Eyepiece comparison

[Franklin]

Brrr.... Bitterly cold last night, out around midnight for only an hour. Still experimenting with the Svbony 3-8 zoom and the target was of course the Moon. I thought I'd try something a little more scientific😁, yeah right! and finally found a use for my Vixen flip-mirror diagonal, with the tripod extended higher than usual I was able to make instant comparisons between eyepieces by flipping between diagonal and straight through viewing. I alternated the positions as the straight through view holds an unfair advantage. I compared the 3-8 zoom on the 6mm, 4mm and 1/2 way between 3 and 4mm settings with my SLV 6mm, SLV 4mm and the HR 3.4mm eyepieces. Magnification used was 104x, 156x and 183x, all in the SD81S. The seeing was quite still last night and there was none of that high, hazy cloud around either, the conditions were good, apart from the cold. Firstly, the fov in the zoom is a bit wider than the SLV's and considerably more than the HR with it's "orthoscopic" sized 42deg. The view of the Luna terminator was etched, crisp dark shadows offering excellent relief, revealing features with high contrast, the SLV 6mm and zoom @6mm performed equally, I could see no difference. Upping the power with the SLV 4mm and the zoom @4mm, to my eye I could not see a noticeable difference between the image presented. This 156x power is taking the SD81S to around it's limits really with an exit pupil of 0.5mm and I could see a hint of CA appearing off-axis in the shadows of Luna craters but this was not noticeable in the straight through view, alternating SLV with zoom confirmed that this hint of CA must be coming from scatter from the mirror diagonal. Still, the views through both were very good and without noticeable difference. Finally I set the zoom about half-way between 3mm and 4mm and compared that to the HR3.4 giving a magnification of 183x and an exit pupil of 0.44mm. This is the point where things became interesting because although the Svbony held up very well and presented an image that was still useable, despite the slight over-power, the zoom image definitely had become softer. Whereas the HR3.4 presented an image that remained crisp and with the same high contrast that the others at lower power revealed. I think that if I'd been using my larger refractor this difference would have been less noticeable and that's something I will have to try at a later date but from doing this I've seen for myself that a "budget", "made in China" zoom can perform on a pretty much equal standing with more expensive "made in Japan" eyepieces. The better performance of the HR is obviously due to its more sophisticated design regards control and suppression of stray light, it's just a shame they can't design an eyepiece that suppresses floaters in the observers eye! An enjoyable hour despite the cold and the only conclusion I can draw is that the view through all eyepieces was very good indeed but the Svbony zoom cost £75 new and the three Vixen eyepieces set me back £400 used.

edit. just realised I've posted this in the "What did you see last night" thread and it's more of an eyepiece test post however, last night I saw the Moon😁.

Edited December 1, 2023 by Franklin

[Stu]

Split out into its own thread and put into the eyepiece discussion forum 👍

[Stu]

Interesting comparison Tim. I think the Chinese gear often performs very well, and it’s only in the more extreme tests under excellent conditions that you can see the differences with more expensive kit.

[Franklin]

42 minutes ago, Stu said:

I think the Chinese gear often performs very well

Also Vixen moved production of there SLV's to China so that tells a story of improved manufacturing over there.

[cajen2]

I've got the Svbony zoom on order. I'll be fascinated to see how it compares to my Morpheus 4.5 and 6.5mm. It'll give me a chance to go higher than 159x mag in my Starfield 102ED, for the moon, Saturn and double stars.

[Franklin]

2 minutes ago, cajen2 said:

I'll be fascinated to see how it compares to my Morpheus 4.5 and 6.5mm

Apart from the smaller fov I think you will be impressed.

[Stu]

47 minutes ago, Franklin said:

Also Vixen moved production of there SLV's to China so that tells a story of improved manufacturing over there.

I think they are absolutely capable of producing top notch kit, it’s just most of the time their customer push for low cost prices which prevents them from doing it. Given a spec and reasonable cost price target, the quality can be there.

[johnturley]

3 hours ago, Franklin said:

