6mm eyepiece - Vixen SLV or Fujiyama Ortho?

[Neil Mack]

Looking for a 6mm eyepiece for planetary and double star stuff.

Instinct and habitat would generally make me go for the orthoscopic; but there are good reports of the SLV, and its high eye relief might be welcome in a short focus eyepiece.  John Huntley's review suggested that the Vixen 6mm compared very favourably to the BGO 6mm, and the general view is that the Fujiyama and BGO ortho  ranges are similar in quality.

 

But has anyone actually directly compared the Vixen and Fujiyama?

[Chris]

I used to be really into the classic ortho, but now days the honest truth is I'd rather have my eye pressed against something with decent ER and a nice soft eyecup which cut's out stray light. I think I'd say the same if the SLV's weren't quite as good as say a BCO, BGO, or fujiyama, but they are as good....and very comfy just to re-iterate  

I've not directly compared the 6mm SLV to a 6mm fujiyama, but I own a 6mm SLV, and have previously owned the 6mm BCO, 6mm circle T (or was it 7mm?), and a 5mm BGO. 

I directly compared my 6mm SLV with a well regarded 6.3mm Vixen Plossl the other day, the vixen is a good example of a Plossl but the SLV definitely had less scatter and a slightly more neutral perhaps brighter tone I thought...really nice!  

[Charic]

I haven't tried either of the EP's you mention, but I have  the William Optics SPL, another one to consider for planetary work, good eye-relief too.
I also have some Baader classics, not sure about those just yet either?

[Alan White]

I have both a SLV 6mm and a Baader 6mm BCO and have compared both.

Very similar performance on most targets, if not all, nice eye relief on the SLV and very tight eye relief on the BCO, but the BCO is a minuscule bit sharper on planets sometimes in poorer conditions.

But like Chris Lock has said, comfortable eye relief wins out in my book as well.

I must add a big SLV fan as my ep case is full of them.

As they used to say on Blind Date 'the choice is yours'.

[Paul73]

SLV for me. The BCO is a very sound performer, but it feels like I'm about to be stabbed in the eye the whole time. I believe that the BGO is only 40° fov.

The 6mm SLV is at least on par with the 6mm Delos for planetary, lunar and doubles. I've been having a bit of a comparison over the last few weeks having recently acquired the Delos. Sadly the SLV is on its way to a new home. I couldn't split the two on performance, but the wider feeld and better ergonomics of the Delos swayed it.

Paul

[F15Rules]

Hi Neil,

The BCO orthos are excellent, (and have an artificially widened 50deg fov compared to a BGO and most other orthos at 40-42deg - the 50deg is sharp across the vast majority of the field at F7 or so), but they do have short eye relief. The best orthos I have ever used, bar none, were Antares HD orthos (not to be confused with standard Antares orthos) - absolutely superb optically. Julian (Nightfisher) bought one from me (a 7mm I believe) and loves it too.

The SLVs I believe have 20mm eye relief across the range.

If you really like orthos, I would recommend a 12.5mm for extra eye relief, and use a x2 barlow to give you an effective 6.25mm eyepiece. Althernatively, I also recommend Takahashi LE eyepieces, and they offer a 12.5mm version which with a x2 barlow would get you very close to your target 6mm. They are small and lightweight, around 100g in 1.25" barrel.

If you don't mind the additional weight, I'd also highly recommend the Vixen LVW, although they don't do a 6mm, it's either 5mm or 7mm, or Pentax XW (same focal length availability as LVW).

I also use a nice Pentax XL 10.5mm with a threaded lens assembly unscrewed from a x2 barlow, this then operates at x1.6 thus giving me c6.5mm equivalent. But again a larger, so heavier, unit.

Good luck,

Dave

 

 

[Louis D]

If you ever come across a used 5.2mm Pentax XL, they provide excellent performance for about 2/3rds the cost of a used Delos or XW.  Side by side, the only difference I've noted is a slightly brighter background probably due to more modern multicoatings in the later two.  The 5.2mm does an excellent job breaking up globulars and doubles, and is absolutely sharp edge to edge to at least f/5.

[Paz]

+1 for slvs - I've got a set of slvs for use with my small scopes and am very happy with them.

