32 replies to this topic

[dhferguson]

Cheers,

 

Certainly premium eyepieces from Televue and others perform better than less expensive options for light cones of f/5 and below. However, f/10 is far more forgiving. So I do have two questions:

 

--I prefer the larger available FOVs of 2" eyepieces in low powers and dislike using adapters. So, for two-inch eyepieces, which perform very, very well across the focal length range of 3.5mm to 30mm at f/10? I prefer AFOVs of 68 deg or greater at lower magnifications (say, focal lengths => 12mm). No need to stick to one manufacturer, BTW and

 

--for 1.25" eyepieces, same question.

 

By perform, I mean sharpness and lack of aberrations to the edge-of-field, and perhaps transmission. Also, eye relief s/b at least 12mm and, even better, 15mm or above.

 

I realize there are other factors: cost and weight among them. Let's ignore these for now. BTW, I observe with a C8 Edge. Eyepieces do not correct for field curvature anyway, so no need to comment on this.

 

Happy observing always,

 

Don

 

[MrRoberts]

With my C-8e at f10 I use either the 31 nagler, 17 and 10 ethos or in 1.25, the 24 pan, 16 and 9 naglers. 

This ota is killer with my MOD3 NV afocal 40 ploss also

 

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[SeattleScott]

Pentax XW comes to mind, but pricey, not taking advantage of your slow F ratio.

Baader Hyperions would be cheaper, 68-70 AFOV, good eye relief, 3.5 to 31 focal lengths. They have 2” barrels so no adapter required. Some bench test less than perfect at F10, but they won’t be “bad” at F10, so it just depends on how picky you are about edge correction. Certainly, the AFOV and ER are there, no adapter required, and the price is right. They have the focal lengths you want. Just not all focal lengths will be quite sharp to the edge.

AT UWA is even wider, but less ER (12-15mm), still within your range though. Focal lengths of 4 to 28, some odd spacing however, like 4, 8, 10. Also a gap of 16 to 28, but there is a 21 coming out. The 16 is the weak link. It should still be a pretty good performer at F10, but perfection might be an unrealistic goal.

In general, affordable eyepieces are inconsistent. So while you can get by with them at F10, some focal lengths will be better than others, and it might be unrealistic to expect all of them from the same series to be sharp to the edge even at F10. Some focal lengths will be, but some might not. And everyone is different regarding what they consider sharp to the edge.

Also, less expensive eyepieces typically don’t have the same level of light suppression and polish, so contrast is usually a touch worse than premium brands. Might be hard to see the difference with a complex optical system like a C8 Edge though. But the bottom line is cheap eyepieces don’t perform quite as well as premium brands even at F10. Granted for the difference in price, one might find them quite acceptable.

Edited by SeattleScott, 16 March 2025 - 01:01 PM.

[dmgriff]

The moderately priced Speers Waler 31.5mm 90 degree afov 2in eyepiece has been commented as good in slow otas, not in fast ones. 

https://www.cloudyni...ers-waler-hmer/

 

re posts #62. 107-112. for some of the OP perspectives/photos

post #138 final review. Keeper for OP (slow ota)

 

Available thru ScopeStuff (remark it is a "killer eyepiece")  ~140usd

https://www.scopestuff.com/ss_sw2x.htm

Edited by dmgriff, 16 March 2025 - 01:17 PM.

[dhferguson]

Cheers,

 

I agree, I've been using sundry Televue eyepieces for years with a number of telescope types, including Dobs. Now that I've "downsized" to an 8" SCT, I'm wondering if the Naglers and Ethos eyepieces aren't overkill.

 

Good point regarding polish. I've barely ... and I mean barely ... seen Sirius B using the C8 Edge and an Ethos 6mm under good-to-very good seeing, latitude 37.6 deg N. There is a bit of small-angle scatter, which I assume is due to the polish smoothness of the OTA.  A 10" Newt with premium mirrors showed considerably less scatter, and Sirius B was easier.

 

How sharp at the edge of FOVs are the Baader and AT UWA offerings at f/10? Sharp to me is pinpoint, like Ethos.

 

Interesting but somewhat expected that less expensive eyepiece lines would be inconsistent. This is true but to a lesser extent even with the premium brands. Which are the "good" Hyperions, AT UWAs?

