20 to 25mm - the all-purpose focal length?

[25585]

Reviewing my collection, I realise that 20 to 25mm eye pieces are the most useful and used focal length. 

Wide field versions available, all designs - huge Ethos to small Plossl, can be barlowed to 10 or even 5mm. Made in both 1.25 & 2 inch fits. Good for bino viewers. 

So what 20-25mm eps do you own and use?

 

[drjolo]

I think it is more related to exit pupil of observing setup. I have ES 24mm 68*, but I do not use it much. With my ACF 10" telescope I use more often 40mm SWAN, 31mm Aspheric, and for higher magnifications 18 and 10mm orthos. These last three I also use with my 100/600 mobile refractor. 

[Paz]

I've got a 25mm plossl that came with my st120 and 26mm plossl that came with the mc127, but they don't get used much because I have a 25mm slv which I prefer.

The 25mm slv probably sees most use in the mc127 looking at the moon and sun in poorer seeing conditions. I've also got a 20mm slv, that also gets a lot of use in all my small scopes (small meaning anything except the vx14!).

I've a 22mm Nagler for use with the vx14, which is right up there as one of my favourite eyepieces, great for open clusters or even full disk lunar observing.

I don't tend to use barlows, I just prefer not to, but on the topic of flexibility I've recently acquired a 24-8mm zoom eyepiece and whilst the quality of views doesn't match my fixed eyepieces the zoom eyepiece is actually growing on me as a really flexible and easy to use and sometimes making the difference between me choosing to go out or not for shorter sessions.

[Saganite]

Here are mine Richard, like them all and use them in my three scopes. The 24 Panoptics get by far the most use,in my binoviewer, in each scope, giving superb sharpness and FOV.

The TAL Gen II 25mm Plossl, I have had the longest time and ties with the UO Optics 25mm for position of favourite, never to be parted with.

The  Celestron Ultima 24mm, I have had for just a few days and not yet used, but its status and quality are beyond question, so another keeper, mainly for my 4" frac I think.

The 25mm Zebra plossl is another fine optic which gets some use .

The Fullerscopes 20mm is an early and inexpensive 82 deg plossl, which I have had only a few months, but absolutely love it in the 5" f15 frac.

Last but not least is the Orion Ultrascopic 20mm, a really lovely eyepiece, again mainly for my 4"- I like to use small oculars in this scope.

Overkill in this focal area certainly, but I get pleasure owning and using them all.

 

[DirkSteele]

Arguably the Zeus on the Mount Olympus of eyepieces, the 21mm Ethos.  When I am travelling and need to keep the weight down, its little cousin the 24mm Panoptic.

[Littleguy80]

Currently my most used EP is the ES68 24mm. Great finder EP and large exit pupil when using filters on diffuse nebulae. I’ve just bought a Lunt HDC 20mm which I think will ultimately replace it. The ES still offers a larger exit pupil over the Lunt but I think the Lunt will have it beat in every other respect. 

As others have said, it’s more a question of the scope in use when it comes to the question of most used focal lengths. 

[BGazing]

Pan 24, bought used. Incredibly sharp. Galaxies and smaller open clusters in C8, widefield (including with filters) in refractors.

Had ES24, it was excellent, too, a bit more comfy due to eye relief, but went for Pan24 because it very lightweight and easier to balance on refractors.

 

 

[mikeDnight]

Currently I've only got one 20mm eyepiece, a Vixen Lanthanum. It's nice but not as sweet as my 25mm TV plossl which is a very nice eyepiece. My favourite eyepiece, close to the 20mm under discussion, is a 18mm Celestron Ultima. This is one of those dream eyepieces that once obtained, you wouldn't sell for love nor money! 

[Moonshane]

I have 2x 20mm TV Plossls, 2x 25mm TV Plossls plus a 24mm Panoptic (and a 19mm/27mm Panoptic - just outside the parameters). So yes, I agree, it's a great focal range for eyepieces.

[25585]

I have a pair of Vixen LVW 22, pair of Vixen LV 20mm, 20mm Erfle, Celestron 25mm Plossl, Bresser 25mm Plossl, Baader 25mm Symmetrical Plossl in 1.25 and Celestron Ultima LX 22mm + Orion LER Lanthanum LHD 20mm in 2 inch fit. 

