26 replies to this topic

[25585]

I have seen reactions, some valid, others less so, on posts and/with reviews of eyepieces based on the telescopes used in testing them, focal length & ratio, aperture, type etc. 

 

So which scopes types & properties most validate eyepiece tests for you? Do you dismiss certain scopes types, look for all-rounders (eps & scopes), or are you only looking for what you use and want to own?

 

 

[MitchAlsup]

What I can tell you is that the wavefront matters.

 

At one point in time I had a 6" AP APO, a 11" SCT, and a 20" DOB, and a set of ZAO (1) orthos. So, I decided

to spend a night using these optics with those optics and see what I could <ahem> see. The chosen night was

perfect for a 6" aperture, pretty good for a 11" aperture and fairly ho-hum for a 20" aperture, so bear this in mind.

I also had (i.e., borrowed) a set of University Orthos from a friend, and had my own set of Naglers (T1 and T2);

also bear in mind this was done in the early 1990s.

 

The difference between the ZAOs and the UOs were clear and easy to see in the 6" AP APO. But in the C11

and the 20" F/4 DOB the best one could say is that the differences were small. The C11 had always put up

good views and I considered it a good scope (I sold it off about 8 years ago to a friend who still owns it.)

 

I took this to mean that if you have really good EP optics, you need to feed them with really good Objective

optics or you will end up seeing the worst (sum of) of the contributors.

[Astrojensen]

It is certainly important to notice both the type, size and the f/ratio of the scope used for testing, as the results with the same eyepiece can vary wildly between them. What works admirably in a 7" f/15 maksutov-cassegrain could be a disaster in a 8" f/4 dob. 

 

 

Clear skies!
Thomas, Denmark

[TOMDEY]

Yes, agreeing entirely with your conjecture and Mitch's and Astrojensen's responses. An eyepiece is fairly evaluated (and compared with others) using a high-quality feed (atmosphere and telescope) at the F# it is designed to accept. It's also important that your personal pupil is big enough to accept the exit pupil so-generated!

 

Of course --- for your own dedicated use... also compare with the scope(s) that you intend to use. e.g. if that's a high-end APO refractor, SCT, Big Dob with Corrector, under good seeing conditions... whatever... in which case --- what you see is what you get. So that's the entire image-chain of target type > darkness > scatter > seeing > your scope > eyepiece > your dark-adaptation > your pupil > your acuity > your perception... all of those (cept the target) being imperfect. The eyepiece itself is only one of those, and not to be confused or condemned without such qualification.

 

My biggest complaint is when evaluators condemn eyepieces, without even mentioning how they are feeding or using!  I get the feeling that more than half of condemnations are things other than the eyepiece itself.  Tom

Edited by TOMDEY, 23 September 2019 - 11:27 AM.

[CrazyPanda]

I almost feel like the reviewer's atmospheric conditions matter more than the scope. I personally don't care much for eyepiece edge correction. I'm perfectly happy with my 100 degree eyepieces in a non-coma corrected F/4.5 dob if that's any indication. My focus is always in the center, and the rest of the field is just context.

 

I only care about the following:

 

1. Contrast

2. On-axis sharpness

3. Ergonomics

 

For #1, the most accurate assessment will be done via a high quality Apo, else it's too hard to really differentiate scatter and contrast loss caused by the CO from that caused by the eyepiece.

 

#1 and #2 both depend on the atmosphere as well. I don't care what scope you have, if you have skies as crummy as mine, it will be hard to get an accurate assessment of an eyepiece's sharpness. Contrast of DSOs will depend a lot on how dark and transparent your skies are.

 

Ergonomics is really not dependent on scope type. Either an eyepiece is comfortable and has good affordance for eye placement, or it doesn't. A scope can't change that.

[rkelley8493]

I almost posted a topic about how the views are different in each type of scope, but I decided not to as I couldn't find accurate words to describe how they're different. I've always been a numbers person, they can't tell a lie , and words confuse me sometimes. I tend to get what I call "first look dyslexia" where I misread or misinterpret something if I just glance at it. 

Anyways, back to the question. I'd have to say my Apo refractor [130mm f/7]is a good judge of eyepiece performance. However, it does introduce some field curvature. FC is most noticeable in low power, wide field eyepieces when slewing the scope. It's less noticeable when the scope is at rest or slowly tracking. Certain eyepieces are better corrected for field curvature, but it doesn't get rid of it completely.

