15 replies to this topic

[Takuan]

Last weekend I was in a dark place with my dob and Linear binoviewer. In the city the Baader H. Zoom are my favorites with the combo 6"Mak/ Maxbright BV (Moon, Planets and Double Stars) and I took them for the first time under a dark sky with the dob. The surprise, for me, was to verify that simple 20 mm Sterling plossl gave a better image in Deep Sky than the zooms at the same FL. The difference, obviously, was not huge, but clearly visible in my eyes.

Historically I have read testimonies from Deep Sky observers who prefer eyepieces with few elements (Plossl and Orthos) than newer designs with more Afov. The truth is that I never thought that this difference was as visible in oculars of, in principle, high quality as the Baader.

So the questions would be, what is your experience about it? Is it necessary to go to the most expensive brands and models (Televue?) To make this difference less marked or non -existent?
Is there a difference between 4 and 6 elements, for example? (I think about 60⁰ Afov types vs. a plossl).

Edit: I have also observed differences between 20 mm S. Plossl and 18 mm Uff in Deep Sky (in favor of the first).

Edited by Takuan, 05 April 2025 - 04:18 AM.

[Astrojensen]

 

So the questions would be, what is your experience about it?

It is real.

 

 

Is it necessary to go to the most expensive brands and models (Televue?) To make this difference less marked or non -existent?

Yes. 

 

 

Is there a difference between 4 and 6 elements, for example? (I think about 60⁰ Afov types vs. a plossl).

That depends on the eyepieces. If you compare very high-end 4-element eyepieces, such as Takahashi TPL or Zeiss Abbe Ortho, with a budget 6-element, or an older design, then the difference can be quite obvious. Less so, if the 6-element eyepieces are high-end ones. 

 

 

Clear skies!

Thomas, Denmark

[Jay_Reynolds_Freeman]

In my experience, the eyepieces that deliver the highest-contrast images all have few air/glass interfaces -- typically four. Note, that that is not to say that every eyepiece with just four air/glass interfaces gives high contrast. I believe the reasons are that polishing is not always perfect -- and imperfectly polished surfaces scatter light, and furthermore that less-than-perfectly applied coatings may have rough surfaces, which also scatter light.

 

It is also true that no low-reflection coating transmits 100 percent of incident light. With a lot of air/glass interfaces, the loss might be noticeable: Thus if the coatings transmit ninety-nine percent and reflect one percent, transmission through an eyepiece with ten coated air/glass interfaces would be only about 90 percent (actually, 0.99 to the tenth power, which is 0.904...). That is not much, but every photon that is reflected back toward the sky has an additional chance to cause problems by again being reflected back toward the field of view, now out of focus, by one of those coatings. Take the ten air/glass interface eyepiece: Depending on which surface it is that reflects a photon back toward the sky, that photon will have, on the average, about five more chances to get redirected again by a 99 percent coating. Thus about five percent of the ten percent of photons that are reflected back toward the sky will return to cause glare in the image. That is half a percent of the incoming photons, which doesn't sound like much, but if you are looking for small-scale low-contrast detail on a bright lunar or planetary surface, or trying to spot the faint companion of a bright double star, the extra scatter from the bright stuff in the field of view might make a difference.

 

One quick way to evaluate coating quality is to look straight on into the ends of an eyepiece with clean lenses. If you can see any lens surfaces, the coatings are second-rate or worse. Looking through a well-coated lens should be like looking into a space warp of some kind -- the light appears distorted but there is no visible cause. Thus if you encounter a Maksutov or Schmidt-Cassegrain corrector that is well coated, it will be invisible -- the secondary will appear to be suspended in space, as if by anti-gravity.)

 

Another possible problem might be poor blackening of the edges of the various eyepiece lenses -- those surfaces are generally ground, and can scatter light. The more surfaces, and the thicker the lenses, the more scattering.

 

The eyepieces that I have personally used that seem to have the best contrast -- the lowest scattered light -- are classic Brandons and Pentax SMC-ED orthoscopics, all of which have only four air/glass interfaces.

 

Your mileage may well vary, and I expect that there are fancy eyepieces (with more than four air/glass interfaces) that do well for contrast, I just don't know which ones they are, and there are a lot of eyepiece types that I have not tried.

 

 

Clear sky ...

Edited by Jay_Reynolds_Freeman, 05 April 2025 - 06:53 AM.