Seems to be a popular FL to include with new scopes, especially Plossls. Scopes are sold on, the eps remain. 

[25585]

3 hours ago, Saganite said:

Here are mine Richard, like them all and use them in my three scopes. The 24 Panoptics get by far the most use,in my binoviewer, in each scope, giving superb sharpness and FOV.

The TAL Gen II 25mm Plossl, I have had the longest time and ties with the UO Optics 25mm for position of favourite, never to be parted with.

The  Celestron Ultima 24mm, I have had for just a few days and not yet used, but its status and quality are beyond question, so another keeper, mainly for my 4" frac I think.

The 25mm Zebra plossl is another fine optic which gets some use .

The Fullerscopes 20mm is an early and inexpensive 82 deg plossl, which I have had only a few months, but absolutely love in the 5" f15 frac.

Last but not least is the Orion Ultrascopic 20mm, a really lovely eyepiece, again mainly for my 4"- I like to use small oculars in this scope.

Overkill in this focal area certainly, but I get pleasure owning and using them all.

 

One in the middle looks interesting Steve, flush eye lens reminds me of Brandon eps, it's got that clear lens look. 

[John]

I have a number of EP's in this focal length range as well:

24mm Panoptic

21mm Ethos

25mm BST Starguider

21.5mm - 7.2mm zoom

I generally find these focal lengths more useful for DSO hunting than my 31mm Nagler because they deliver a slightly darker background sky. Under a really dark sky the 31mm Nagler becomes a favourite again.

Just outside the parameters on the shorter side I have the Delos 17.3 mm which I enjoy using a lot too.

In terms of an all purpose eyepiece, the zoom obviously is very versatile although the AFoV is barely 40 degrees at the 21.5mm setting. I had a great outreach night with the 12" dob a short while back when all I needed was my 13mm Ethos. 122x was enough power for double stars, stunning whole moon views and resolving brighter globular clusters while the .82 degree true field was big enough for open clusters and some DSO pairings. 

 

[Saganite]

17 minutes ago, 25585 said:

One in the middle looks interesting Steve, flush eye lens reminds me of Brandon eps, it's got that clear lens look. 

The TAL Gen II 25mm, really lovely eye piece, sharp as you like with a deep purple colour.

[Doc]

I use a 20mm & 25mm Clave' of Paris eyepieces.

[Saganite]

A single mm outside the given parameters but much used, and classic Japan made 5 element Pseudo- Masuyama oculars.

[Louis D]

I don't tend to use that range all too often because I tend to jump from 30mm to 40mm up to 10mm to 17mm pretty quickly.

I do have a 20mm generic reversed Kellner, 20mm Orion centering SWA, 22mm AstroTech AF70, 23mm aspheric 62 degree, 20mm to 24mm with an 8-24mm Celestron Regal zoom, 25mm Meade HD-60, 26mm Orion Sirius Plossl, 27mm TV Panoptic, and a 28mm Edmunds RKE.  For monoviewing, I probably use the AF70 the most of those due to its well corrected, wide field of view.  Many of those listed are paired for binoviewer usage because the barlow nosepiece multiplies them up by over 2x into the mid-teens range that I like to observer at.

[Littleguy80]

1 hour ago, John said:

I generally find these focal lengths more useful for DSO hunting than my 31mm Nagler because they deliver a slightly darker background sky. Under a really dark sky the 31mm Nagler becomes a favourite again

Do you find you prefer the Nagler when using a UHC/OIII filter? 

[iPeace]

I've owned the 21 Ethos and the 25 TV Plossl. Had two ES 24/68's. Currently have the 18.2 DeLite, the 19 Panoptic and two 24 Panoptics - three, with the latest incoming...

Almost forgot the two 8-24 Baader Zooms I still have, and the Pentax 8-24 Zoom I once had...

[Stu]

I struggle with these types of questions sometimes because it totally depends upon the type, and most specifically the focal ratio of your scope as to whether this focal length eyepiece is useful or not.

If you take f6 as a rough average then it does lead to some comments which are comparable. In the past I have used Maks at f20, and currently have f14 which lead to a very different exit pupil and different usefulness. Trying to relate the value of a 20 ish mm eyepiece in an f20 8” Mak with an f3.7 20” dob can lead to confusion....  