On the flip side, the Apo is a good judge of color, contrast, and optical properties of any given eyepiece. Example, the 31T5 Nagler vs ES 30/82°. The difference in color & contrast is much more noticeable in my refractor [compared to 254mm f/10 SCT] when viewing large star fields such as the Sagittarius Star Cloud. They have what I call the "fireworks" effect with different color stars at different levels of brightness. There were subtle differences that were visible comparing the two eyepieces [such as sky background, contrast, color tone, visible stars], but these differences were not as visible in my SCT.

In my SCT [10" f/10], the views have an overall different look to them. I'd compare it to a large projector at a movie theater, and the eyepiece would determine how much of the "screen" you could see. Yes, it's in high def, BUT.. the image isn't as sharp compared to my Apo [which we can call a 60" HDTV in this comparison]. More detail can be seen in the SCT, but there is a lower level contrast due to the central obstruction. Example, Jupiter's Equatorial Zone. So there are the two equatorial bands with the equatorial zone in the middle. Structure within the zone is much more visible, such as the swirling clouds, gray tendrils, and filaments, but the color is not as saturated. 

Eyepieces in the SCT all have a similar look to them. I don't really know how to explain it.. maybe like ground meat & tacos. The difference in using ground turkey and ground beef is hard to notice because of the seasoning. It's more noticeable with the fat content of the meat, 85/15 vs 73/27, but the type of meat isn't as distinguishable because of the potent seasoning and similar texture.

Edited by rkelley8493, 23 September 2019 - 11:49 AM.

[BillP]

Any field test, whether of an eyepiece or of a telescope, is actually a "system" test of the complete optical path.  When one tries to extend the results to their own circumstance, and that circumstance changes any of the variables of the field test, then results can range from the same to completely different.  And these variables include things in the optical path like elevation, transparency, seeing, experience of the observer, targets selected for testing.  The latter one, targets, is IMO a big one as over the years some targets I have found are just not good to generalize how things might appear for anything other than that single target.  So Saturn is a good example.  It is quite distant so resolvable features beyond the major ones need to be huge on the planet.  Storms in the atmospheric bands do happen but IME are not often resolvable unless you have around 10" of aperture.  So with a 4" scope as example, they would be IMO a rarity to catch.  So Saturn is more of a high contrast featured target and of course good for seeing how the warmer color pallet comes across in the "system" being tested.

 

So upshot is that one really needs to weigh and balance lots of things stated in the review to determine if and then how much the test results may be extensible to the reader's optical chain at their observing site.  Nothing is unimportant in the facts provided by the tester.  Typically this means for me that I need to pick and choose the subset of a field report I think will be relevant for me and the rest read as not pertinent for me.  All field tests I find valuable, but some for 5% of their results, others for 50% and more of their results.  And when critical things are left out, like the observing location and conditions or if optics were clean or dark adaptation or stray light at the site or protocols used for the testing, etc., then just means I have to make some assumptions which then means I have to rate the confidence level overall of the results lower.

[alnitak22]

I have seen reactions, some valid, others less so, on posts and/with reviews of eyepieces based on the telescopes used in testing them, focal length & ratio, aperture, type etc. 

 

So which scopes types & properties most validate eyepiece tests for you? Do you dismiss certain scopes types, look for all-rounders (eps & scopes), or are you only looking for what you use and want to own?

The telescopes I own and use are the only ones that matter to me. Likewise with eyepiece evaluations. The ones I make in my scopes and sky are the ones that matter. Seems pretty straightforward.

[dan_h]

Sometimes the equipment used is not as important as the who does the review. Personal biases do exist and are often visible in the results presented.   There are individuals who simply don't like anything with green lettering or have other personal preferences.. 

 

dan

[BravoFoxtrot]

It is certainly important to notice both the type, size and the f/ratio of the scope used for testing, as the results with the same eyepiece can vary wildly between them. What works admirably in a 7" f/15 maksutov-cassegrain could be a disaster in a 8" f/4 dob. 

 

 

Clear skies!
Thomas, Denmark

Well said!  This sums it up for me.  Fast scopes are the ultimate equalizer for EP’s in my experience.  