[michael.h.f.wilkinson]

+1 for the SLVs from me too. I have two SLVs (5 and 15mm) and they are excellent. The XW 5 I also have has a much bigger FOV, but the SLV5 matches it for sharpness, I feel. More visual comfort also means you can spend more time at the EP without fatigue, allowing you to tease out more detail, I find.

What I really don't buy is that a longer focal length orthoscopic with Barlow  to increase eye relief would be better than using designs like the SLV, Delos, XW, or any planetary EP, which consist of a Smyth lens (= matched (!) Barlow) followed by a group of lenses that essentially form a regular EP. After all, the key advantage that the Abbe orthoscopic design has over planetary EPs is the small number of glass/air interfaces, which can reduce internal reflections and scatter. By adding a Barlow, you increase the number of interfaces in exactly the same way the planetary designs do, without the benefit of matching the lenses.

[Louis D]

3 hours ago, michael.h.f.wilkinson said:

+1 for the SLVs from me too. I have two SLVs (5 and 15mm) and they are excellent. The XW 5 I also have has a much bigger FOV, but the SLV5 matches it for sharpness, I feel. More visual comfort also means you can spend more time at the EP without fatigue, allowing you to tease out more detail, I find.

What I really don't buy is that a longer focal length orthoscopic with Barlow  to increase eye relief would be better than using designs like the SLV, Delos, XW, or any planetary EP, which consist of a Smyth lens (= matched (!) Barlow) followed by a group of lenses that essentially form a regular EP. After all, the key advantage that the Abbe orthoscopic design has over planetary EPs is the small number of glass/air interfaces, which can reduce internal reflections and scatter. By adding a Barlow, you increase the number of interfaces in exactly the same way the planetary designs do, without the benefit of matching the lenses.

Agreed.  I've compared barlowing longer focal length eyepieces to native focal length XLs, XWs, and Delos, and the native ones win even when using good quality barlows.  The eyepiece designers took the time to match the lenses and to carefully baffle and blacken everything to maximize contrast and sharpness.  Coupling a barlow to an eyepiece just can't match this level of thoughtful integration.

[Piero]

+ 1 for the SLV. Very nice eyepieces in a small light package. I compared several times against the Delos, and they were on par except for the fov and a marginal colour tint difference (the SLV were slightly more neutral to my eye). 

Highly recommended, particularly if weight is a concern. 

 

--------------

 

Regarding the argument that a lower focal length orthoscopic with barlow can or cannot deliver better views that a SLV/Delos/XW which consist of a Smyth lens (=matched (!) Barlow), I think that things are more complicated that that.

Of course people are free to disagree, but what follows comes from my experience at least:

I am not convinced that the matching glass automatically delivers optimum views. Instead I believe that each glass layer has its own level of transmission and the resulting transmission is largely affected by the transmission / light scattering / colour tint of the worst level.

One example: Docter 12.5mm vs Delos 12mm +/- Powermate 2.5x or +/- Baader VIP 2.0x

Without barlow/telextender, the Docter 12.5mm went deeper and showed less light scattering than the Delos 12mm on planetary targets (+ solar) and DSO. This was repeated so many times that I lost the count. The differences were small of course (not a black / white!) but they were there, with subtle details popping up in the Docter. For giving a palpable feeling, to me it was a bit like the difference I noticed when comparing my Naglers 13mm and 7mm against Delos 12mm and 8mm. Coming back to us, when the powermate 2.5x was added (I think I can assume that this element is a matching glass with the Delos), the gap between these two eyepieces was basically 0. While there was no image degradation with the Delos 12mm, the Docter 12.5mm lost quality to my eye. How much? Well, it was basically identical to the Delos 12mm + PM2.5x. I couldn't tell the difference between the two in terms of optical performance. Instead, when the Baader VIP 2.0x was added, the Docter didn't lose any performance. The Delos 12mm actually improved a bit (due to the longer cone of light I suppose), but it was still behind the Docter. 

I repeated the same tests using my Vixen SLV 9mm + Baader VIP configured to give about 5mm focal length against the Docter 12.5mm + Powermate 2.5x. Comparable views. Instead, when I used the VIP + the Docter, again the Docter won. 

