TS Planetary HR vs Vixen SLV

[Ags]

I do find eyepiece reviews so difficult. We can't see through other people's eyes. 

I also think the 4mm shootout I linked to above is limited by the high magnifications being used. I don't know what the seeing was like, but the reviewer does acknowledge that 4mm was pushing it on the night.

[John]

31 minutes ago, Ags said:

I do find eyepiece reviews so difficult. We can't see through other people's eyes....

 

I agree. When I used to do them it took hours of observing over several sessions before I would reach any conclusions.

And even then it could only be a report of what my eyes, my scopes and my skies and my brain were producing.

I did have an advantage that I had the eyepieces loaned to me so I had not paid for them out of my own pocket and also that FLO (who loaned me them) never sought to influence what I reported in any way at all.

There is no substitute for finding out for yourself though, if that can be arranged

 

[Ags]

@John I am thinking of our contrary feelings about the Nirvana 16mm. You say it is comparable to the equivalent Nagler, while I find it unacceptable. I suspect the reason may be my eyes are unable to compensate for the field curvature.

 

[johninderby]

Having owned a 16mm Nagler I find it’s very similar in performance to the 16mm Nirvana in most scopes. The Nagler might have a small advantage in a very fast scope though. Have found field curvature just isn’t an issue with the Nirvana. 

[Ags]

I know I am in the minority. It's either my eyes or my eyepiece. I should have sent the Nirvana 16 back at the time, but I really wanted to like it.

[johninderby]

I wonder if being near sighted or far sighted has something to do with it? 🤔

[Ags]

I am very short sighted and I have presbyopia too.

[johninderby]

Hmmm.....I’m far sighted. 🤔

[John]

22 minutes ago, Ags said:

@John I am thinking of our contrary feelings about the Nirvana 16mm. You say it is comparable to the equivalent Nagler, while I find it unacceptable. I suspect the reason may be my eyes are unable to compensate for the field curvature.

 

It's possible that the Nirvana has design changed since I had the 16mm UWAN (which was the version I owned for a while). Also it was now quite a few years ago.

I went from the 16mm UWAN to the 16mm Nagler T5 and could not see a lot of difference but that's just my take.

I don't wear glasses when observing and back then did not use them at all for anything. I use them for reading now.

I think the best we can do is to caveat each report / opinion with "Your Mileage May Vary, and Probably Will" and leave it at that !

 

 

[michael.h.f.wilkinson]

1 hour ago, Ags said:

Here is a direct and recent shootout between a another TMB Planetary clone and an SLV at F4.9:

Looks like a draw or near draw (considering only on-axis performance) according to the OP and some replies in the thread. Gives me pause for thought.

That report was done at 375x, so seeing probably limited performance. I have the 4mm SW Planetary as part of a set of EPs for my kids' mini-Dobson. I have used it in my 80 mm F/6 triplet, where it performed nicely, but I prefer the views through the 5mm SLV (different magnification however). 

[Geoff Barnes]

Thanks for dragging that old post of mine up @Ags, that was almost one year ago exactly and brought back fond memories of a great evenings viewing. I'm hoping to repeat that comparison when Jupiter and Saturn come into view above the trees in about another month or so. I will also give my new SLV 2.5mm a shot at Saturn just for fun, 600x mag through my 12 inch Dob should be revealing if conditions allow!  

[Stu]

44 minutes ago, Ags said:

@John I am thinking of our contrary feelings about the Nirvana 16mm. You say it is comparable to the equivalent Nagler, while I find it unacceptable. I suspect the reason may be my eyes are unable to compensate for the field curvature.

 

Would a lot not also depend on the scope it was being used in, and whether the eyepiece was amplifying or cancelling out the field curvature of the scope? Longer focal length newt very different from a shorter focal length frac in that regard.

I think you always have to consider the scope alongside the eyepiece; I often see comments like ‘the XXmm eyepiece in the range is the best’ but surely that depends what focal length and type of scope it is used in?

[John]

59 minutes ago, Stu said:

Would a lot not also depend on the scope it was being used in, and whether the eyepiece was amplifying or cancelling out the field curvature of the scope? Longer focal length newt very different from a shorter focal length frac in that regard.