[CeleNoptic]

So which scopes types & properties most validate eyepiece tests for you?

Should be a good quality ED or APO refractor at least, reasonably fast (f/6-7 would be great) or larger reflector (e.g. 12"+) with custom high Strehl mirrors. Observing conditions (e.g. seeing) should be above average. The observer should be experienced and all the important details of the tests (equipment, conditions) should be meticulously logged and posted. I clearly see small differences between similar type EPs in my new (for me) SV102 as compared to my mass produced 8" Dob where they usually look pretty much similar.
 

Do you dismiss certain scopes types, look for all-rounders (eps & scopes), or are you only looking for what you use and want to own?

Yes, I do dismiss slow scope types which are not appropriate instruments for critical tests, IMO. I know that in my f/13 refractor all Erfles or Koenigs will perform like Naglers  .  But I carefully read/research all the tests published, bookmark and save most important of them for future references and more detailed analyses. Of course with the emphasis on what I use and may want to use in future. 

Edited by CeleNoptic, 23 September 2019 - 02:34 PM.

[Starman1]

I have seen reactions, some valid, others less so, on posts and/with reviews of eyepieces based on the telescopes used in testing them, focal length & ratio, aperture, type etc. 

 

So which scopes types & properties most validate eyepiece tests for you? Do you dismiss certain scopes types, look for all-rounders (eps & scopes), or are you only looking for what you use and want to own?

Other than a few eyepiece tests where we got to see the wavefront error figures at f/3.5 and f/7 (I'll post the links in a moment),

what matters to me is how the eyepieces perform at f/4-f/5 in a coma-corrected newtonian.

If they perform well there, they likely will perform well in SCTs, MCTs, and refractors.

Test reports:

https://web.archive....t_oculaires.pdf
https://web.archive....laires_10mm.pdf
 

Hopefully, those will work.  Translate using an add-on to your web browser if you don't read French.

 

No, I don't just look for what I want to own.  I also test for information to share with CN people and so I am informed for the public.

If this were 1995, I could say I'd owned and used nearly every eyepiece available, but that is no longer true, so I try to test them.

This weekend, for example, I'm testing 3 new eyepieces in 4.5mm, 6.5mm, 8.5mm to see how they are.

Here is my test questionnaire:

Attached Files

•  Evaluating eyepieces.docx   13.54KB   21 downloads

Edited by Starman1, 23 September 2019 - 05:05 PM.

[25585]

Thanks Don. Good questionnaire.

 

As you have CA & SAEP, what is CAEP please? 

[Starman1]

Chromatic aberration of the exit pupil.

Example: yellow or orange ring around outer edge of field when used in the daylight (aka, "Ring of Fire")

and/or different eye reliefs for different colors (example: yellow in Pentax XW eyepieces).

Usually, CAEP is a daylight problem, not a nighttime one.

[213Cobra]

I have scopes from f/3.3 to f/15. most are flat field corrected; two are triplets exhibiting FC, which I correct with aftermarket flatteners. Every eyepiece looks from quite-credible to outstanding in the F/15 Tak FOA-60Q, with same being true in the f/10 FS-60Q. So I don't pay much attention to eyepieces commentary based on views through longer FL telescopes and certainly not long FL quads. The light cones intrinsic to my f/3.3, f/5, f/5.3 Takahashi astrographs (which I use visually) challenge some eyepieces but their correction is mitigating, so those telescopes aren't my first-choice context when trying to interpret whether someone else's eyepieces commentary is actionable.

 

So, my two LOMOs are my first reference for eyepiece evaluations, especially the f/6 80/480 over the f/7.5 80/600. I routinely use a TSFlat2 with both but use the f/6 LOMO sans flattener for initial impressions of new eyepieces, then move on to the faster, corrected astrographs having established that context. The f/7.5 LOMO starts to make everything look good. I ignore any eyepiece commentary based on views through fast DOBs or other Newtonians used sans coma correction

 

Phil

[213Cobra]

I have scopes from f/3.3 to f/15. most are flat field corrected; two are triplets exhibiting FC, which I correct with aftermarket flatteners. Every eyepiece looks from quite-credible to outstanding in the F/15 Tak FOA-60Q, with same being true in the f/10 FS-60Q. So I don't pay much attention to eyepieces commentary based on views through longer FL telescopes and certainly not long FL quads. The light cones intrinsic to my f/3.3, f/5, f/5.3 Takahashi astrographs (which I use visually) challenge some eyepieces but their correction is mitigating, so those telescopes aren't my first-choice context when trying to interpret whether someone else's eyepieces commentary is actionable.

