26 replies to this topic

[Sreesha]

I have a dobson 12.5"  f/4.5

 

If money is not a constraint please advise if it would make it worth to buy Tele Vue Ethos 21m, instead Nagler Type 4 22mm?

 

what difference does it make?  would it be worthy going for the ethos?

 

please advise

[TayM57]

Glasses, N22T4.

 

No glasses? 21E.

 

Both are excellent eyepieces but both offer difference experiences. I've had both. If I didn't have to wear glasses, I'd go with the 21E any day and twice on sundays.

[SeattleScott]

Do you use a coma corrector?

[Sreesha]

Glasses, N22T4.

 

No glasses? 21E.

 

Both are excellent eyepieces but both offer difference experiences. I've had both. If I didn't have to wear glasses, I'd go with the 21E any day and twice on sundays.

Thanks.  If my telescope has built in diopter, where I can adjust the eyepower, what would you suggest?

[Sreesha]

Do you use a coma corrector?

No.

[SeattleScott]

No.

Then the answer is easy. Neither.

The Ethos is too wide of AFOV to use at F4.5 without a coma corrector. The 22 Nagler isn’t corrected well enough for use at F4.5 without a Paracorr, and coma will be an issue for it too.

Perhaps a 30mm 70 AFOV Ultra Flat Field? Or a 27 Panoptic? Maybe a 25 Xcel LX?

Or get a P2 and unlock the power of Televue ultrawides and hyperwides.

[havasman]

My choice is 21E because I don't care for long eye relief at all. For lightweight eyepiece in the focal length range I have a 20T5 and it's very fine. Folks that need LER tend to love the 22T4.

 

You really do want a coma corrector at f4.5. You will very likely see a big difference in the outer 1/4 of the field. Any field.

Edited by havasman, 23 March 2025 - 11:57 AM.

[TayM57]

My choice is 21E because I don't care for long eye relief at all. For lightweight eyepiece in the focal length range I have a 20T5. Folks that need LER tend to love the 22T4.

 

You really do want a coma corrector at f4.5. You will very likely see a big difference in the outer 1/4 of the field.

Well, for folks who really love LER EPs, the Morpheus are the answer to that. The Delos/Delites have lots of ER.

 

In comparison, the N22T4 feels tight.

[TayM57]

Or get a P2 and unlock the power of Televue ultrawides and hyperwides.

This is what I would do.

[Sreesha]

Well, for folks who really love LER EPs, the Morpheus are the answer to that. The Delos/Delites have lots of ER.

 

In comparison, the N22T4 feels tight.

isn't then N22T4 better than E21 in terms of eye relief?  

 

those who have eyepower, isn't N22T4 better than E21?

[SeattleScott]

isn't then N22T4 better than E21 in terms of eye relief?

those who have eyepower, isn't N22T4 better than E21?

The 22 has more eye relief, and is generally considered glasses compatible, although it might be borderline for some.

The Ethos is a newer design and better corrected, but not designed for use with glasses.

The 22T4 is one of the oldest TV designs still in production. The Type 4s were followed by Type 5s and Type 6. Then Ethos. So the Ethos is a few generations newer. The Type 7s come out early summer.

In particular, the 22T4 has a bit of field curvature that benefits from a Paracorr 2. So the P2 is kind of critical for the 22T4 at F4.5, as it not only solves coma from the mirror, but also helps clean up the FC in the eyepiece.

Edited by SeattleScott, 23 March 2025 - 12:19 PM.

[TayM57]

isn't then N22T4 better than E21 in terms of eye relief?  

 

those who have eyepower, isn't N22T4 better than E21?

I wouldn't say that one is better than the other. Different tools for different jobs, is how I would look at the two.

 

Yes, the N22T4 is more comfortable however, those who don't wear glasses at the EP do tend to struggle with long eye relief, and the N22T4 has 16mm of effective eye relief, per Don.

 

The 21E will have an effective eye relief of around 11-12mm judging from Don's measurements of the 8E, 6E.

 

Not sure what you mean by eyepower. Glasses? If so, yes the N22T4 is a better fit for those who wear glasses. I cannot wear glasses with any eyepiece with an effective ER of 14mm or less. The A11 worked for me, but it was tight at 14.8mm of eye relief. The N22T4 is more comfortable.

 

I would be thinking about your own preferences first. Have you looked through an Ethos? Nagler? Delos/XW?

[havasman]

isn't then N22T4 better than E21 in terms of eye relief?  

 

those who have eyepower, isn't N22T4 better than E21?

Better is probably not the right word in either place. 22T4 is designed to have longer ER than a 21E. Better or worse depends on what the user likes.

 

It's not clear what you mean by eyepower.

