Eyepiece Shootout

Three top shelf eyepieces compared side by side.

I’ve come a long way from that red tubed K-Mart telescope my wife bought me one Christmas years ago when we were dating (um… 35ish years now – gulp). Slowly, my gear has progressed, my tastes matured, and experience started costing me more and more money. I’d never spent more than $100 on an eyepiece before, and then I won my first Televue Nagler eyepiece at the Winter Star Party in 2003, and it turned my little case of Plossels into trash when I looked through it on my LX-200. Each year I’d scrape together some cash and I’d buy a new one to add to my collection that February. Today I have a complete set, and I am quite proud of them. They are killer on my fine refactors. Somewhere along my journey, I turned into an imager, but I still like to do visual astronomy, and I’m even active in the local club and do some outreach programs myself.

I always thought Naglers were the best of the best, but a few friends have told me that I should try a few other premium models. The Televue Ethos line for example, and also Pentax was known for making exceptional glass. I had no idea Pentax even made telescope eyepieces. A vendor friend who now works at Pentax loaned me a 20mm XW series eyepiece. He offered to let me give it a try and see how it compared to my beloved Naglers. I also recently came into the possession of a Takahashi telescope that came with a 24mm eyepiece. I found myself with Nagler, Takahashi, and Pentax eyepieces all at the same time. This sounded like a golden opportunity for a shoot out!

Typical configuration for lunar observing at my favorite outreach location.

Whenever I run into someone who says they can’t tell the difference between premium optics and the more budget gear, I know they haven’t actually tried them both. Not really, or not under good testing conditions. You can tell, and it’s not that hard. When you get to the upper end though, the difference between the premium brands (and this goes for just about everything) get’s finer and more difficult to discern from a casual inspection. Any of these three eyepieces are going to blow you away when compared to the eyepieces that came with your mass produced brand telescopes. I’m not saying these are bad scopes either, but the best telescopes in the world are hampered by the quality of the eyepieces. Of course, you can easily spend more on your eyepiece collection than the scope itself, and so it’s no wonder that the eyepieces are not the central value when you buy yourself a telescope (most of the time).

Back to the task at hand, side by side, these top choices are pretty neck and neck and I can tell you it takes a very discerning eye to tell the difference. I’ll tell you in advance now, if you have any of these models, don’t get rid of them, and you will be happy with any of these three. I’ll also confess that while I do have considerable expertise when it comes to astrophotography, I am a pretty average Joe when it comes to visual. I know enough to be dangerous, and by no means do I consider myself an expert here. Never-the-less, I can tell you what I saw and it might help you with future purchase  decisions, or just make you feel better about what you have. Again, if you have any of these three brands, you can justifiably feel great.

Okay, so the night of the shoot out was during one of my Coffee & Cosmos events. We were looking at the first quarter Moon with a Sky-Watcher Mak-Cass. The Moon is my favorite visual target, and it is merciless when it comes to optical quality. I spent the evening swapping between the Pentax XW 20, the Takahashi LE 24mm, and a Nagler 20mm type 2 (I also compared with a Nagler 13mm type 5, but it was a much closer view, and I wasn’t sure how fair it would be).

For the first 10 minutes I could not see any difference in quality between the three oculars. The lunar details were crisp and well rendered. There was no ghosting or glare either, and I felt as if I were in orbit above the moon. In isolation, any of these three were the best eyepieces I’ve ever looked through.

I wasn’t sure what to look for really. The lunar terminator was glorious with all three eyepieces. The Pentax was noticeably the wider of the three (thus the WX moniker) and I had to tilt my head to see everything. It was like a peep hole out the bottom of an orbiting space ship. Quite lovely, and I really could see no difference initially in terms of overall image quality.

I also repeated this experiment with a quality refractor from my back yard.

Then, suddenly, two neurons in my visual processing center connected. The Pentax and the Takahashi eyepieces yielded the most creamy white neutral image of the Moon. The Nagler was just a twinge warmer, or more yellow. Took forever to notice it, but again once you do, you can’t unnotice it. In the absense of the other two eyepieces I’d have never said… my, that looks a tad yellow don’t you think? It always seemed quite white and clear before. I never before and I still don’t find this slight yellow cast objectionable because it really is at the edge of perception and you really have to have something to compare it to in order to detect it. On any given night with only my box of Naglers it’s never going to be an issue. In fact I repeated this experiment at home using one of my Esprit refractors on the Moon. Using the Nagler, I could not see the warm bias in the slightest… until I popped in one of the other two eyepieces and compared it immediately. It’s like two television sets in a department store next to each other with slightly different color settings. If they weren’t right next to each other, you’d never know.

The next difference was along the lunar limb. I’ve compared the Nagler to so many lesser eyepieces that had a green or violet fringe along the lunar limb that to me the Nagler had no fringe at all. It was clean. I learned here a new meaning of the word clean. There is actually a small green tinge to the lunar limb. Almost imperceptible, and again in the absense of eypeices that render nothing there at all, I could not detect it. Now however… I could not NOT see it. Razor thin and ghostly… and again not objectionable, but if you look for it, it’s there. If it where a photograph, it would be a tenth of a pixel wide! <sic>

Now, the Takahashi and Pentax are tied. Both render a sharp view, both have NOTHING along the lunar limb. The Pentax might edge out the Tak because it has such a wide field of view. Again, scrutiny… in imaging we call this pixel peeping.

In the Pentax, the center is excellent, and as you wander out to the edges, it’s also very sharp, and I had no complaints. Only after switching back and forth did I notice something subtle again. The Pentax is quite wide, and this is a wonderful feature. The cost is the slightest, slightest loss of sharpness away from the center.  Out away from the center, the image is sharper in the Takahashi than with the Pentax. Tiny details on the surface are popping out in the Takahashi that are just not as well defined in the Pentax, or the Nagler (the Nagler Type 2 was also pretty wide, and similar across the field in sharpness to the Pentax). These are the smallest features, and I’m talking about surface texture here, not craters and rilles, those all look equivalently sharp. But the tiniest surface… fingerprints… those were apparent in the Takahashi more so than the Pentax or Nagler.

Now, it’s a tough call because it was HARD to see the sharpness difference, and only by doing this side by side. The Pentax however was much wider… and there is something to be said for that as well. I remember this feeling the first time I looked through my 31mm Nagler type 5… in comparison to my Plossels. Even if the Plossels had been slight sharper (which they weren’t), I still would have preferred the Nagler’s field of view.

So, I’ll call the Takahashi and the Pentax somewhat tied in this regard. Do you want that last 3% of sharpness at the edges, or do you want a portal into outer space experience? I should mention here too that the Nagler also provided a pretty wide field, but falls behind on the technicalities of being slightly off on color, and having the tiniest color along the brutal naked edge of the Moon. Never-the-less, I gave away most of my original eyepieces some time ago, and am still quite happy with my Naglers. We are down to the nitty gritty here, and the differences are pretty small. Only if I were starting over, might I make some different choices.

Summary

The Pentax has a wide field of view like the Nagler, but has better color fidelity. The Takahashi beat them both in terms of sharpness, but only just slightly, and with a much smaller apparent field of view. To be fair, my Nagler’s are now two generations out of date, and with both Ethos and DeLites now on the market the design has improved and I don’t have one of them to compare. Judging by their prices, I’d expect them to be more on a par with the Takahashi or Pentax eyepieces.

I am sorry to have to return my loaner Pentax so soon and maybe I’ll pick one up next NEAF when I’m on my next astro-shopping spree. However,  you should not expect to see my collection of Naglers on Astromart anytime soon. 😉

Clear skies,
Richard

 

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