 

Happy observing always,

 

Don

[SeattleScott]

See this link, F10 columns, smaller numbers are better, 10 or less should look basically perfect. Look for the AT UWAs under William Optics UWAN label.

http://astro-talks.r...opic.php?t=1483

[Procyon]

Best Eyepieces for f/10 Optics?

 

 

Invest in a good eyepiece that gives you a 2mm exit pupil. Something like a 20mm APM 100/21mm Ethos if those don't give you the kidney bean effect. Try a twist top 20mm 100 if they do. Or go all out and get a 17/14mm Nikon HW. One of these will be your main eyepiece for Open Clusters and heavy backyard usage. You'll see a huge patch of dark sky with it, guaranteed to impress. Add a 9-10mm Delos/Pentax XW/Morpheus for planetary work. I'd start with those 2 than get something like a 35mm Panoptic for Nebulae at a dark site. Just my opinion, there's other roads you can take, just plan it out to your liking.

 

PS> 28mm AT UWA, 13mm AT XWA seem attractive too.

 

The moderately priced Speers Waler 31.5mm 90 degree afov 2in eyepiece has been commented as good in slow otas, not in fast ones. 

https://www.cloudyni...ers-waler-hmer/

 

re posts #62. 107-112. for some of the OP perspectives/photos

post #138 final review. Keeper for OP (slow ota)

 

Available thru ScopeStuff (remark it is a "killer eyepiece")  ~140usd

https://www.scopestuff.com/ss_sw2x.htm

I have this eyepiece sitting around since 2021 and never got a chance to use it. I'm surprised Scopestuff still calls it a killer eyepiece. Seems they actually meant it lol. Need to try it very soon/

Edited by Procyon, 16 March 2025 - 04:11 PM.

[PKDfan]

Invest in a good eyepiece that gives you a 2mm exit pupil. Something like a 20mm APM 100/21mm Ethos if those don't give you the kidney bean effect. Try a twist top 20mm 100 if they do. Or go all out and get a 17/14mm Nikon HW. One of these will be your main eyepiece for Open Clusters and heavy backyard usage. You'll see a huge patch of dark sky with it, guaranteed to impress. Add a 9-10mm Delos/Pentax XW/Morpheus for planetary work. I'd start with those 2 than get something like a 35mm Panoptic for Nebulae at a dark site. Just my opinion, there's other roads you can take, just plan it out to your liking.

I have this eyepiece sitting around since 2021 and never got a chance to use it. I'm surprised Scopestuff still calls it a killer eyepiece. Seems they actually meant it lol. Need to try it very soon/

I have it Procyon and at F/10 it'll be decent but it really likes a slow ratio to perform.

In its favour its super immersive, super easy pupil and great transmission in addition to being ultra light.

Tax it at even F/8 and it'll probably disappoint some. With my F/9 i'm using it as a dedicated line filter eyepiece.


Its a Maksutov speed eyepiece ideally.

And a good Barlow eyepiece i imagine.


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Lance

[PKDfan]

Will it claim dhferguson as a new victim?

Its a bargain asset.


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[Jay_Reynolds_Freeman]

Cheers,

 

Certainly premium eyepieces from Televue and others perform better than less expensive options for light cones of f/5 and below. However, f/10 is far more forgiving. So I do have two questions:

 

--I prefer the larger available FOVs of 2" eyepieces in low powers and dislike using adapters. So, for two-inch eyepieces, which perform very, very well across the focal length range of 3.5mm to 30mm at f/10? I prefer AFOVs of 68 deg or greater at lower magnifications (say, focal lengths => 12mm). No need to stick to one manufacturer, BTW and

 

--for 1.25" eyepieces, same question.

 

By perform, I mean sharpness and lack of aberrations to the edge-of-field, and perhaps transmission. Also, eye relief s/b at least 12mm and, even better, 15mm or above.

 

I realize there are other factors: cost and weight among them. Let's ignore these for now. BTW, I observe with a C8 Edge. Eyepieces do not correct for field curvature anyway, so no need to comment on this.

 

Happy observing always,

 

Don

Credentials: I have done a lot of observing with instruments in the range f/9 to f/11 -- C-14, C-8, Intes 6-inch f/10 Maksutov, several refractors with apertures of 80 to 127 mm.