 

Both the 21E and 22T4 are highly valued eyepieces that perform at the highest levels. Their differences are variables that form a basis for an observer's choice of which one may best fit their kit. Understanding that should give the user an opportunity to make a good choice and be "right" whichever one they choose.

[Keith Rivich]

Then the answer is easy. Neither.

The Ethos is too wide of AFOV to use at F4.5 without a coma corrector. The 22 Nagler isn’t corrected well enough for use at F4.5 without a Paracorr, and coma will be an issue for it too.

Perhaps a 30mm 70 AFOV Ultra Flat Field? Or a 27 Panoptic? Maybe a 25 Xcel LX?

Or get a P2 and unlock the power of Televue ultrawides and hyperwides.

While what you say is technically true both eyepieces work quite well in my 18" f4.5. Yes, the outer edges aren't crisp but that doesn't bother me unless I am looking at some DSO's where the edges matter. Then I slip in my P2. Otherwise everything I need to see is in the middle third of the eyepiece. 

[SeattleScott]

While what you say is technically true both eyepieces work quite well in my 18" f4.5. Yes, the outer edges aren't crisp but that doesn't bother me unless I am looking at some DSO's where the edges matter. Then I slip in my P2. Otherwise everything I need to see is in the middle third of the eyepiece.

The way I see it, if I’m paying $900 for a 21E or half as much for a 22T4, it better be pretty sharp to the edge, or at least have the ability to be sharp to the edge when I want it. If the outer view is going to be messy anyway, then I would get a 20XWA or a 20 Founder Optics Marvel for a third of the cost (either way).

I mean, yeah, you hear about people using hyperwides without a coma corrector at F5. But very rarely Ethos. Normally with XWAs or other Chinese hyperwides. Bruce does use Ethos without coma corrector, but that’s largely due to clearance issues with barlowing the Ethos in a coma corrector. Generally speaking, there is little point to buying the most expensive, top tier eyepieces at F4.5 if a coma corrector isn’t in play.

Edited by SeattleScott, 23 March 2025 - 02:51 PM.

[GGK]

Yes, the N22T4 is more comfortable however, those who don't wear glasses at the EP do tend to struggle with long eye relief, and the N22T4 has 16mm of effective eye relief, per Don.

This is misleading because the statement does not consider the adjustable eye cup on the 22mm NT4. 

 

I don't wear eye glasses, but when available, I prefer long eye relief with an adjustable eye cup because I can raise the eyecup to significantly shorten the effective eye relief, while keeping the eye lens further from my eye at the same time. This enables me to put my face against the rubber eye guard for easy eye placement, while keeping my eye lashes from contacting the eye lens. When I fully extend the eye cup of the 22mm NT4, I believe the effective eye relief is actually shorter than the 21mm Ethos because I can see the full Ethos field of view, but cannot see the full field in the 22NT4 until I push the eye cup down a little.  I use the 22NT4 and Delos the same way -- fully extend the eye cup, position my eye while keeping light contact between my face and the rubber eye guard, then pushing the eye cup down until I can easily see the full field.  Very comfortable and easy to use.  The Delites have a similar adjustable eye cup to Delos, but I need to adjust them differently because of the iris in the top of the eye cup that stays at the top even when the eye cup is raised.    

 

The Ethos has a fixed rubber eye guard with adequate eye relief that enables me to make contact between my face and the rubber eye guard for good eye position.

 

I'm one who finds the Morpheus very difficult to use for the reason you state - the eye relief is a bit longer than I like and although I've tried many times to hit the right eye guard height / spacing with many O-Ring combinations, plus trying a Tele Vue eye guard extender, I have not yet found an optimal setting that's easy and comfortable every time.  So, I tend to get black-outs, especially with the 9mm.  I do better with the 4.5mm.   

 

Gary

[Sreesha]

Thank you all for the inputs.  Let me explore further.

[jakecru]

I have both. The 22 Nagler T4 used to be my favorite eyepiece, it is definitely one of the more comfortable eyepieces. I prefer the view the 21 Ethos gives, I think it's slightly more contrast and definitely wider (and a lot heavier). The 22 Nagler has remained in my case and is eyeglass friendly where the 21 Ethos is not. I may eventually sell it to go towards funding a 19 mm Nagler T7. They both are great eyepieces. I find myself using the 21 Ethos more in my large Obsession dobsonian telescope. It balances well with the 31 Nagler with magnetic counterweights on the back,and I can easily remove 1 counter weight to offset switching to the lighter delos and xw eyepieces. I prefer the wider view it offers since that scope doesn't track.

[CHASLX200]

Gotta have a Paracorr for sharper edges of the FOV for fast Newts.

[Jon Isaacs]

The way I see it, if I’m paying $900 for a 21E or half as much for a 22T4, it better be pretty sharp to the edge, or at least have the ability to be sharp to the edge when I want it. If the outer view is going to be messy anyway, then I would get a 20XWA or a 20 Founder Optics Marvel for a third of the cost (either way).

