Hyperion 24mm Wide Field

The New Hyperion 24mm Wide Field
By William Paolini



Introduction

With Baader's recent introduction of the 24mm Hyperion, the 1.25" Hyperion line of 68 degree AFOV, 20mm eye relief, modular wide field eyepieces is now complete. So it was with much anticipation I ordered one of these sweet new additions to the line to see how it performed.

As with all Hyperions, it arrived with one bottom cap, two top caps (one that fits with the eye guard up and the other fitting the eye guard rolled down), and a black faux leather draw string bag. First impressions, out of the box are that the new 24mm Hyperion is a well crafted eyepiece, in line with rest of the available Hyperions. The rubber eye guard is the same as on all Hyperions, where you have the choice of keeping it folded down (like the 5mm in the group photo), or extended up where it provides approximately 3/8 inch of eye guard extension above the folded down position. The deviation point of this Hyperion from the rest of the line is found in the 1.25" barrel. All the Hyperions of shorter focal length have a lens grouping housed within the 1.25" barrel, so when you remove that section and insert a Fine Tuning Ring you can adjust the resulting focal length of the eyepiece. In the 24mm's case, there are no lenses housed in the 1.25" barrel. So while fine tuning rings can still be inserted, they will have no affect. You can however insert a 2" filter instead if you chose to use and existing 2" filter and did not have that particular filter in a 1.25" format.


Field Performance






Enough time looking at the eyepiece, it was now time to look through it instead! Over a period of several days in early October I put the new 24mm Hyperion through its paces on a wide variety of celestial targets. The telescope used was the Orion XT10i 10" f/4.7 Dobsonian as I wanted to see how this eyepiece performed in fast Newtonian optics. The targets I examined over the several days of testing included: Vega (Magnitude 0), Deneb (Magnitude 1.3), Polaris (Magnitude 2), Altair (Magnitude .75), Albierio (Magnitude 3.4), Mirach (Magnitude 2), and Alderamin (Magnitude 2.5), Open Cluster M39, the Perseus Double Cluster, M31, M57, M42, and the Pleiades Cluster. No Paracorr or other coma corrector was used during any observation. Field conditions during the tests was generally in the area of Pickering 5 to 6 for Seeing, and Limiting magnitudes ranged from Magnitudes 4.0 to 4.5. The test location was suburban with medium light pollution, located about 15 miles west of Washington, D.C. in Vienna, Virginia.











Overall, the 24mm Hyperion proved to be a good performing wide field which drift testing results showed a 67.5 degree AFOV and 1.35 degrees of TFOV in the XT10i. However, I would not rate its off-axis performance up to the standard of a full premium such as a 24mm Panoptic or a Pentax XW. Having an older TeleVue 24mm Wide Field eyepiece on hand, I put the edge correction of the 24mm Hyperion on par with this eyepiece over a similar True Field of View (TFOV), however, the Hyperion showed much improved contrast and transmission compared to the TeleVue Wide Field. The substantial driving factors affecting the edge performance in the 24mm Hyperion were byproducts of coma from the Dob's fast optics, and field curvature possibly from the mirror as well. Centrally, when used in the fast Dob approximately 60%-65% of the Hyperion's Field of View (FOV) showed a nicely resolved star field. The outer 40% of the FOV through the eyepiece lacked pinpoint stars due to the observed coma and field curvature when used in with the fast optics of XT10i, progressing from showing mild coma and field curvature at 40% from edge to moderate-plus at the very edge. I was however able to correct the field curvature out to about the 75% from center region by selecting a focus between the two extremes of the curvature and letting my eyes accommodate the needed refocus. There was also some mild astigmatism noted in the far outer 20% of the FOV and very slight Chromatic Aberration showing on bright stars in the far outer 15% of the FOV. A graphical summary of how this eyepiece performed across its AFOV in the 10" f/4.7 Dob can be seen below.




Now, how did all these cold clinical performance details related to edge of field aberrations translate into the viewing experience? While charts and numerical details are helpful, they very often do not tell enough of a story and more can usually be gleaned from observation narratives rather than numbers and graphs. With that said, I will now turn to how it felt observing real celestial targets with the 24mm Hyperion.