 

There is a tradeoff in using very wide-field eyepieces which causes me to avoid them where possible: Every air/glass interface in the eyepiece is an opportunity for more light loss by reflection from coated surfaces, and for more light scattered or reflected into the sky background, via surface irregularities in the coatings in the first case and multiple reflections in the second -- and some wide-field eyepieces have ten or more air/glass interfaces. Furthermore, the total thickness of the lenses in some such eyepieces is enough to cause noticeable light loss due to absorption in the glass itself -- I am thinking of eyepieces that use certain lanthanum glass types.

 

That said, for these instruments I usually use a 40 mm Erfle or Vernonscope wide-field eyepiece for low magnifications and as an aid for finding things -- that gives a 4 mm exit pupil and a 65 to 70 degree apparent field, and the field lens nearly fills a two-inch eyepiece barrel anyway. These eyepieces have four or six air/glass interfaces. For more magnification, I generally grab one or another classic Brandon -- 32, 24, 16, 12 or 8 mm, four air/glass interfaces, about a 45 degree apparent field. When I want even higher magnification I reach for a Takahashi orthoscopic (four air/glass interfaces, about a 45 degree apparent field) or perhaps a Tele Vue 3-6 mm zoom Nagler (six air/glass interfaces, 50 degree apparent field).

 

At f/10, all of these eyepieces provide excellent images at the center of the field and pretty good images elsewhere, with high transmission and little scattered light. Except for the zoom Nagler, the shorter focal length units have eye relief that you, or anyone who must wear glasses while observing, would probably find too short.

 

Thus my answer to your question is that in my opinion, super wide-field eyepieces in general are unsuitable for use at f/10, because of the tradeoffs discussed. There may be exceptions for eyepieces that I am not familiar with. I suspect my opinion is uncommon on CloudyNights.

 

I am not telling you or anybody else not to use such eyepieces, but I do suggest that you carefully consider the tradeoffs encountered in doing so, and test any prospective eyepiece carefully before committing to a purchase.

 

 

Clear sky ...

[Mike Q]

In my F10 10 inch SCT i run my Orion Q70s.  I have no issues with them in that scope.  If i need or want more i have my Orion 14 and 20mm LHDs that work quite well in it.  I have yet to run into a need to go much stronger then the 14mm as of yet 

[dhferguson]

Cheers,

 

Thank you, JRF, for your thoughts on minimizing scatter by minimizing air-glass interfaces within eyepieces. But such a tradeoff would mean giving up a wide AFOV for something like 50 deg or less, a trade I am not willing to make, except perhaps at the highest power for planets.

 

Thank you too, "Seattle Scott", for the link to the "Ernest's" (the Russian). evaluation of eyepieces. I believe he has done a diligent job in evaluating a large but still incomplete variety of eyepieces. With criteria of 68 deg AFOV or larger and, at f/10; center, half-field, and edge-of-field spot size no greater than 5 arcmin, I identified over twenty eyepieces. Some of these are no longer made and others are rather rare.

 

However, one obvious trend stands out: it appears in general that the spot sizes generally increase with larger eyepiece focal lengths. There are many choices at or below, say 12mm but few at larger wavelengths. Now an edge-of-field spot size of 5 arcmin is a stringent requirement, and perhaps that might be relaxed for longer wavelengths?

 

Another thing that stands out: a very few eyepiece lines pretty much meet (or at least come very close) to meeting my spot size criterion at focal lengths at or below 12mm, and then there are just a few good outliers thrown in. Among the eyepieces  that meet my criteria are:

--Televue: Delos, Ethos, and the T6 lines; also the Nagler 9mm T1,

--Baader: Morpheus 4.5mm, 6.5mm,

--Meade: PWA 5000 4mm & 7mm and UWA5000 5mm & 8.8mm, and

--Nikon NAV 7mm.

 

The only William Optics in the bunch was the UWAN 4mm, same as the AT XWA clone, I believe.

 

Among the eyepieces of longer focal length than 12mm, only the following met the criteria:

--Celestron Axiom 19mm and

--Televue Nagler T5 31mm.

 

Ernest also listed specific aberrations in most cases. In general but not always, smaller spot size was correlated with less aberration. 

 

Specifically, two eyepieces did not meet my two criteria, although they scored quite well. These include the ES 82 deg AFOV 30mm, which I own, and the much-boosted ES 92 deg AFOV 17mm. Nor did any of the Pentax XW line make the cut, although several were close.

