20mm eyepiece opinion. (Maybe 21)

[bomberbaz]

I am looking for user reviews and/or opinions on the eyepiece listed below. All 20mm bar the Ethos but the rationale for that is it offers an ideal exit pupil and not forgoing my FOV which I enjoy so much with the Nikon's.

20 or 21mm is set in stone. Primarily going to be used as an EP for nebula viewing with OIII filter. Recent trip highlighted this gap when objects that had been bright when I used the 12" were actually dimmer in the 17 Nikon. Further investigation showed the 3.5mm exit pupil was almost certainly at least partially to blame and so I aim to plug this gap. A 20mm eyepiece gives me 4.1 exit pupil and a 21mm provides one at 4.3.

I have already checked each eyepiece has a minimum (for me) 15mm ER, I am looking for reports/views/thoughts on comfort of use, flatness of field, off axis stars and my other thought is cost for something that will get limited use.

Ideally I would prefer a 21mm eyepiece but after a good long look I only found hyperions (no thanks), Denkmeier (can't source) & Ethos. (How much) The cost is the main stalling issue with the Ethos, even 2nd hand is probably more than I really want to shell out. Although any other suggestions would be welcome.

For the 20mm, the researched list is:

1. ES 62 series 
2. ES 68 series
3. StellaLyra UWA 
4. Pentax XW

I am also considering this Svbony Wide Angle Eyepiece 1.25" Telescope Eyepiece 20mm FMC 68 Degree Astronomy Eyepiece for Telescope (20mm): Amazon.co.uk: Electronics & Photo does anyone own one, feedback would be great. I already own the 6mm which is very good and this would be a very low cost way of filling the gap, I also have a 3 month window to try it out. 

Edited August 11, 2022 by bomberbaz

[globular]

If you want an Ethos 21mm, have you thought about the APM XWA 20mm 100 degree eyepiece?  It has 15mm eye relief and seems to get good reviews.
Sorry to extend your list. 🙃

 

[Louis D]

6 hours ago, bomberbaz said:

I am also considering this Svbony Wide Angle Eyepiece 1.25" Telescope Eyepiece 20mm FMC 68 Degree Astronomy Eyepiece for Telescope (20mm): Amazon.co.uk: Electronics & Photo does anyone own one, feedback would be great.

See my thoughts in the thread below:

Long story short, you wouldn't like it in your 12" scope.

[Louis D]

The StellaLyra UWA 20mm might be your best bet for long eye relief and excellent correction, possibly better than the APM XWA 20mm.  I've been happy enough with my 22mm NT4 to not feel tempted to buy one to find out first hand, though.

Here's a report on one here on SGL:

 

[F15Rules]

I've owned two on your list, the Pentax 20mm XW and the ES 20mm 68degree..

I didn't like the Pentax 20mm (significant Field Curvature) and much preferred the Vixen LVW 22mm (not in your 20/21mm stipulation and rare as Hens Teeth).

The ES 20mm 68 is a fine, well built eyepiece with good optics.

Dave

[Guest]

The Stellalyra is a Long Perng eyepiece.  I own the same eyepiece with Orion branding.  There is no other way to say it, this is a good eyepiece.  One of the posts above directs you to a thread specifically about this eyepiece and really nothing more needs to be added here.  All I will say is it is definitely worth the money and i have no regrets buying it. 

[bomberbaz]

9 hours ago, Louis D said:

The StellaLyra UWA 20mm might be your best bet for long eye relief and excellent correction, possibly better than the APM XWA 20mm.  I've been happy enough with my 22mm NT4 to not feel tempted to buy one to find out first hand, though.

Here's a report on one here on SGL:

 

Thanks for drawing my attention to that @Louis D, very good report and just what I was looking for. Also the report on the Svbony. My current 6mm  Svbony is used in my F12 refractor, so experience of it is basically with a 0.5 exit pupil in a very slow scope.

Re the Svbony, at £40 Uk you basically get what you pay for in terms of results, I'll pass this time. 

Much obliged

Steve

[Louis D]

As I say in this post in my Svbony 20mm thread, they do make for a excellent pairing in a binoviewer at long f-ratios, so keep that in mind.  You're not going to be able to pair up the StellaLyras in a 1.25" binoviewer. 😁

[cajen2]

To get more than 'you pay for in terms of results', consider a Vixen NPL 20mil, assuming its narrow FOV doesn't bother you. Best value for money range out there.

[Louis D]

18 minutes ago, cajen2 said:

To get more than 'you pay for in terms of results', consider a Vixen NPL 20mil, assuming its narrow FOV doesn't bother you. Best value for money range out there.