[mrowlands]

Someone can correct me if I'm wrong, but although the Baader Zoom is excellent for what it is, I think a very high-end 6 (or more) element eyepiece will be better.

 

Mike R.

[EsaT]

... Baader H. Zoom are my favorites with the combo 6"Mak/ Maxbright BV (Moon, Planets and Double Stars) and I took them for the first time under a dark sky with the dob.

...in principle, high quality as the Baader.

Morpheus is Baader's high quality line, not Hyperion.

And zoom eyepiece is always harder to make good than fixed.

Dobson being f/5 with wide fast converging cone of light is also lot more demanding for eyepiece quality than f/12 to f/15 Maksutovs...

 

I have APM 7.7-15.4mm zoom rated higher than Hyperion Zoom and getting 12.5mm Morpheus made it feel plain mediocre.

Both for M13 with clearly sharper and more contrasty stars and Moon's details and especially fine details.

Sure it's possible my zoom sample is below average individual, but propability is for it being average and expecting it to go toe to toe against high quality eyepiece simply being too much.

[snakehelah]

I'm quite new to the hobby so take it with a grain of salt, but from testing some eyepieces the last few weeks I felt like the ES 11mm 82 and ES 14mm 100 outperformed the Baader zoom in pretty much everything.

The only advantage the zoom had going for it was obviously it's convenience, but I only felt it was useful with the bundled barlow, and that is adding even more elements to the mix. At that point I started feeling like it's just an overcomplicated high power piece. And it also felt like the barlow introduced its own set of issues.

Ultimately I felt like a dedicated high power (still deciding, maybe 6.7mm or 4.7mm) eyepiece would make more sense to me, which is why I opted to RoW return the baader zoom bundle. I'd probably appreciate the baader zoom but the price point just breaks it for me, you can kind of get 2 decent eyepieces for the price of the zoom+barlow bundle.

I do have some stock 25mm and 10mm plossls that came with the dob to compare it with and of course the ES eyepieces beat those in everything but surprisingly the plossls still offered good views and I do have a gut feeling like there's some truth that less layers might help with clarity. 

The drawback of plossls ultimately seems the be FOV but I'd be curious to hear from seasoned observers as to how their plossls compare to the wide FOV eyepieces for clarity for planets or DSO.

Edited by snakehelah, 07 April 2025 - 04:23 PM.

[Procyon]

Plossls work great on planets with binoviewers! For monoviewing with a dobsonian scope, you'll be much better off with similar eyepiece types that you currently own. Or ones with more AFOV so you don't have to chase the planet every few seconds.

You seem to like the eyepieces you have so build your set with those. You currently have magnifications of 45x, 85x, and 110x. I'd want something around 150x-180x and 210x-240x next. A 7mm Pentax XW or a 7mm XWA would give you 170x. A 5mm Pentax XW would give you 240x and depending where you live, it may suit you fine for high magnification on planets. A 5.5mm ES 100 (220x) is another option. And like you said the 6.7mm and 4.7mm ES 82's are other options also. (180x and 255x).

Give, sell or throw away the original plossls that came with the scope. You are correct about zooms, practical but not that great. Unless you buy the ones that cost 1k. Just my honest and humble opinion.

Research everything and also take a look at Don's eyepiece list in the eyepiece section stickies.

Edited by Procyon, 08 April 2025 - 06:10 AM.

[Mike W]

Last weekend I was in a dark place with my dob and Linear binoviewer. In the city the Baader H. Zoom are my favorites with the combo 6"Mak/ Maxbright BV (Moon, Planets and Double Stars) and I took them for the first time under a dark sky with the dob. The surprise, for me, was to verify that simple 20 mm Sterling plossl gave a better image in Deep Sky than the zooms at the same FL. The difference, obviously, was not huge, but clearly visible in my eyes.

Historically I have read testimonies from Deep Sky observers who prefer eyepieces with few elements (Plossl and Orthos) than newer designs with more Afov. The truth is that I never thought that this difference was as visible in oculars of, in principle, high quality as the Baader.

So the questions would be, what is your experience about it? Is it necessary to go to the most expensive brands and models (Televue?) To make this difference less marked or non -existent?
Is there a difference between 4 and 6 elements, for example? (I think about 60⁰ Afov types vs. a plossl).

Edit: I have also observed differences between 20 mm S. Plossl and 18 mm Uff in Deep Sky (in favor of the first).