I mean, yeah, you hear about people using hyperwides without a coma corrector at F5. But very rarely Ethos. Normally with XWAs or other Chinese hyperwides. Bruce does use Ethos without coma corrector, but that’s largely due to clearance issues with barlowing the Ethos in a coma corrector. Generally speaking, there is little point to buying the most expensive, top tier eyepieces at F4.5 if a coma corrector isn’t in play.

 

My friend Bruce has an 18 inch F/4.5 Obsession, He has a Paracorr but rarely uses it.  He does the vast majority of observing with the 17mm and 13mm Ethos along with a various combinations of Barlows and Extension Tubes.

 

I use a Paracorr 2 in all my Dobs views through his scope, the way he does it, are surprisingly good.

 

I had the 21mm Ethos, it's a great eyepiece but it's a heavy eyepiece.  A couple of years ago, I borrowed an Astro-Tech 20mm XWA for about 4 months to compare them.  After 4 months, I decided the 20mm XWA was plenty good enough for me and I did like the fact that it's about 2/3's the weight of the 21 mm Ethos.  I gave the Ethos to a friend to sell. 

 

My main DSO scopes are both F/4.4.  I recommend to sreesha at least considering the 20mm XWA.  

 

Jon

[SeattleScott]

Bruce is making a choice to sacrifice edge of field for his barlow/extension system that allows him to achieve optimal magnification for many targets with just two eyepieces. Now one could argue that he might have overpaid because he is using these expensive Ethos instead of XWA without coma corrector, but it isn’t like there is a 17XWA, and with what he has invested in astronomy gear, he probably wasn’t concerned about the cost difference between the 13XWA and the 13E. Presumably the 13E has some central field contrast advantages due to glare suppression, polish or what not. Most people who don’t bother using a coma corrector with hyperwides in a fast newt probably won’t want to pay up for Ethos. Especially if the $500 price tag is part of why they don’t use a coma corrector. That’s not Bruce.

I agree, the 20XWA (or Marvel) seem like great alternatives to a 21 Ethos, especially if the OP doesn’t want to use a coma corrector at F4.5. After all, you use the 20XWA over the 21 Ethos even though you have a coma corrector, because of size/weight issues.

Edited by SeattleScott, 26 March 2025 - 02:20 PM.

[TayM57]

Bruce is making a choice to sacrifice edge of field for his barlow/extension system that allows him to achieve optimal magnification for many targets with just two eyepieces. Now one could argue that he might have overpaid because he is using these expensive Ethos instead of XWA without coma corrector, but it isn’t like there is a 17XWA, and with what he has invested in astronomy gear, he probably wasn’t concerned about the cost difference between the 13XWA and the 13E. Presumably the 13E has some central field contrast advantages due to glare suppression, polish or what not. Most people who don’t bother using a coma corrector with hyperwides in a fast newt probably won’t want to pay up for Ethos. Especially if the $500 price tag is part of why they don’t use a coma corrector. That’s not Bruce.

I agree, the 20XWA (or Marvel) seem like great alternatives to a 21 Ethos, especially if the OP doesn’t want to use a coma corrector at F4.5. After all, you use the 20XWA over the 21 Ethos even though you have a coma corrector, because of size/weight issues.

I agree that Bruce is sacrifacing sharp stars at the edge for his barlow system. I've had Ethos before, so it's been a while, but it could be that stars at the edge are too far in his peripherical vision that the aberrations don't bother him, so he's decided that his barlow system works for him. Can't argue with that, if that's Bruce's thinking. 

 

I will have to make a similar decision for the ES92s. Do I want to sacrifice sharp stars at the edge so I can use a screw-in type barlow lens? I don't know that I do. 

[SeattleScott]

I used a 31 Nagler without coma corrector at F4.3 once. The central 2/3 was pretty good, but the outer 1/3 was pretty distracting. I don’t imagine a hyperwide at F4.5 would be any better. And while a barlow can clean up some things, my understanding is it doesn’t do anything for coma.

Now if one is just looking at small targets like galaxies and globulars, they can always back off the eyepiece and cut off the messy edge. Certainly that’s what I would do if I was using hyperwides in a fast Dob without coma corrector. Of course, then a 17 Ethos becomes the equivalent of a big, heavy, expensive 17 Delos. Just one without a field stop. But one could take advantage of the wider view for target acquisition when swapping eyepieces. The target might still be recognizable in the outer field. Then just center it up and back off the eyepiece to improve the aesthetics. Certainly not for everyone, but that would be an advantage of an Ethos compared to a Delos in a fast Dob without coma corrector. Most people probably wouldn’t pay up just to help with target acquisition. But if cost is no object and one doesn’t mind big eyepieces, I could see it.