 

I had hoped that narrowing the telescope light cone from a Dob-like f/5 to a more forgiving f/10 would reveal a good number of eyepieces that performed to near-perfection, even some of the less-expensive ones. This latter was clearly not the case. Guess I'll stick with what I have: Ethos 4.7mm, 6mm, and 10mm; Nagler T2 20mm (not tested but very sharp indeed), and ES 82 deg AFOV 30mm. I do sometimes use others' telescopes, and they will do well there too, of course. Oh well.

 

Happy observing always,

 

Don

[SeattleScott]

Ok let's be realistic. I have a 15 Panoptic. I have a F4 scope with coma corrector. Ernest says the spot size at the edge at F4 is 13.

I have tested it and specifically looked for edge abberations. If I try hard enough, I can tease them out. But I have to try. Basically, it takes putting a fairly bright star almost right at the field stop to see abnormalities in star shape. So if I try hard enough, I can detect edge abberations with a spot size of 13. But in normal viewing, I would almost never (maybe never) notice. And that's with a spot size of 13, not 5.

Remember, that Nikon 7 SW you looked at, it has a spot size at the edge at F4 of 12. Ernest gave it an excellent rating. It will give sharp views to the edge at F4. At F10, it is overkill.

By setting a max spot size of 5, you are demanding more perfection than your eye can possibly discern. That's why you are finding yourself limited to Ethos and the like, even at F10. Now sure, you will get sharp stars to the edge of the field. But there are a lot of other eyepieces that would provide sharp views to the edge of the field.

the 4 UWAN is the same as the AT UWA (not XWA) and Meade PWA.

Also, the APM 30UFF has a spot size of 4 at the edge at F10. I don’t know if it would be my first choice for a SCT though.

Edited by SeattleScott, 16 March 2025 - 09:40 PM.

[dhferguson]

Cheers,

 

Yes, "Seattle Scott," for someone starting anew with an f/10 scope I would agree.

 

I deliberately set the spot angular size criterion tight--barely discernible according to Ernest--to see if I'd be giving up anything by moving to less expensive eyepieces. For the ones I own of less than 12mm focal length, that answer is yes; in particular, field of view. I value field-of-view but it is a part of every eyepiece's spec sheet (give or take a degree or two) so no need to ask here. I too have performed the bright-star-at-edge-of-field test. All mine are perfect except for the ES 30mm, which is very close, as Ernest's results would indicate.

 

So I'd mostly be trading AFOV for a few hundred dollars, something I am not going to do,

 

BTW, I forgot to mention that the Panoptic 24mm is a special eyepiece. According to Ernest, it scores very well (but not quite perfection) in spot size. It has about the largest field lens that fits within a 1.25" barrel, and so provides the widest field in that barrel size. I achieve a 1.2 deg FOV with the 30mm ES and a 2" barrel but the Panoptic would yield a 0.8 deg FOV were I to switch to the much lighter 1.25" size in toto. I'll take the larger FOV but others might choose differently.

 

Happy observing always,

 

Don

[SeattleScott]

Well, Televue's forte is very wide AFOV with excellent edge correction. So if you already have Naglers and Ethos, and your standards are absolute perfection at the edge of the field, you aren't going to be able to improve on that. It is kind of TV or nothing at that point.

 

That being said, sometimes one can't see the forest through the trees. You are very focused on edge correction in bench tests and treating it like it is the only measure of performance. Quantitative, ok, maybe. But there are other performance factors. They are just harder to measure. That doesn't mean they aren't real.

 

There is fairly broad consensus that the 17 Nikon HW is a sharper eyepiece than the 17 Ethos. Now, the 17 Ethos tests a little better at the edge of the field at F10. I doubt you could tell them apart if someone offered you a million dollars, but technically it tests better at the edge, while the Nikon tests a touch better in the middle. But people fairly consistently say they like the view through the Nikon better. Is it the polish? Is it Taiwan glass versus Japanese glass? Idk, I don't have these eyepieces. But from what I have read, the Nikon is detectably sharper (subtly I'm sure, but detectable). So you are ignoring pretty good consensus that the Nikon is detectably sharper contrast, and instead focusing on an almost certainly undetectable difference in edge correction at the extreme edge (spot size of 5 versus 7). Even Ernest thinks the Nikon surpasses the "iconic" 17 Ethos in image quality, and says it is perhaps the best hyperwide he has ever gotten his hands on. He states, "If you do not reckon with the costs and are a perfectionist at heart - this eyepiece is for you!" 

https://astro-talks....php?f=32&t=4702

 

Believe me, I wish a spreadsheet could tell us what the very best eyepieces are. Unfortunately, it isn't that simple. Tests on edge correction are a great start. But there is also baffling, blackening, polish, coatings, etc. All of these play into the view through the eyepiece. I mean, why would someone pay $1,300 euros for an 84 AFOV eyepiece when Televue offers 82-110 eyepieces with essentially perfect edge correction already, at lower cost?