That said, and in a spirit of not being (too) awkward  I do have a 24mm Panoptic which is a wonderfully sharp eyepiece giving me around 3mm exit pupil in the Tak, x30.

I also use two 25mm Zeiss converted microscope eyepieces which I use in a Mark IV Binoviewer for white light solar and also astro targets, mainly lunar where they allow me to use high powers without floaters being a problem. Ironically I rarely use them at native focal length, but normally barlow the socks off them to get down to anything around a 3.5mm effective focal length. They are very sharp, with low scatter, a nice big exit lens and good eye relief and barlow incredibly well. Amazing eyepieces.

I have owned a 21mm Ethos in the past, ‘nuff said, lovely and as John says generally giving a nicer contrast than the 31mm Nag unless under pristine skies. Also the 20mm ES 100 degree is excellent. Never had the chance to side by side them but I doubt there is too much in it. With prices as they are currently I would be ES all the way, although the Lunt has an excellent reputation and is great value, so is probably worth a try.

[Timebandit]

 

Eyepiece's which I mainly use are a 20mm nagler and 10mm XW Pentax

In the range 20/25 I only have one eyepiece?, but I find this works fine for what I need. Also IMO a great quality eyepiece. The Televue nagler 20mm T5 I find works lovely in the 14" OOuk and 8" OOuk for my DSO hunter. This provides enough magnification to enable these DSO fussys to be located, with the benefit of a great fov 82d. The quality of the optics are top class IMO and so good I have never really thought that I was missing anything by not going up to an Ethos. The only thing I may miss if i bought an Ethos is money in my pocket, a big empty pocket? . IMO the nagler 20mm T5 really takes some beating?

 

 

[Stu]

18 hours ago, Littleguy80 said:

Do you find you prefer the Nagler when using a UHC/OIII filter? 

Sorry to interject. I just wanted to relay a tale from SGL10 when I was observing with Faulksy and Swampthing using Mike’s 14” (how times change!) and my 16”(ditto!). Steve’s 20” had succumbed to dew unfortunately.

Most of the time, the 21mm Ethos was giving the best views using both OIII and UHC filters. However, on the Crescent Nebula, the 31mm Nag definitely had the edge. Probably an effect of exit pupil but it just shows that it is worth trying these things out as the results may surprise.

[John]

19 minutes ago, Littleguy80 said:

Do you find you prefer the Nagler when using a UHC/OIII filter? 

Hi Neil,

For the Veil Nebula and other highly extensive nebulae, yes the 31mm Nagler is the tool I choose. For most other DSO's, the 21mm or 13mm Ethos are my mainstays with the 8mm Ethos being very useful for confirming smaller planetary nebulae.

In all honesty I don't use the 31mm Nagler all that much but there are a few things that it is unrivalled for.

[Littleguy80]

Just now, John said:

Hi Neil,

For the Veil Nebula and other highly extensive nebulae, yes the 31mm Nagler is the tool I choose. For most other DSO's, the 21mm or 13mm Ethos are my mainstays with the 8mm Ethos being very useful for confirming smaller planetary nebulae.

In all honesty I don't use the 31mm Nagler all that much but there are a few things that it is unrivalled for.

Thank you, John. I had a similar conversation with Gerry recently on the ES82 30mm. Great for a small number of objects but in most cases something like the Ethos 21mm or Lunt HDC 20mm is the tool of choice  

[Littleguy80]

3 minutes ago, Stu said:

Sorry to interject. I just wanted to relay a tale from SGL10 when I was observing with Faulksy and Swampthing using Mike’s 14” (how times change!) and my 16”. Steve’s 20” has succumbed to dew unfortunately.

Most of the time, the 21mm Ethos was giving the best views using both OIII and UHC filters. However, on the Crescent Nebula, the 31mm Nag definitely had the edge. Probably an effect of exit pupil but it just shows that it is worth trying these things out as the results may surprise.

Thank you, Stu. I have to admit to being surprised by that. I've not seen the Crescent nebula yet but I believe it's a relatively small target and hence thought it would be better at higher mags. Which, in retrospect, is a flawed way to think about it!

[John]

The Crescent Nebula (NGC 6888) is around 1/3rd of a degree across I think. A reasonably large object.