 

So, my two LOMOs are my first reference for eyepiece evaluations, especially the f/6 80/480 over the f/7.5 80/600. I routinely use a TSFlat2 with both but use the f/6 LOMO sans flattener for initial impressions of new eyepieces, then move on to the faster, corrected astrographs having established that context. The f/7.5 LOMO starts to make everything look good. I ignore any eyepiece commentary based on views through fast DOBs or other Newtonians used sans coma correction

 

Phil

[gnowellsct]

What I can tell you is that the wavefront matters.

 

At one point in time I had a 6" AP APO, a 11" SCT, and a 20" DOB, and a set of ZAO (1) orthos. So, I decided

to spend a night using these optics with those optics and see what I could <ahem> see. The chosen night was

perfect for a 6" aperture, pretty good for a 11" aperture and fairly ho-hum for a 20" aperture, so bear this in mind.

I also had (i.e., borrowed) a set of University Orthos from a friend, and had my own set of Naglers (T1 and T2);

also bear in mind this was done in the early 1990s.

 

Speaking as the owner of multiple scopes and ZAO IIs, I'm not sure how one can test the *eyepieces* in all these configurations.  I have a 92 mm f/6.9 CFF apo on top of my C14.  Its optics are excellent.  The C14 is "a good C14."  

 

But the ZAO IIs are only usable in the 10 mm and 16 mm in the C14, yielding 396x and 244x in the big guy.  And only 64 and 40x in the triplet.  396x in the triplet is over 4x per mm magnification of aperture and in no way comparable to the C14 which is at 1x per mm of aperture (optically a much less demanding spot).  244x is  still 2.6x per mm and still more a test of the scopes at hugely different exit pupils than any conceivable test of the eyepieces.

 

I have taken a bunch of 16 to 18 mm eyepieces and evaluated them across *one* scope.  But frankly I'm not sure how one can pull off a meaningful test across vastly different exit pupils in different apertures.  Even staying within brand, testing say a Pentax XW 3.5 (181x in the 92 mm refractor) against an XW 20 (196x in the C14) one is *still* not testing the eyepieces as such.  For example, it is well known that the field curvature correction in the XW20 is vastly different from the 10XW and below.  They're terrific eyepieces but not scaled designs.

 

Anyhow I test my systems every time I go out with multiple eyepiece glass and multiple optical rigs (sometimes a 92 mm refractor on top of a 130 mm) and I can say I like my oculars, which I have built up to slowly over the years, but I'm not sure I could say that even wave front variation is determining when apertures are so different as well as focal ratios and the different oculars etc.  

 

But you sure can say this or that is a performing system given the night's conditions.  Greg N

[MitchAlsup]

Speaking as the owner of multiple scopes and ZAO IIs, I'm not sure how one can test the *eyepieces* in all these configurations.  I have a 92 mm f/6.9 CFF apo on top of my C14.  Its optics are excellent.  The C14 is "a good C14."  

 

But the ZAO IIs are only usable in the 10 mm and 16 mm in the C14, yielding 396x and 244x in the big guy.  And only 64 and 40x in the triplet.  396x in the triplet is over 4x per mm magnification of aperture and in no way comparable to the C14 which is at 1x per mm of aperture (optically a much less demanding spot).  244x is  still 2.6x per mm and still more a test of the scopes at hugely different exit pupils than any conceivable test of the eyepieces.

In my testing case, the ZAOs were up against UO and both sets were Orthoscopic EPs in the same telescope; later on similar FLs of the Naglers were also compared in the same scope.

 

The surprise (to me) was that the ZAOs were clearly better in the AP APO but not "better" in the C11 (compared to the UOs). 

[gnowellsct]

In my testing case, the ZAOs were up against UO and both sets were Orthoscopic EPs in the same telescope; later on similar FLs of the Naglers were also compared in the same scope.

 

The surprise (to me) was that the ZAOs were clearly better in the AP APO but not "better" in the C11 (compared to the UOs). 