[Starman1]

I used a 22mm Nagler from 1998-2010 (without glasses), a 21mm Ethos from 2010-2020, and a 22mm Nagler again from 2020-now (with glasses).

 

I forgot about the 22mm during the E21mm time, but used it again for a week in Australia in 2014 and remembered why I liked the eyepiece so much.

 

Scopes used: 8" f/10 SCT, 12.5" f/5.75 dob (the f/ratio with Paracorr 1 from 2004-2010, Paracorr 2 from 2010 to now), Tele Vue NP101 f/5.4 apo, and ES 102ED f/7 triplet apo.

 

Some comments:

 

21mm Ethos

--noticeably wider field than the 22mm.  True field 16.4% wider.

--much less eye relief than the 22mm (no glasses use).

--some astigmatism at the field edge (but small).

--Definitely needs a coma corrector.  Otherwise, star images are poor in 75% of the field.

--great contrast.

--darker background had me prefer it to the 31mm Nagler 99% of the time.

--star images a trace softer than the 17mm Ethos, but still excellent.

--weight 1021g

 

22mm Nagler

--a lot of eye relief.  Eyeguard must be pulled up a few clicks when not used with glasses.

--some astigmatism at field edge (but small) noticed in the dobs and the refractors.

--tried briefly without a Paracorr, but this eyepiece MUST have a Paracorr to yield good star images in a flat field in a dob/newtonian.

--great contrast, but background appears a bit brighter than the 21mm Ethos (4.8% difference in magnification?).  Image appeared washed out in the NP-101 due to the very low power (25x).

--a truly comfortable eyepiece to use, with or without glasses.

--star images a trace softer than the 17mm Ethos, but still excellent.

--star images were a bit sharper in outer field in the NP-101 and with the Paracorr 2 in the dobs.

--defines "immersion" in the field.  The large field size, combined with the comfort of use (I've compared it with an old pair of sneakers that disappear when on your feet), just involve you with the field in a way few other eyepieces match.

You can literally forget you're looking through an eyepiece and just become involved with the view.  In comparison, the 17mm T4 and 12mm T4 have nowhere near the same feel.  With them, you always know you're looking through an eyepiece.

--weight 681g.

 

Conclusion:  I'd still be using the 21mm Ethos but for the need for glasses at the scope, but it is a tiny sacrifice to have to use the 22mm Nagler in its place.

[JeremySh]

I used a 22mm Nagler from 1998-2010 (without glasses), a 21mm Ethos from 2010-2020, and a 22mm Nagler again from 2020-now (with glasses).

 

I forgot about the 22mm during the E21mm time, but used it again for a week in Australia in 2014 and remembered why I liked the eyepiece so much.

 

Scopes used: 8" f/10 SCT, 12.5" f/5.75 dob (the f/ratio with Paracorr 1 from 2004-2010, Paracorr 2 from 2010 to now), Tele Vue NP101 f/5.4 apo, and ES 102ED f/7 triplet apo.

 

Some comments:

 

21mm Ethos

--noticeably wider field than the 22mm.  True field 16.4% wider.

--much less eye relief than the 22mm (no glasses use).

--some astigmatism at the field edge (but small).

--Definitely needs a coma corrector.  Otherwise, star images are poor in 75% of the field.

--great contrast.

--darker background had me prefer it to the 31mm Nagler 99% of the time.

--star images a trace softer than the 17mm Ethos, but still excellent.

--weight 1021g

 

22mm Nagler

--a lot of eye relief.  Eyeguard must be pulled up a few clicks when not used with glasses.

--some astigmatism at field edge (but small) noticed in the dobs and the refractors.

--tried briefly without a Paracorr, but this eyepiece MUST have a Paracorr to yield good star images in a flat field in a dob/newtonian.

--great contrast, but background appears a bit brighter than the 21mm Ethos (4.8% difference in magnification?).  Image appeared washed out in the NP-101 due to the very low power (25x).

--a truly comfortable eyepiece to use, with or without glasses.

--star images a trace softer than the 17mm Ethos, but still excellent.

--star images were a bit sharper in outer field in the NP-101 and with the Paracorr 2 in the dobs.

--defines "immersion" in the field.  The large field size, combined with the comfort of use (I've compared it with an old pair of sneakers that disappear when on your feet), just involve you with the field in a way few other eyepieces match.

You can literally forget you're looking through an eyepiece and just become involved with the view.  In comparison, the 17mm T4 and 12mm T4 have nowhere near the same feel.  With them, you always know you're looking through an eyepiece.

--weight 681g.

 

Conclusion:  I'd still be using the 21mm Ethos but for the need for glasses at the scope, but it is a tiny sacrifice to have to use the 22mm Nagler in its place.

OK I’ll bite, Don.

What was the 1% of instances you preferred the N31 to the E21?