I decided to turn first towards one of my favorite Fall evening objects, the Perseus Double Cluster (NGC884 and NGC869). Placing both clusters nicely centered in the FOV, the off-axis coma and field curvature through the XT10i did impact the hearts of each cluster. However, both were still minimal at the position of the hearts of each cluster and the field curvature could still be center focused for my eyes to easily fully compensate so the hearts of the Double Cluster appeared sharp and defined. The outer edges of each cluster, however, were not pinpoint, but this was not of significant impact given the relative dimness of these stars. So overall, while not what I would call outstanding tack sharp to the edge performance, still a rather acceptable showing for this eyepiece while in a fast Newtonian with no coma correcting device in the optical train.









Turning my attention to the very faint stars in both NGC 869 and later in M39, I quickly noticed the effects of improved transmission and/or contrast with the Hyperion compared to what the older TV 24mm Wide Field was delivering ? the Hyperion showed the fainter stars in these clusters to be brighter and more easily noticeable. Very faint stars in NGC 869 and M39, for example, were readily apparent and quite beautiful against a very dark bacground in the Hyperion whereas in the TV 24mm I had to strain to pick them up. Similarly, when I turned to M31 and M57, both of these targets also displayed themselves brighter and more vividly in the Hyperion -- the central core of M57 being darker with more faint stars in the region around it, and the central galactic bulge of M31 being larger, brighter, and more impressive. Turning to M42, the 24mm Hyperion's transmission and contrast performance presented itself exceedingly well. The depth, contrast, and extent of M42's nebulosity in the Hyperion was significantly better than what the TeleVue Wide Field was showing ? nebulosity was markedly brighter, nebula wisps extended further, course dark areas in and around the nebulosity were noticeably darker, the general background in the FOV was darker, and the fine moultiness within the nebula structure showed itself more prominently. In the TeleVue Wide Field by comparison, these structures were muted and very much more understated.

As previously mentioned, for the Double Cluster, the hearts of both NGC 884 and NGC 869 could be placed within the sweet zone of the 24mm Hyperion. With M39, having even dimmer stars, the sweet spot was perceived as being more than generous than the 60-65% on-axis area, with all its component stars swimming sharply defined through the FOV. But with the real acid test for the off-axis area being a very bright cluster, I slewed the scope over to the Pleiades Cluster to see what would happen. Basically, Pleiades proved more problematic as the XT10i'scoma in the outer 40% of the Hyperion's FOV presented itself very noticeably, easily standing out even in peripheral vision due to the brightness of these stars. Not a great showing with Pleiades for the 24mm Hyperion in a fast Dob with no coma corrector. So if you are sensitive to coma and observe with a fast Newtonian with no coma corrector, this Hyperion may sit on the edge as to whether you can tolerate the off-axis area.

On the upside relative to off-axis performance, for those people who are sensitive to barrel or pincushion distortion the 24mm Hyperion shows almost none. While scanning thru rich star fields, stars traced a pleasantly straight path. Placing the 24mm TeleVue Wide Field in the focuser, the same rich field scan at times produced an uneasy sensation in the stomach as stars whipped around curved paths off-axis. Similarly, when I observed the Moon in the TeleVue Wide Field I needed to be careful not to let it wander too near the edge as it would become elongated and appear to be sucked out of the FOV. With the Hyperion, the Moon kept its shape regardless of its location in the FOV. Turning briefly to a illuminated window frame on a house down the block also confirmed that even at the very edge of the field, straight structures maintained their shape and did not distort from any rectilinear distortions.

While observing the Moon, I must say that some really outstanding views were provided through the 24mm Hyperion. Observing the Moon while it was just shy of the half phase, it was crisp and etched from limb to limb in the Hyperion's field of view. Only when I positioned the Moon's limb at the very edge of the field stop did any softness in the image show itself. With the Moon off to the side in the FOV like this, approximately one quarter of its diameter looked soft. But given that the 24mm Hyperion was pumping 1.35 degrees true through the XT10i, Luna would never be in this location in the FOV under typical observing circumstances. So the Moon had plenty of Òswimming room" in this scope-eyepiece combination and proved to be quite an enjoyable eyepiece for Lunar observing with details across the entire Lunar surface presenting themselves as crisp and etched throughout the vast majority of the FOV.