How well does the Plossl design of the NPL hold up at sub-f/5 focal ratios in your experience?  Tele Vue's Plossls are modified with slightly concave outward facing surfaces to get better correction at shorter focal ratios:

[cajen2]

I haven't tried the whole range, but my 30mil is a little gem, with sharp images across most of the FOV. I use it as my 'finder' EP. It's a wonder at £41. Used in my f/5 and f/6 dobs, it's fine.

Edited August 12, 2022 by cajen2

[Carl Au]

I have the 20 mm ES from the 68 series. I run mine in a 4 inch fl7 apo and have no complaints, think TV Panoptic, but much cheaper.... 

[Ags]

Very happy with my ES 20/68 too.

[Zeta Reticulan]

9 hours ago, Louis D said:

How well does the Plossl design of the NPL hold up at sub-f/5 focal ratios in your experience?  Tele Vue's Plossls are modified with slightly concave outward facing surfaces to get better correction at shorter focal ratios:

In my experience, the only discernible differences between TV Plossls and NPL's are ergonomics, build quality, and focal lengths. 

 

 

[Louis D]

14 hours ago, Zeta Reticulan said:

In my experience, the only discernible differences between TV Plossls and NPL's are ergonomics, build quality, and focal lengths. 

 

 

And price. 😆

[Zeta Reticulan]

40 minutes ago, Louis D said:

And price. 😆

Oh yeah, and that. lol

[Stu]

On 11/08/2022 at 17:30, globular said:

If you want an Ethos 21mm, have you thought about the APM XWA 20mm 100 degree eyepiece?  It has 15mm eye relief and seems to get good reviews.
Sorry to extend your list. 🙃

 

What he said ^^^. I’ve had a couple and they are excellent. Not a bad price either.

[bomberbaz]

On 11/08/2022 at 17:30, globular said:

If you want an Ethos 21mm, have you thought about the APM XWA 20mm 100 degree eyepiece?  It has 15mm eye relief and seems to get good reviews.
Sorry to extend your list. 🙃

 

23 hours ago, Stu said:

What he said ^^^. I’ve had a couple and they are excellent. Not a bad price either.

Ok thanks you two, it would make a great eyepiece but this thread has made me think a little deeper and now I am questioning myself about how much use this (20/21mm) eyepiece is likely to get. At first I was telling myself as above that it would be mainly for OIII filter use but the more i think about it, I am wondering if the FOV and exit pupil of this sized EP will have a greater range of applications making it more compelling to consider a more expensive option, maybe even the 21mm Ethos, which to my OCD is a better solution. A re-visit to old observing lists should help highlight things a little better. 

And I think my impatience is less commanding within me than it used to be and therefore a trial test run using an old 20mm plossl I have and comparing notes against the 17mm Nikon will help me decide. By no means do I expect the 20mm to outshine the Nikon in any areas, other than that is brightness of nebula through the OIII due to increased exit pupil. This is the main concern, all other things are for pondering after the test.

Well this is another hornets nest that's be woken up and might yet sting me where it hurts! (read empty wallet)

cheers all

Steve

[Mr Spock]

If you can find one, a 20mm T5 Nagler would be a great choice.

[Guest]

I use my 20mm quite frequently actually.  I find it really good for clusters and such. Here is an example of a couple things and roughly how they may look.  This is through my scope so your milage may vary.  This is the Orion Nebula and the Pleaides.  I think they are framed very nicely. 

[Don Pensack]

The Pleiades benefits from a 2.5-3° field:

https://science.nasa.gov/pleiades-seven-sisters-star-cluster

The "dipper" shape is only about the center 50° of the cluster.

Best view ever: 80mm refractor at 15x.  Nebulosity everywhere, even way outside the cluster.

Though, if you are looking for details in, say, the Merope nebula (near star 23), that magnification is great.

[Louis D]

1 hour ago, Mr Spock said:

If you can find one, a 20mm T5 Nagler would be a great choice.

 

On 11/08/2022 at 11:07, bomberbaz said:

I have already checked each eyepiece has a minimum (for me) 15mm ER

TV eyepiece specs for 20mm NT5 (see the column right of C, 12mm ER):

EN5-20.0

20

Nagler 5 (disc)

2"

6 / 4

82

C

12

27.4

2.1

1.3

2.1

0.15

1.04 / 16.6

Y*

So, not a good choice for the OP who seeks a minimum of 15mm eye relief.  I was going to recommend it myself until I checked TV's specs and ruled it out.