Plossl and Kellner are the two most popular eyepiece designs among the rising stargazers. People often compare them side by side. There’s a debate on which one of these eyepiece designs is better.
So, what are the differences between Plossl VS Kellner?
Between Plossl and Kellner eyepieces, Plossl would be superior. Plossl has 4 lenses in symmetric order whereas Kellner eyepiece has 3 lenses. Plossl have a better FOV than Kellner. Both of the eyepiece design falls behind in eye relief. Even so, Plossl is comparatively better in this aspect.
That would be the trailer of our today’s conversation. If you’re curious to know more, keep reading with us till the end.
Let’s get more into the details!
Short Comparison Between Plossl vs Kellner
Before we move on to serious debates, let’s see a short preview. The table below gives a short comparison between Plossl vs Kellner.
Need more detailed explanations? Then join us in the next segment.
Detailed Comparison Between Plossl vs Kellner
If you’re new to stargazing almost everyone will suggest you Plossl or Kelnner eyepieces. Because that’s how much popular it is among the new astronomers.
Pretty sure you’d want to buy the better one between both. So a detailed comparison is necessary.
Here we have talked about the main differences between both eyepieces. We’ve also declared a winner. Let’s go through each of these aspects to find out the reason why.
Design Of The Eyepieces
Plossl eyepieces have four lenses whereas Kellner eyepieces have only three. The lenses of Plossl eyepieces come in two groups. It has two concave and two convex lens.
Where’s Kellner eyepiece has two convex and one concave lens connected together. Although Plossl and Kellner both are achromatic lenses, they are designed differently.
Plossl eyepieces have a set of doublets that are symmetrical to each other. Because both of the lenses are identical it’s called symmetrical eyepieces.
The lens of Kellner eyepieces is not symmetric. Also, Kellner eyepieces have an issue with internal reflection but Plossl eyepieces don’t.
The super Plossl contains two more lenses that face each other parallelly. It makes the eyepiece narrower in angle but more precise in details. That’s one of the differences between Plossl & super Plossl eyepieces.
Although both of the eyepieces are good, Plossl is definitely better in comparison.
Winner: Plossl.
Field Of View(FOV)
Field view is a very important aspect of an eyepiece. It determines how much of the sky will be visible through the lens.
The Plossl eyepiece has an average field view of 50° to 56°. While the Klenner eyepiece has a field view of 30° to 50°. In comparison between all the sizes, Plossl has a greater FOV than Kellner eyepieces.
Kellner’s narrow FOV is handy in some special situations. It highlights a dimmer object well when it’s beside a bright object. The narrow FOV excludes the light from the brighter object.
But that’s just one scenario. Plossl’s wider FOV gives you more options to observe the cosmic objects. If you’re wondering what makes Plossl special, this is one of the few reasons.
Plossl also has fewer optical errors and provides brighter colors than Kellner’s. So if you need either of the two I would suggest you go for Plossl.
Winner: Plossl.
Eye Relief
Eye relief is another important factor when choosing an eyepiece. Especially for those who wear glasses. Eye relief determines the distance from where a component can be seen at full view.
Plossl and Kellner eyepieces under 12mm focal length have poor eye relief. Plossl eyepieces of 0.695” have the worst eye relief between other Plossl eyepieces.
The same goes for Kellner as well. But Plossl 1.25” and 2” have better eye relief than same-sized Kellner’s. Also for bigger focal length eyepieces the eye relief problem is reduced.
It is even more so in the Kellner eyepieces. This is due to the restriction of 70-80% of the telescope’s focal length.
So, what is the focal length of eyepieces?
The focal length is the distance between the lens and the light’s crossing point. The light that enters through the lens meets at one point on the focal plane. As a result, an image is created there. And we get an angler view of the object. The higher the focal point the greater the magnification is.
Plossl have greater eye relief at bigger focal length distances. But at the same focal length, Kellner eyepieces have smaller eye relief.
If you wear glasses you can definitely look for some better options for eyepieces. How about going for Omegon Eyepiece Ortho 10.5 mm? They have greater eye relief than Plossls and definitely more than Kellner’s.
In a comparison of eye relief, Plossls are better than Kellner’s. Plossl has an eye relief of 20mm at 28mm focal length. Where’s Kellner has an eye relief of 13mm at the same focal length.
So for better eye relief, the choice should be Plossl. Even more so if you wear glasses.
Winner: Plossl.
Cost
When it comes to price, Plossl is more expensive than Kellner eyepieces. And why wouldn’t it be? Plossl eyepieces give better performance, have more features, and have a better design than Kellner.
Although you may find the 0.965” Plossl at a cheaper rate, they’re not worth it. Plus you’d need an adapter to use it with most telescopes.
Plossl eyepieces cost more than Kellner’s. This is due to Plossl’s round performance. Also manufacturing Plossl eyepieces cost more than Kellner.
In fact manufacturing, Kellner eyepieces are easier and cheap. Some manufacturers even use low-end glass to make the lens. Such low-end Kellner eyepieces give the worst performance.
But the high range of Plossl eyepiece might be a problem for buyers. If you’re looking for a more budget-friendly option then give SVBONY Eyepieces a shot.
Maybe you’ll get your desired Plossl eyepiece at a cheaper rate here.
Even though Plossl eyepieces are pricier than Kellner, it’s more cost-effective. Also, it’s the best investment for the long run.
Winner: Plossl because every penny is worth it.
FAQs
Is Ramsden eyepiece design superior to Kellner?
No, in terms of design Kellner is better than Ramsden. Kellner has better features and fewer shortcomings than Ramsden. The main problem with Kellner is the inner reflection. That too is solved with anti-reflection coating.
Are Kellner eyepieces related to Ramsden eyepieces?
Yes, Kellner eyepieces are an improved version of Ramsden eyepieces. The revised version has a double-eye lens connected together. It also has a higher eyepoint and better FOV.
What eyepieces are best for watching deep-sky objects?
Plossl is the best choice for watching deep sky objects. You’ll be able to see nebula and clusters pretty clearly with it. Keeping a 15 and 25mm Plossl eyepiece in your collection would be great.
Endnote
That was all from us about Plossl vs Kellner. Hopefully, you’ve got the answer to why Plossl is better between both.
But that doesn’t mean Kellner is bad. It is also favorable to many. So the best way to decide is to gain first-hand experience of using both.
That’s it for today. See you next time!