Given the FL of the ZAOs I'd guess you were past the "blur frontier" with both sets.  But actually I'm not familiar with the FLs of the ZAO I sets so I'm just guessing.  If you were testing comparable fl eyepieces (UO vs ZAO) in different apertures yes that's a good methodology, though of course the different *magnifications* of both sets in first the one and then the other apertures would make for a range of different outcomes based on the seeing, which seems consistent with what you reported, the larger apertures having more difficulty.  

 

It's really a frustrating business doing eyeball comparisons.   I think the main way oculars "sell themselves" is when an observer says "wow this is great" and then gets to test the ocular in his/her own scope.  Years ago I was at a star party where a bunch of newbie scope owners (local program gave them the scopes) got to try my 10XW instead of their comes-with plossls and that thing got passed around so much I had a hard time getting it back.  Everyone wanted it.  But of course it costs nearly as much as an Orion 8 inch, so for those on limited incomes it was out of reach.  The point being that even though they were newbies they recognized a good thing when they saw it, none of the meticulous comparos we're likely to do when we get down and dirty with the oculars.  

 

So other than these "wow" moments that observers have with different oculars there are lab tests and then pretty much everything else comes down to assembling a kit that works for the observer's personal reactions to the ocular and of course the budget.  I spent an hour once comparing an XL7 and an XW7 on a star field and nearly drove myself mad.

 

Greg N

[punk35]

I’m one of those newbs, but CN is my star party, and all of you are the advocates for whatever ep you may like/prefer in your own equipment.When I hear many positive reports of a particular ep I have some confidence it/they will be good and I might be prone to try one. 

Alas, since everyone is different, your amazing ep may be ho-hum to someone else. I really wanted to love the 13T1 N I tried, and while the view was nice the ergonomics just didn’t suit me. I didn’t say Wow! On the other hand, when I looked through a Pentax 10.5XL I did say Wow!!  I tried a Morpheus 12.5 and due to user error I didn’t have a Wow experience. I traded it for an XL7, and I have no regrets. I will probably try another Morpheus in the future. 

 

Regardless of the scope I have, everyone’s reports, regardless of the scope they are using is valid information for me and I can try to decide from those what might suit/work well for me and my equipment. 

 

I think as others have pointed out, when testing an EP your testing the system as a whole. Even though someone has the same scope and EP I do, their local conditions and personal preferences might make them say that ep sucks, while I love it. 

To each their own, and we’re both right. 

[gnowellsct]

I’m one of those newbs, but CN is my star party, and all of you are the advocates for whatever ep you may like/prefer in your own equipment.When I hear many positive reports of a particular ep I have some confidence it/they will be good and I might be prone to try one. 

That's true but I went down some expensive alleyways as a result of internet enthusiasm.  I bought a Meade 14 UWA (made in Japan) on the basis of net enthusiasm.  Might even have been before CN run by astronomics.  I bought the Nagler 17 T 4 on the basis of net enthusiasm.  

 

That's about $600 right there, maybe more.  Tried my first Pentaxes and couldn't get rid of them fast enough.  

 

Well that's OK, at least I found out that I was getting better results by shopping in the high end (after several years in low and mid levels) but didn't get to my personal KOWABUNGA till I hit Pentax.  And that was a while ago, I had time to develop an extensive line of XLs before the XWs came out.    

 

One of the obstacles I had to overcome was the large number of people willing to tell me that because I had a long FR C14 I had nothing to gain by looking into high end glass.  I'm glad I finally decided to ignore that view.

 

Greg N

[Jeff Morgan]

So which scopes types & properties most validate eyepiece tests for you? Do you dismiss certain scopes types, look for all-rounders (eps & scopes), or are you only looking for what you use and want to own?

 

Well that is certainly a two part question!

 

1) In general, I like to eliminate as many "qualifiers" and "excuses" as possible. This means using a smaller aperture refractor, one that is proven to be able to work above 50x per inch of aperture. Reasons:

 

a) Refractors have the fewest "faults", optical and mechanical. Fewer excuses and qualifiers;

b) An objective that can work above 50x per inch is going to be one of exceptional figure; and

c) Refractors tend to be smaller apertures, atmospheric seeing tends to be minimized as excuse or qualifier.