I think you always have to consider the scope alongside the eyepiece; I often see comments like ‘the XXmm eyepiece in the range is the best’ but surely that depends what focal length and type of scope it is used in?

Very true Stu.

The eyepiece is actually quite low down on the "wobbly stack" of factors that affect what we actually see.

 

[Ags]

1 hour ago, Stu said:

Would a lot not also depend on the scope it was being used in, and whether the eyepiece was amplifying or cancelling out the field curvature of the scope? Longer focal length newt very different from a shorter focal length frac in that regard.

I think you always have to consider the scope alongside the eyepiece; I often see comments like ‘the XXmm eyepiece in the range is the best’ but surely that depends what focal length and type of scope it is used in?

Oh, I have tried! The Nirvana 16 has been in an ST80, Skymax 102, C6 at F10 and C6 at F6.3 (with flat field). It behaves consistently in all of them.

...And then on some nights it gives phenomenal views of the moon. Can eyepieces be subject to tidal forces?

Edited July 2, 2020 by Ags

[Louis D]

28 minutes ago, Ags said:

Oh, I have tried! The Nirvana 16 has been in an ST80, Skymax 102, C6 at F10 and C6 at F6.3 (with flat field). It behaves consistently in all of them.

...And then on some nights it gives phenomenal views of the moon. Can eyepieces be subject to tidal forces?

As far as affordable UWAs, has any done a head to head between the Nirvana 16mm and the Luminos 15mm?  The latter is considered one of the best of that line.  I doubt I could use either with eyeglasses, so I'm out for comparing them.  I'd be reporting all sorts of astigmatism across the entire field without eyeglasses.

[Don Pensack]

6 hours ago, John said:

I've seen measured data on the light transmission of various eyepieces and there is some variation (as you might expect) between the designs which might also contribute to the perception of one being dimmer / darker than another. Of course a dark background sky is desirable but not dimming of the intended targets, especially faint ones !

The range was between 88% and 98% of visible wavelengths. 

 

 

 

Note that a 10% difference is about 0.1 magnitude, i.e. if a magnitude 16.1 star can be seen in the highest transmission, it will only reduce to a magnitude 16.0 star in the lowest transmission.

To all intents and purposes, all those eyepieces had the same transmission because hour to hour variations in the sky alone exceed 0.2 magnitudes.

Yet, some eyepieces appear darker than others.   I think Michael's explanation carries some weight.  Also differences in light scatter (this may be a big one), chromatic aberration, etc.

[Ricochet]

8 hours ago, Ags said:

I know I am in the minority. It's either my eyes or my eyepiece. I should have sent the Nirvana 16 back at the time, but I really wanted to like it.

A thread I think well worth reading is http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483 which attempts to give measurements for the aberration size for quite a large selection of eyepieces. The 16mm Nirvana is listed under United Optics UWA(N) and the author agrees with you, the 16mm is poorly corrected. 

6 hours ago, Louis D said:

As far as affordable UWAs, has any done a head to head between the Nirvana 16mm and the Luminos 15mm?  The latter is considered one of the best of that line.  I doubt I could use either with eyeglasses, so I'm out for comparing them.  I'd be reporting all sorts of astigmatism across the entire field without eyeglasses.

According to the above website the Luminos is a touch better at f4 but about even at f10. 

[Ags]

@Ricochet that's a great link - and it looks like the NLV eyepieces score really well and I guess SLVs would be similar. I can't see TMB clones in the list unfortunately.

[Louis D]

37 minutes ago, Ricochet said:

A thread I think well worth reading is http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483 which attempts to give measurements for the aberration size for quite a large selection of eyepieces. The 16mm Nirvana is listed under United Optics UWA(N) and the author agrees with you, the 16mm is poorly corrected. 

According to the above website the Luminos is a touch better at f4 but about even at f10. 

It definitely matters at what f-ratio you test them.  The NT5 16mm is pretty much immune to fast focal ratios compared to the UO and Celestron equivalents.  At f/10, there's much less to separate them, though.

[John]

1 hour ago, Ricochet said:

A thread I think well worth reading is http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483 which attempts to give measurements for the aberration size for quite a large selection of eyepieces. The 16mm Nirvana is listed under United Optics UWA(N) and the author agrees with you, the 16mm is poorly corrected. 

According to the above website the Luminos is a touch better at f4 but about even at f10. 