As luck would have it while I was on the Moon, I also saw the occultation of the magnitude 6.75 star HP91273. So this was very nice luck watching the star pop out of view as it dipped below the dark side of the Moon. It also surprised me to see how bright and clear the star was in the FOV as it occulted not very far from the very brightly illuminated limb. With the Moon being so bright at nearly half phase, I was surprised that the background of space around the Moon was as dark as it showed through the Hyperion. Also, the dark side of the Moon was prominently brighter in the FOV compared to the background of open space. Again I did not expect there to be such a stark difference given the brightness of the nearly half phase and the resulting flood of light through the eyepiece. So the Baader coating technology, Phantom Coatings as they call them, made a very good showing. I also did a quick test for ghosting, flare, and reflections using the Moon. When I positioned the Moon out of the FOV in various positions at no time did any ghosting, reflections, or flare from this bright source occur ? a difficult test for any eyepiece.

Having just tested for reflections and flare with the Moon, it was time to run the same test for a bright star. Vega was chosen for this test. As Vega was positioned outside the FOV and drifted slowly into the FOV, a minor reflection was noted along the barrel inside the field stop. This reflection never entered the optical viewing field but remained very briefly as a short line of reflected light along a portion of the non-optical zone outside the optical FOV. Once Vega was about 2 star diameters inside the field stop the reflection vanished. Vega was the only star that showed this momentary reflection. Vega also showed a very minor amount of CA when it was positioned around 15% from the edge, but it was very slight and difficult to see. Seeing CA for the first time through the Hyperion with Vega, I went back to the Moon to see if there was any CA on the limb. Sure enough, if the Lunar limb was placed within 15% of the edge of the FOV, a very dim yellow or magenta line along the limb was just detectable, the color depending on which side of the FOV the limb was placed. Again, if you weren't looking for it you would probably not notice it since it was very subdued.

So overall, the 24mm Hyperion proved to be a very enjoyable and comfortable eyepiece to use. At no time was this eyepiece sensitive to eye placement, eye relief was extremely comfortable, and it displayed no barrel or pincushion distortions. While I do not wear glasses, I did grab a pair of drug store +1.5 diopter glasses and confirmed using these that one should still be able to view the entire AFOV with glasses. Using a fast Dob with no coma correction, the 24mm Hyperion showed spectacular views in a 60%-70% central sweet zone. While I would not class the edge correction of this eyepiece at the level of a 24mm Panoptic, for its price the 24mm Hyperion is probably one of the better bang-for-the-buck eyepieces available for semi-fast scopes.

While performance in a fast Newtonian proved good across a wide range of targets how would things change with other scopes and focal ratios? With this question in mind I decided to give a brief go with the Hyperion in a fast and slow Achromatic refractor. Placing the 24mm Hyperion in my Antares 6" f/6.5 refractor, stars fields were razor sharp in the central 80% of the FOV ? excellent performance. In the 80mm f/11 TMB/Burgess Planet Hunter refractor stars were sharp even a little further out, to about the 90% from center mark. In fact, in the f/11 instrument the entire star field was etched so sharply, and the edge distortions so minimal, that I would characterize the view as simply stunning. When I turned this 80mm f/11 scope to the Pleiades Cluster, which did not show well in the XT10i with the 24mm Hyperion, I ended up placing all the other eyepieces I had out with me back into the case, brought up a more comfortable chair, and sat down to enjoy a good long observation of this wonderful cluster. The view of Pleiades through the 24mm Hyperion was so good with the 80mm Planet Hunter, it was simply mesmerizing over the entire 1.72 degrees of TFOV providing a very memorable view to say the least.

Conclusion

Across all scopes the 24mm Hyperion proved itself to be a very enjoyable eyepiece to handle and use in the field, showing no sensitivity to eye placement while viewing, and providing very high contrast and high transmission views with extremely comfortable eye relief. I would recommend this eyepiece for scopes at f/5 focal ratios or slower. If you are faster than f/5, a coma correcting device would be recommended, but tolerable without if you are not overly sensitive to coma. I would also definitely recommend this eyepiece, even for fast scopes as an alternate to top shelf premiums if one cannot afford the extra costs those eyepieces command. In all my tests and use, the 24mm Hyperion proved to be a very enjoyable and capable performer at a very down-to-earth price, and for longer focal length instruments it shines as a real gem.