With modern designs and coatings nothing to worry about. Only a fringe few would look through a soda straw. If you are worried about it get a TV Delite, minimal no. of elements, good eye relief, high transmission and contrast.

[SeattleScott]

Someone can correct me if I'm wrong, but although the Baader Zoom is excellent for what it is, I think a very high-end 6 (or more) element eyepiece will be better.

 

Mike R.

I can attest to this, along with a couple of my stargazing buddies.

 

The Sterling Plossl is not only minimal glass, but it is also a high quality eyepiece. Zooms simply can't be optimized for the whole range. So the zoom is high quality also, but it is handicapped by being a zoom, and a more complex eyepiece. Simply being a zoom is probably the biggest factor. 

 

Zooms are about convenience, or cost effectiveness (cover multiple focal lengths with a single eyepiece, although the price of the BHZ can make it questionable in terms of cost effectiveness). Zooms are not about maximum planetary contrast, or wide AFOV (typically). 

 

The BHZ and APM Superzoom are both very good for zooms, but bench tests don't put them on par with similarly priced fixed eyepieces. Which makes sense. I mean, if the BHZ and Superzoom provided views just as good as Delos or Morpheus, and covered multiple focal lengths, who on Earth would buy Delos and Morpheus?

 

Now the Leica might go toe to toe with Delos and Morpheus, in contrast and AFOV. While covering multiple focal lengths. But then, the Leica costs about as much as three of them. 

[CrazyPanda]

Someone can correct me if I'm wrong, but although the Baader Zoom is excellent for what it is, I think a very high-end 6 (or more) element eyepiece will be better.

 

Mike R.

Yes. I briefly owned the BHZ. It's about par for the course when you compare it to various mid-grade eyepieces in terms of sharpness and contrast.

 

When you compare it to DeLites, Delos, Pentax XWs etc, it isn't quite up to the same level of sharpness and contrast. It's close, but if you have a good objective and reasonably steady skies, you'll see the difference.

 

The main advantage of the BHZ is the same one you'll find in every zoom - getting the exact right magnification or balance of magnification and view brightness for the object and the conditions.

[Jon Isaacs]

Yes. I briefly owned the BHZ. It's about par for the course when you compare it to various mid-grade eyepieces in terms of sharpness and contrast.

 

When you compare it to DeLites, Delos, Pentax XWs etc, it isn't quite up to the same level of sharpness and contrast. It's close, but if you have a good objective and reasonably steady skies, you'll see the difference.

 

The main advantage of the BHZ is the same one you'll find in every zoom - getting the exact right magnification or balance of magnification and view brightness for the object and the conditions.

 

In theory, I still own a Baader zoom but I loaned it to a friend nearly 4 years ago and I haven't felt a need to ask for it back.  He likes it and uses it.  I bought it to try to fill the gap between the 13mm and 8 mm Ethos.. In the end, I just found a used 10mm Ethos.  The Baader zoom is a pretty good eyepiece if you figure it replaces maybe three $100 eyepieices.  

 

That depends on the eyepieces. If you compare very high-end 4-element eyepieces, such as Takahashi TPL or Zeiss Abbe Ortho, with a budget 6-element, or an older design, then the difference can be quite obvious. Less so, if the 6-element eyepieces are high-end ones.

 

 

It also depends on the telescope, the mount, the object, the observer..  In the long list of importances, the eyepiece is pretty far down the list.  It is easier to compare eyepieces that it is to compare telescopes but the telescope is far more important than the eyepiece in determining what is seen and not seen.  

 

Eyepieces are the interface between the telescope and the observer.  A comfortable view is an important aspect of making difficult observations.  Does the mount track?  What's the focal ratio of the scope, what are the inherent aberrations? What are the inherent limitations?  Is the scope a reflector or SCT with reflectivity losses, scatter, potentially a large CO, is there enough eye relief?  Is the off-axis correction decent?  

 

In my 22 inch, 600x requires a 4.1 mm eyepiece.  A 4 element eyepiece is going to have about 3 mm of eye relief. If the AFoV is 40 degrees, the TFoV is going to be 4 arc-minutes, manual tracking, that's very difficult.  On the other hand, the scope has very good optics and an 16% CO, it's not robbing much contrast from the view.  

 

Somewhere there are some measurements on the transmission of various eyepieces.  The Zeiss Orthos are quite good but the type 6 Naglers were not far behind, 2-3% if I remember correctly.  