That is a very interesting link

I can't honestly recall what scope I used the 16mm UWAN in

I have read elsewhere that it is considered the weakest of that 82 degree range but I didn't think of it as poor and it did compare well to the 16mm T5 Nagler that I replaced it with. I would have compared the two in the same scope during the short time that I owned them both.

At the time I did kind of regret the additional funds that I had spent acquiring the 16mm Nagler.

I have also used and owned the 28mm Nirvana and the 4mm and thought those very good eyepieces, perhaps a touch better than the 16mm ?

Sorry that you did not get on with this eyepiece @Ags and sincere apologies if my reports on it misled you in anyway

Perhaps Ernest will be a better guide than me for your future purchases ?

[Ags]

No need to apologise @John, people can only give their honest opinion as you did. I read lots of opinions and went with the consensus. And on some nights the eyepiece does deliver great views - lovely views of the moon at 94x for example. It's a bit of a mystery really. It seems when I am looking AT something the eyepiece is great, but when I am looking FOR something I find it frustrating. I bought the eyepiece for finding rather than for looking, hence my overall assessment. I think in finder role my attention is off axis, and the Russian link does indicate the Nirvana struggles away from the center of the field.

What I keep coming back to is that the Explore Scientifc 24/68 performs perfectly in all my scopes including the ST80 despite having a far larger field stop. I wanted the Nirvana to replace it as a finder as the ES is optically perfect but the exit pupil was too large for my location. I know the ES 24/68 is really very, very good and many eyepieces would suffer in comparison.

Once again, don't apologise - I always find your contributions informative and entertaining! It's a big responsibility putting one's thoughts online about an eyepiece or other item, but the community depends on people sharing their experiences - or we would only have the word of retailers and manufacturers.

I am not anti the Nirvana series as a whole, I am toying with getting the 4mm as the shortest focal length in my collection - at that magnification 82 degrees field might be more practical than 45 degrees.

Edited July 2, 2020 by Ags

[Ricochet]

1 hour ago, Louis D said:

It definitely matters at what f-ratio you test them.  The NT5 16mm is pretty much immune to fast focal ratios compared to the UO and Celestron equivalents.  At f/10, there's much less to separate them, though.

Indeed, and it is that performance at fast ratios that you are paying for with TV eyepieces, as well as the often forgotten quality of coatings, which I imagine perform better across all focal ratios, even as the difference in correction decreases.

1 hour ago, John said:

That is a very interesting link

Yes, I find myself referring to it surprisingly often.

1 hour ago, John said:

I have also used and owned the 28mm Nirvana and the 4mm and thought those very good eyepieces, perhaps a touch better than the 16mm ?

I believe that is the general consensus. I've got a 28mm Nirvana, and it is a very good eyepiece, but I do see issues as I look to the edge that tie in quite well with the assessment given, albeit without any measurements on my part. Astigmatism, I agree with, CA, I can't say I recall, but then I'm only using it in a Newtonian so there is no additional CA from the scope, and also I think a bit of FC. However, this is really being quite picky and it is only through time and practice that my eyes and brain have become "sharper" and I have become able to judge, or even notice such details. If noticing such details becomes too distracting then things can get expensive quite quickly. Sometimes it is better to think back to earlier times when such things were not noticed and remember to just enjoy the views.

 

[Ags]

22 hours ago, John said:

The eyepiece is actually quite low down on the "wobbly stack" of factors that affect what we actually see.

Not sure I agree, especially after my collection of Hyperions encountered my shiny new F5 Newt a few years ago.

[jetstream]

On 02/07/2020 at 07:49, John said:

Very true Stu.

The eyepiece is actually quite low down on the "wobbly stack" of factors that affect what we actually see.

 

Totally agree.

Unless there is a poor reaction between the scope and the eyepiece ie my Zeiss zoom and f3.8 newt, the eyepiece is the last thing on the list IMHO. For info: the PCII straightens this EP out at f4.1.

 

[Ags]

Well, I found a new home for my Nirvana 16 - or, more accurately, a new home found my eyepiece. So I am pivoting away from thinking about SLVs to plugging my new gap in the 16mm mark. So I have started the hunt for the 16mm and 20mm Explore Scientific 68 degree eyepieces.