I tested my Zeiss zoom + powermate 2.5x, and again, the zoom lost the advantage that it normally has on axis against SLVs. When the VIP was used, the advantage was restored. 

So, my conclusions based on tests using my eye are that: 

- less glass may be better, but if the glass has very high transmission and excellent light scatter control, this difference is negligible

- matching glass of the barlow / Smyth element is not all. If the transmission and light scatter control of this element are lower than the other glass layers, the view is "compromised". This does not mean that the view is bad, but there is a loss in resolution

- following the previous point, if the long focal length orthoscopic + barlow use glass that has higher transmission and light scatter control than a corresponding shorter focal length eyepieces (e.g. XW/SLV/Delos), I would not be surprised that the previous combination goes a bit deeper than the latter. 

[michael.h.f.wilkinson]

16 hours ago, Piero said:

+ 1 for the SLV. Very nice eyepieces in a small light package. I compared several times against the Delos, and they were on par except for the fov and a marginal colour tint difference (the SLV were slightly more neutral to my eye). 

Highly recommended, particularly if weight is a concern. 

 

--------------

 

Regarding the argument that a lower focal length orthoscopic with barlow can or cannot deliver better views that a SLV/Delos/XW which consist of a Smyth lens (=matched (!) Barlow), I think that things are more complicated that that.

Of course people are free to disagree, but what follows comes from my experience at least:

I am not convinced that the matching glass automatically delivers optimum views. Instead I believe that each glass layer has its own level of transmission and the resulting transmission is largely affected by the transmission / light scattering / colour tint of the worst level.

One example: Docter 12.5mm vs Delos 12mm +/- Powermate 2.5x or +/- Baader VIP 2.0x

Without barlow/telextender, the Docter 12.5mm went deeper and showed less light scattering than the Delos 12mm on planetary targets (+ solar) and DSO. This was repeated so many times that I lost the count. The differences were small of course (not a black / white!) but they were there, with subtle details popping up in the Docter. For giving a palpable feeling, to me it was a bit like the difference I noticed when comparing my Naglers 13mm and 7mm against Delos 12mm and 8mm. Coming back to us, when the powermate 2.5x was added (I think I can assume that this element is a matching glass with the Delos), the gap between these two eyepieces was basically 0. While there was no image degradation with the Delos 12mm, the Docter 12.5mm lost quality to my eye. How much? Well, it was basically identical to the Delos 12mm + PM2.5x. I couldn't tell the difference between the two in terms of optical performance. Instead, when the Baader VIP 2.0x was added, the Docter didn't lose any performance. The Delos 12mm actually improved a bit (due to the longer cone of light I suppose), but it was still behind the Docter. 

I repeated the same tests using my Vixen SLV 9mm + Baader VIP configured to give about 5mm focal length against the Docter 12.5mm + Powermate 2.5x. Comparable views. Instead, when I used the VIP + the Docter, again the Docter won. 

I tested my Zeiss zoom + powermate 2.5x, and again, the zoom lost the advantage that it normally has on axis against SLVs. When the VIP was used, the advantage was restored. 

So, my conclusions based on tests using my eye are that: 

- less glass may be better, but if the glass has very high transmission and excellent light scatter control, this difference is negligible

- matching glass of the barlow / Smyth element is not all. If the transmission and light scatter control of this element are lower than the other glass layers, the view is "compromised". This does not mean that the view is bad, but there is a loss in resolution

- following the previous point, if the long focal length orthoscopic + barlow use glass that has higher transmission and light scatter control than a corresponding shorter focal length eyepieces (e.g. XW/SLV/Delos), I would not be surprised that the previous combination goes a bit deeper than the latter. 

Essentially, we agree: less glass is better, but quality of coatings, glass, optical figure, etc are equally important. My statement should be read as meaning that individual Abbe ortho/Barlow (or other EP/Barlow/tele-centric) combinations may beat a particular planetary EP. However, If I design a Barlow well, but with no knowledge of the separately and  equally well designed EP, I cannot possible match them in such a way that the residual aberrations of the one compensate those of the other. I might be lucky, but I have no guarantees. By contrast, when designing an EP like the LV, Delos, XWs, or similar, using the same quality optical glass and coatings to match, I can design the Smyth lens in such a way that it compensates residual aberrations of the rest of the EP. I could in fact probably use fewer elements and groups, than when I design the best possible (APO) barlow coupled to the best possible EP. Just focusing on chromatic aberration: I would need a three element Barlow for full APO correction, whereas most Smyth lenses are doublets. This is made possible because the rest  of the EP can compensate for residual CA in the Smyth lens.