 

All that said, if you already have the 17 Ethos, do you really want to pay $1,000 to perhaps get a detectable increase in contrast? Maybe not.

Edited by SeattleScott, 16 March 2025 - 11:26 PM.

[SeattleScott]

FWIW I recently read a post about someone performing some kind of test to evaluate polish, and their 20T2 clearly had superior polish compared to their Delos (I don't recall a particular Delos focal length being mentioned). Personally, I have been kind of put off by the sheer size and weight of the 20T2, and the old coatings no doubt transmit less light than newer eyepieces. But people sure do rave about the view through the 20T2. It might be an oversized dinosaur by today's standards, but I get the impression there is something special about the view. Might be the polish. Delos are arguably the very best eyepiece series out there if you go by Ernest's bench test scores. But that doesn't necessarily mean they are the very best eyepieces out there. 

[dhferguson]

Cheers,

 

"Seattle Scott", you ask, why would someone spend $1300 euros ... ? I guess the same sort who would pay up for an Apollo 11. That person is not me. Also, I don't own a 17mm Ethos. It  would yield about the same FOV as my 82 deg AFOV  Nagler T2 20mm (an oldie) but, of course, yields a bit more magnification. That and the slightly better transmission is not worth it to me either.

[SeattleScott]

Then I think you are set. You aren't going to get much better than what you already have, and it would cost a lot to get any improvement.

 

And it sounds like you don't want to downgrade. So all signs point to standing pat.

 

(You might want to go back and read what I posted about the 20T2; our posts went up about the same time, so you probably missed it).

Edited by SeattleScott, 17 March 2025 - 12:23 AM.

[dhferguson]

Cheers,

 

Yep. Thanks for helping me decide.

 

Happy observing always,

 

Don

[PKDfan]

Then I think you are set. You aren't going to get much better than what you already have, and it would cost a lot to get any improvement.

And it sounds like you don't want to downgrade. So all signs point to standing pat.

(You might want to go back and read what I posted about the 20T2; our posts went up about the same time, so you probably missed it).

Hi Scott !

Please Please as i know you are a Lover of fine astronomical gear you MUST try the magical 20T2 Nagler. I PROMISE you you'll be kicking yourself blue from not trying it before.

I have only two eyepieces that i'd ball like a little baby if harm came to them. 12T2 & 20T2.

My jaw drops everytime i use them.

20T2 is 45X 2.22mm exit pupil and about 1 3/4° true field in my 100ED. Visual gold.
Edit i should add the 12T2 Nagler is 75X and lunar views are where Keplers apron of butterscotch colour was in your face bold instead of a mere hint.


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Lance

Edited by PKDfan, 17 March 2025 - 06:11 AM.

[SeattleScott]

Hi Scott !

Please Please as i know you are a Lover of fine astronomical gear you MUST try the magical 20T2 Nagler. I PROMISE you you'll be kicking yourself blue from not trying it before.

I have only two eyepieces that i'd ball like a little baby if harm came to them. 12T2 & 20T2.

My jaw drops everytime i use them.

20T2 is 45X 2.22mm exit pupil and about 1 3/4° true field in my 100ED. Visual gold.
Edit i should add the 12T2 Nagler is 75X and lunar views are where Keplers apron of butterscotch colour was in your face bold instead of a mere hint.


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Lance

I will keep that in mind!

[PKDfan]

I will keep that in mind!

Lol i can also promise you Scott that you wont find it for less than the 345CDN i paid for it. No box and it lost most of its value i guess LOL.


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Lance

[SeattleScott]

Lol i can also promise you Scott that you wont find it for less than the 345CDN i paid for it. No box and it lost most of its value i guess LOL.


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Lance

I suspect you are right. Gives me an idea of target price.

[25585]

I have a 20T2 that I let others look thru, while I use my 20 LHD LER, horses for courses.

[PKDfan]

I suspect you are right. Gives me an idea of target price.

2019 prices, canadian dollar prices so Ages ago.


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