 

"It is not usually made clear, that these elements, objective and eyepiece, are by no means comparable in importance. The astronomer's hopes are almost wholly tied to the size and quality of the objective. The objective of even the smallest telescope, because of its larger dimensions, the severe optical requirements it must meet, and the difficulty of its construction, completely overshadows the eyepiece."

 

- "How to Make a Telescope," by Jean Texereau, Page 1, Paragraph 2. "

 

Jon

[davidgmd]

Keep in mind that under controlled conditions most people can't detect differences in brightness until they reach 8% or more. No doubt there are exceptions.

I imagine some of the differences attributed to eyepieces are actually due to differences in front of or behind the eyepiece.

[havasman]

Compare again with a pair of 13T6 Naglers substituting for the zooms. Results will likely differ.

 

Careful review of the most in-depth analysis of highest end minimal glass eyepieces' value in threshold galaxy observing (Alvin Huey's) shows the very well equipped, extremely experienced observer finds the advantages of minimal glass are not in play below 24 or 26" apertures in premium Dobs and ramp up sharply in apertures > 30". Comparisons were recorded up to 48" aperture. Resolution is simply greater at those apertures and finer distinctions are available. Reference: faintfuzzies.com

[turtle86]

In theory, I still own a Baader zoom but I loaned it to a friend nearly 4 years ago and I haven't felt a need to ask for it back.  He likes it and uses it.  I bought it to try to fill the gap between the 13mm and 8 mm Ethos.. In the end, I just found a used 10mm Ethos.  The Baader zoom is a pretty good eyepiece if you figure it replaces maybe three $100 eyepieices.  

 

 

It also depends on the telescope, the mount, the object, the observer..  In the long list of importances, the eyepiece is pretty far down the list.  It is easier to compare eyepieces that it is to compare telescopes but the telescope is far more important than the eyepiece in determining what is seen and not seen.  

 

Eyepieces are the interface between the telescope and the observer.  A comfortable view is an important aspect of making difficult observations.  Does the mount track?  What's the focal ratio of the scope, what are the inherent aberrations? What are the inherent limitations?  Is the scope a reflector or SCT with reflectivity losses, scatter, potentially a large CO, is there enough eye relief?  Is the off-axis correction decent?  

 

In my 22 inch, 600x requires a 4.1 mm eyepiece.  A 4 element eyepiece is going to have about 3 mm of eye relief. If the AFoV is 40 degrees, the TFoV is going to be 4 arc-minutes, manual tracking, that's very difficult.  On the other hand, the scope has very good optics and an 16% CO, it's not robbing much contrast from the view.  

 

Somewhere there are some measurements on the transmission of various eyepieces.  The Zeiss Orthos are quite good but the type 6 Naglers were not far behind, 2-3% if I remember correctly.  

 

"It is not usually made clear, that these elements, objective and eyepiece, are by no means comparable in importance. The astronomer's hopes are almost wholly tied to the size and quality of the objective. The objective of even the smallest telescope, because of its larger dimensions, the severe optical requirements it must meet, and the difficulty of its construction, completely overshadows the eyepiece."

 

- "How to Make a Telescope," by Jean Texereau, Page 1, Paragraph 2. "

 

Jon

 

Really good low glass count eyepieces like ZAO II's go a little deeper than Naglers, but I've found that the difference is very slight at best, at least in my 18".  Maybe a bigger scope would show more of a difference.  To me, the quality of the optics, quality of the viewing conditions, and experience of the observer are more important considerations.  And as you say, comfort is very important, especially when making difficult observations.

[39.1N84.5W]

Number of elements in an eyepiece is over stated and nearly irrelevant. There are myriad other factors that take priority, as have been posted.

[betacygni]

I’ll start by saying the Sterling plossls are actually very very good eyepieces. They were an absurdly good value in their day (think I got mine for $30 each new if I recall correctly), and objectively great performers even ignoring price. I sold my 24mm panoptic pairs (twice actually, second guessed myself a few years later) in favor of the Sterlings costing many multiples less. I don’t do a lot of deep sky observing where I’d confidently give an opinion, but my Sterlings were only dethroned by my current Brandons and my latest crush, the Tak TPLs which are simply magic.

Also, with the Linears the 20mm Sterling are maxing out your binoviewer’s clear aperture. No need for more complex AFOV eyepieces, you won’t gain any TFOV by doing so, since they’d vignette.

Edited by betacygni, 12 April 2025 - 09:52 PM.