 

2) Excluding certain scopes? Need to be careful on that one. Suppose you own (and love) a f/10 Schmidt Cassegrain. No other scope is on your horizon. Do you really care how an eyepiece performs in anything else? In that case, performance in other scopes seems irrelevant.

[Jon Isaacs]

Well that is certainly a two part question!

 

1) In general, I like to eliminate as many "qualifiers" and "excuses" as possible. This means using a smaller aperture refractor, one that is proven to be able to work above 50x per inch of aperture. Reasons:

 

a) Refractors have the fewest "faults", optical and mechanical. Fewer excuses and qualifiers;

b) An objective that can work above 50x per inch is going to be one of exceptional figure; and

c) Refractors tend to be smaller apertures, atmospheric seeing tends to be minimized as excuse or qualifier.

 

2) Excluding certain scopes? Need to be careful on that one. Suppose you own (and love) a f/10 Schmidt Cassegrain. No other scope is on your horizon. Do you really care how an eyepiece performs in anything else? In that case, performance in other scopes seems irrelevant.

 

Small refractors generally have significant field curvature. 

 

My own thinking:  

 

The scope should be free from it's own aberrations, field curvature, coma, chromatic aberration. Fast scopes are best for testing off axis aberrations.

 

I "test" eyepieces in my scopes. They're generally fast and corrected for coma and field curvature.. 

 

Important to me are sharpness both on and off-axis, scatter and contrast, freedom from EoFB, enough eye relief that I can take in the entire view.

 

I read most reviews with a certain skeptism and look for signs of the observers experience. 

 

When I want to know about a particular eyepiece, I send Don a PM.

 

Jon 

[25585]

I’m one of those newbs, but CN is my star party, and all of you are the advocates for whatever ep you may like/prefer in your own equipment.When I hear many positive reports of a particular ep I have some confidence it/they will be good and I might be prone to try one. 

Alas, since everyone is different, your amazing ep may be ho-hum to someone else. I really wanted to love the 13T1 N I tried, and while the view was nice the ergonomics just didn’t suit me. I didn’t say Wow! On the other hand, when I looked through a Pentax 10.5XL I did say Wow!!  I tried a Morpheus 12.5 and due to user error I didn’t have a Wow experience. I traded it for an XL7, and I have no regrets. I will probably try another Morpheus in the future. 

 

Regardless of the scope I have, everyone’s reports, regardless of the scope they are using is valid information for me and I can try to decide from those what might suit/work well for me and my equipment. 

 

I think as others have pointed out, when testing an EP your testing the system as a whole. Even though someone has the same scope and EP I do, their local conditions and personal preferences might make them say that ep sucks, while I love it. 

To each their own, and we’re both right. 

I bought a 13T1 new long ago. When it worked my wow was on DSOs. But its design & optical issues made it more antagonising than gratifying. Now the wow is back with an ES92 12mm 30 years later.

 

Between those 2 eyepieces, I have bought and tried many. Initially my scopes were all F5, refractor and reflector. Aperture can up the wow factor faster than any eyepiece. At first anyway. But though not jaded, any eyepiece that keeps my buzz going, time after time, whatever make or design it may be, is a keeper. 

[rkelley8493]

I came across an issue that I hadn't noticed before when using the ES 14/100°. A few months back, I was comparing the 13 Ethos with the 14/100, and I found the performance almost identical. I believe my targets where Bernice's Coma and Ursa Major [the galaxies in that region]. 

Well the other night, I was sweeping the Sagittarius Star Cloud and the surrounding nebulae, and I noticed some cursed edge of field brightening. Granted it wasn't very bright, it was still noticeable because it kept tricking me into thinking I was seeing clouds of gas & dust that weren't really there. But then again, this portion of the sky is right in the path of my neighborhood street lights, so the fault could lie with light scatter. 

Anyways, my point is that there are some other factors that come into play when judging performance of an eyepiece, light pollution & scatter are a couple factors. Some eyepieces do a better job at cutting down the light scatter. I can usually tell by examining the eyepiece during the daytime or inside my house with the lights on. I just hold the eyepiece with the field lens in the direction of a light source or window and examine the exit pupil. If it is an image surrounded by blackness, then it is an eyepiece with minimal scatter. If it is an image surrounded by gray or another reflective circle, then it is poor at managing light scatter. In other words, you can see if there is light scattering within the eyepiece even when it's not being used in a scope.