[jetstream]

22 hours ago, Piero said:

So, my conclusions based on tests using my eye are that: 

- less glass may be better, but if the glass has very high transmission and excellent light scatter control, this difference is negligible

- matching glass of the barlow / Smyth element is not all. If the transmission and light scatter control of this element are lower than the other glass layers, the view is "compromised". This does not mean that the view is bad, but there is a loss in resolution

- following the previous point, if the long focal length orthoscopic + barlow use glass that has higher transmission and light scatter control than a corresponding shorter focal length eyepieces (e.g. XW/SLV/Delos), I would not be surprised that the previous combination goes a bit deeper than the latter. 

I'm glad you mention this Piero, my observations and thoughts match yours. After talking to a few VIP owners there is the concensus that the VIP "sharpens" the views on many eyepieces and in no case hinders the performance. The VIP does not degrade DSO performance as long as the barlowed focal length matches the situation to my eyes, IMHO.

Whether the VIP offers less filtering by luck or by chance was a chance I was willing to take...

To the OP: many of the differences between eyepieces can be masked by mediocre seeing or optical systems below a certain level or the combination of both. You cannot go wrong with an ortho and the SLV's are highly regarded as well. Myself I love orthos.

[John]

Looks like a Baader VIP needs to be on my Christmas list

[Piero]

1 hour ago, jetstream said:

To the OP: many of the differences between eyepieces can be masked by mediocre seeing or optical systems below a certain level or the combination of both.

That's a very good point which is always worth stating. No very good seeing, no party. To spot differences the seeing must cooperate. Same for the telescope optics IMO, as you say.  

The other thing is careful observation. I remember some time ago John wrote a post describing how he observes Jupiter, the time he invests on it on a good evening to gradually catch faint details. Frankly, that was one of the most inspiring post about planetary observation I read  and it changed the way I observe these targets. Time, patience, and dedication at the eyepiece works also on DSO in my opinion, although aperture and dark skies are more crucial. 

Spotting 5%-15% differences in eyepieces also requires calm and dedicated observing. Casual observing will unlikely reveal something IMO.  

 

1 hour ago, John said:

Looks like a Baader VIP needs to be on my Christmas list

It's a lovely tool John and also a perfect match for a zoom like the Leica as you already know.  

 

 

To readers who are not aware of this barlow, the Baader VIP is not parfocal and requires a bit of inward travel (about 1" in my TV60 when configured at 1.5x or 1.76x). So if one doesn't mind this, there is no downside.

[michael.h.f.wilkinson]

Agreed tha time and patience are essential. Even on nights of so-so seeing there are moments of better seeing, so it pays to wait for such moments.

[Alien_Photons]

I have a 7mm LV and with respect to eye relife it is a very comfortable experience for long observing sessions. As a result it is the eyepiece I compare against for comfort. So I say the SLV.

I also have a 9mm Delite which on sharpness alone is noticeably better than the LV this matters on the planets. So if the Ortho is sharper then I say the Ortho.

On the subject of Barlows and the like I use the 9mm Delite with a 2.5 powermate which works well but not so with the LV. Its an added complication that a singular eyepiece avoids. So for the planets and the best views something to avoid given the chance. I wouldnt spend money on an ortho and a Barlow I would invest it all into the best eyepiece I could.

[John]

The SLV range are better optical performers than the original LV range IMHO.

 

[michael.h.f.wilkinson]

5 minutes ago, John said:

The SLV range are better optical performers than the original LV range IMHO.

 

Agreed. I had the LV 7 and 9mm, and they were good, but were ultimately ousted first by TV Radians (8 and 10mm), and later by Pentax XWs (7 and 10mm). The XWs had a small, but distinct edge over the Radians, the Radians had a small but distinct edge over the LVs, however, the SLVs I have perform very, very close to the XWs, in everything except FOV, so the SLVs are definitely better than the LVs (which are also very good indeed)