What Is A Kellner Eyepiece? (Explained!)

The Kellner eyepiece was designed in 1849 and has been a mainstay in the optics market ever since. It is considered to be the best of the beginner lenses. If you’re new to telescopes and want to bring stargazing into your hobby umbrella, you can’t do much better than to start with a Kellner.

A Kellner eyepiece is a three-lense system with two locked together (a doublet) and a single lens as well. The original design was intended to create a clearer image by eliminating ‘aberrations’ in the field of view so that the viewer could enjoy a clearer image with little to distract.

How Does a Kellner Eyepiece Work?

The Kellner is a simplistic design, which owes much to its age since it hasn’t changed in over a century and a half. The doublet combined with the single lens is a design that eliminates false colors and gives you a more precise view of the heavens, with full color in a field of view from 30° to 50°.

It’s known as an achromatic eyepiece because it doesn’t disassemble light into each of the colors of the spectrum. The colors in the light that passes through a Kellner are true to life colors.

The Kellner was certainly a massive advantage for its time but its time is long past and technology has advanced to the point where the Kellner is now relegated to the very best of what you would expect from beginner telescope eyepieces.

Who Created the First Kellner Eyepiece?

Carl Kellner invented the Kellner eyepiece in 1849 while still in his early 20s. He didn’t live long, dying of tuberculosis just shy of his 30th birthday. However, his Kellner eyepiece was a lasting contribution to the world of optics.

Six years prior to his death, he founded Optisches Institut, which was a company that specialized in the improvement and production of eyepieces both for use in telescopes and for microscopes.

Back then, viewing the planets and stars through a telescope was often an irritating experience because you had to deal with distortions such as ghosting and light aberrations that interrupted the viewing experience.

Kellner meant to devise a lens that was free of that and he did so, in the six short years prior to his death. Long afterward, the company he founded became the Leitz Company, which still manufactures lenses for various optical instruments, including Leica Cameras. 

Are Kellner Eyepieces Good for Viewing Planets?

Kellner eyepieces are considered to be the best of the beginner telescope eyepieces and they are perfectly fine for viewing inner planets. It may be a more difficult prospect trying to view outer planets with Jupiter as an exception because of how bright it can be.

If you want a more detailed view of gas giants then you will probably have to upgrade your eyepiece but with a Kellner, you will be able to see the ring of Saturn and make out enough of Jupiter to see the red hurricane that perpetually dots its surface, along with Jupiter’s four largest moons.

Mars is a difficult prospect on any given day, depending on where it is and how the light is reflected from the. The same could be said for Venus.

However, Venus is a fascinating planet to watch using a Kellner, so long as you mount a moon filter on your eyepiece the Kellner eyepiece should work quite well for this task.

Venus reflects a large amount of light from the sun and without a moon filter or something similar, it will appear as a giant, white ball in your scope, regardless of your eyepiece.

Pros of Kellner Eyepieces

Kellner eyepieces are not considered to be the best eyepieces in the world, however, they also don’t have much in the way of cons either. The idea behind the Kellner eyepiece, showing colors as they truly are, without degradation, made it an eyepiece worthy of lasting 173 years.

Because of its age, it’s a simpler variation of all of the eyepieces out there, and it’s also one of the least expensive.

When you’re 173 years old, people don’t have to pay as much for your services, as opposed to Nagler, Delos, or Ethos eyepieces, which are modern and highly expensive.

This achromatic lens is very as the Plossi, which is considered to be a slightly beginner level eyepiece than the Kellner.

It also has a moderate eye relief and although there are a few voices out there that define these eyepieces as having a short eye relief, those are merely personal opinions because eye relief is highly affected by external factors.

Cons of Kellner Eyepieces

Kellner eyepieces are limited by their age and by the fact that the technology that goes into eyepieces long ago surpassed the Kellner.

It only has a moderate eye relief and, depending on the individual, may not be enough for some. It also doesn’t have a very wide field of view, which tends to expand with the more lenses that are added.

There are also some persistent color aberrations that can still creep in, regardless of the fact that the Kellner was designed to eliminate them and there are better lenses today that all but eliminate it.

Summary

Overall, Kellner eyepieces are excellent, beginner eyepieces for someone that is just dipping their toes into the world of stargazing.

While it isn’t the end all be all of the telescope eyepieces, a good Kellner will be more than enough to draw you in and get you hooked on this hobby.

References

A Guide to Eyepieces Part 2

Retrieved from: https://www.saguaroastro.org/a-guide-to-eyepieces-part-2/

Kellner vs Plossl Eyepieces (Pros And Cons)

Retrieved from: https://scopethegalaxy.com/kellner-vs-plossl-eyepieces/