in the TS WA from the street lighting are also not an explanation, as I observed the same effect at the model airfield. After some consideration, I can only explain the darker sky in the Baader Hyperion by the fact that it perhaps lets in slightly less light than the TS WA because it has one more lens. However, since no difference was noticeable between the eyepieces during the paper test, this remains a guess. I will therefore not include the darker sky in the rating.
With the Baader Hyperion, I like the point-like star image almost to the edge (approx. 10% of the diameter), which partially compensates for the somewhat smaller actual field of view. The distortion at the edges is barely noticeable during normal observation. With the TS WA, the image in the center of the field of view is also point-like, but at the edge of the field of view (approx. 20% of the diameter), there is more distortion, which (at least for me) is not particularly bothersome.

At the model airfield, the described impressions were largely confirmed.
The view into the Baader Hyperion is more pleasant than in the garden, which I believe is due to the more dilated pupils. Nevertheless, the view into the TS WA seems even more pleasant to me. Reflections in the eyepieces are not noticeable, but there is also no artificial lighting at the observation site.
While visiting relatives in Attendorn over the weekend, the weather forecast cooperated, so I took the telescope with me. This gave me the opportunity to test the eyepieces in a (virtually) dark sky, where they can unfold their full power.
The view through both eyepieces reveals significantly more faint stars here than in Recklinghausen. The on-axis star image is absolutely point-like with both eyepieces, with the Baader Hyperion extending almost to the edge. With the TS WA, the line-like distortions begin a little earlier (about 20%), but they still don't really bother me.
The sky now appears dark to me through both eyepieces, and I think I can make out one or two faint stars in the TS WA through indirect vision, which are being swallowed up by the Baader Hyperion.
The view is pleasant with both eyepieces, but feels even slightly better with the TS WA.
Overall, both eyepieces deliver convincing results under dark skies, making observing a pleasure.
Conclusion
Both eyepieces are highly recommended; both have their strengths and weaknesses, so it depends on personal circumstances and preferences which eyepiece is better.
If you value a particularly steady view or have distracting light sources at your observation location (which is generally not recommended), you should consider the TS WA. If a nearly point-like star image right to the edge or the shortest possible light path is important to you, you should consider the Baader Hyperion. This also applies to photographic use, as it has two threads for the camera connection (see table).
However, no statement can be made about the photographic image quality here, nor about the behavior of the eyepieces on another telescope.

It would have been interesting to have had an additional eyepiece from the >500€ range available, as I would have been able to better assess the image quality of the two eyepieces.

Baader Hyperion Aspheric 31mm 72° TS WA 32mm 70°
Pros - Less backfocus required (5mm)
- Sharp, point-like star image (approx. 90% of the diameter)
- Minimal distortion
at the edge of the field of view
(approx. 10% of the diameter), stars almost point-like - Sharp, point-like star image
(approx. 80% of the diameter)
- Slightly larger actual field of view
- Slightly more pleasant viewing
- Barely visible light reflections in the eyepiece under artificial light sources
Cons - Slightly smaller actual field of view
- Slightly more unsettled viewing, especially with poorly adapted pupils
- Disturbing light reflections in the eyepiece under artificial light sources - More backfocus required (5mm)
- Line-like distortions of stars at the edge of the field of view
(approx. 20% of the diameter)

Purchase Decision
It wasn't easy for me to decide for or against one of the two eyepieces. I even considered keeping both at one point. However, since they are too similar, it doesn't really make sense.
Ultimately, the deciding factor for my purchase is that I will continue to frequently observe from my own garden (due to time constraints and convenience). Therefore, the decision is in favor of the TS WA due to the more pleasant view and the significantly reduced reflections from street lighting. The slightly larger actual field of view is nice, but not the deciding factor, as the star image at the edges is poorer than with the Baader Hyperion.
When making your purchase decision, please note that the imaging properties of the eyepieces I describe are my personal impressions, which a second observer may only share to a limited extent or not at all. Therefore, it is definitely advisable to consult additional sources of information.

Sources
Baader Hyperion Aspheric 31mm:
https://www.teleskop-spezialisten.de/shop/Teleskop-Zubehoer/Okulare/Weitwinkel-Okulare-bis-80-GRAD/Baader-Okular-Hyperion-Aspheric-31mm-2-72-GRAD-Weitwinkel::2412.html
Manufacturer information:
https://www.baader-planetarium.com/de/31mm-hyperion-aspheric-2%22-okular.html
TS WA 32mm:
https://www.teleskop-spezialisten.de/shop/Teleskop-Zubehoer/Okulare/Weitwinkel-Okulare-bis-80-GRAD/TSWA32-TS-WA32-ERFLE-Weitwinkel-Okular-32mm-2-70-GRAD-Gesichtsfeld::2419.html
Manufacturer information:
https://www.teleskop-express.de/shop/product_info.php/info/p956_TS-Optics-32-mm-2----70--Weitwinkelokular.html
My diagonal mirror:
https://www.teleskop-spezialisten.de/shop/Teleskop-Zubehoer/Zenitspiegel-Zenitprisma/Baader-T2-90-GRAD-Maxbright-Zenitspiegel-mit-1/10-lambda-Oberflaechenguete::6201.html
Manufacturer information:
https://www.baader-planetarium.com/de/t-2--90%C2%B0-maxbright-zenitspiegel-mit-36mm-prism.html
My telescope:
https://www.teleskop-spezialisten.de/shop/Teleskope/Refraktor/120-130mm/Skywatcher-Startravel-120-auf-AZ-3-Montierung-Grossfeldrefraktor-Teleskop-120mm-600mm-f/5::227.html