Brrr.... Bitterly cold last night, out around midnight for only an hour. Still experimenting with the Svbony 3-8 zoom and the target was of course the Moon. I thought I'd try something a little more scientific😁, yeah right! and finally found a use for my Vixen flip-mirror diagonal, with the tripod extended higher than usual I was able to make instant comparisons between eyepieces by flipping between diagonal and straight through viewing. I alternated the positions as the straight through view holds an unfair advantage. I compared the 3-8 zoom on the 6mm, 4mm and 1/2 way between 3 and 4mm settings with my SLV 6mm, SLV 4mm and the HR 3.4mm eyepieces. Magnification used was 104x, 156x and 183x, all in the SD81S. The seeing was quite still last night and there was none of that high, hazy cloud around either, the conditions were good, apart from the cold. Firstly, the fov in the zoom is a bit wider than the SLV's and considerably more than the HR with it's "orthoscopic" sized 42deg. The view of the Luna terminator was etched, crisp dark shadows offering excellent relief, revealing features with high contrast, the SLV 6mm and zoom @6mm performed equally, I could see no difference. Upping the power with the SLV 4mm and the zoom @4mm, to my eye I could not see a noticeable difference between the image presented. This 156x power is taking the SD81S to around it's limits really with an exit pupil of 0.5mm and I could see a hint of CA appearing off-axis in the shadows of Luna craters but this was not noticeable in the straight through view, alternating SLV with zoom confirmed that this hint of CA must be coming from scatter from the mirror diagonal. Still, the views through both were very good and without noticeable difference. Finally I set the zoom about half-way between 3mm and 4mm and compared that to the HR3.4 giving a magnification of 183x and an exit pupil of 0.44mm. This is the point where things became interesting because although the Svbony held up very well and presented an image that was still useable, despite the slight over-power, the zoom image definitely had become softer. Whereas the HR3.4 presented an image that remained crisp and with the same high contrast that the others at lower power revealed. I think that if I'd been using my larger refractor this difference would have been less noticeable and that's something I will have to try at a later date but from doing this I've seen for myself that a "budget", "made in China" zoom can perform on a pretty much equal standing with more expensive "made in Japan" eyepieces. The better performance of the HR is obviously due to its more sophisticated design regards control and suppression of stray light, it's just a shame they can't design an eyepiece that suppresses floaters in the observers eye! An enjoyable hour despite the cold and the only conclusion I can draw is that the view through all eyepieces was very good indeed but the Svbony zoom cost £75 new and the three Vixen eyepieces set me back £400 used.

edit. just realised I've posted this in the "What did you see last night" thread and it's more of an eyepiece test post however, last night I saw the Moon😁.

I did a comparison a few years ago between a 4mm Vixen SLV and a 3-6mm Nagler Zoom at 4mm on the moon, there wasn't much difference between the sharpness and contrast of the two eyepieces, but I preferred the significantly wider field of the Nagler Zoom, although in theory they have the same APFOV. I subsequently decided to sell the SLV, partly because there wasn't enough room in my main eyepiece case for both.

John 

Edited December 1, 2023 by johnturley

[bosun21]

1 hour ago, cajen2 said:

It'll give me a chance to go higher than 159x mag in my Starfield 102ED

Just barlow the 6mm. Works great, and if you use a telextender there’s no change in ER.

[cajen2]

Ah, but the zoom gives more flexibility - out to 8mm to centre the target, then in to get close ups. Just another string to my bow. I have a couple of decent Barlows: an ES 2x focal extender and the 2.25x one for the Baader zoom, but I prefer not to use them if I don't have to.

[Louis D]

3 hours ago, Franklin said:

Firstly, the fov in the zoom is a bit wider than the SLV's and considerably more than the HR with it's "orthoscopic" sized 42deg.

There shouldn't be much apparent field of view difference between the SLVs and the HR.  The LVs, NLVs, and SLVs below 9mm all have 45 degree apparent fields despite what the later versions claimed.  Check it for yourself.  Hold up a ~50 degree plossl to one eye and either the 4mm or 6mm SLV to the other eye while looking at a bright background.  The SLVs will have a smaller image circle.  The Svbony zoom has an AFOV between 58 and 61 degrees, so it should look considerably wider than either the SLVs or HR.

[Louis D]

4 hours ago, Franklin said:

Upping the power with the SLV 4mm and the zoom @4mm, to my eye I could not see a noticeable difference between the image presented.

I noticed the 4mm setting getting slightly softer, but still quite usable.  From 5mm to 8mm, I'd rate the Svbony zoom as excellent.

[Franklin]

1 minute ago, Louis D said:

There shouldn't be much apparent field of view difference between the SLVs and the HR. 

Yes I know the numbers but I see a bigger apparent difference between the SLV and HR than the Zoom and SLV. The SLV's shorter than 9mm are definitely less than 50deg as you say. Maybe my zoom is not quite as advertised?

[Louis D]

4 hours ago, Franklin said:

Finally I set the zoom about half-way between 3mm and 4mm and compared that to the HR3.4 giving a magnification of 183x and an exit pupil of 0.44mm. This is the point where things became interesting because although the Svbony held up very well and presented an image that was still useable, despite the slight over-power, the zoom image definitely had become softer.

You need not have bothered with the in between setting.  I measured the 3mm setting to actually be 3.5mm in the central region.  It grows to 2.5mm at the edges due to distortion.  And I also noticed considerable softening at the "3mm" setting.  I consider it a bonus focal length to be used when you don't have anything better.

Edited December 1, 2023 by Louis D

[Louis D]

3 minutes ago, Franklin said:

Yes I know the numbers but I see a bigger apparent difference between the SLV and HR than the Zoom and SLV. The SLV's shorter than 9mm are definitely less than 50deg as you say. Maybe my zoom is not quite as advertised?

Do the same test holding one up to each eye, but with zoom and the SLV.  It could be that if you are concentrating on the central region against a dark sky, you aren't noticing the wider FOV.  It could also be the tighter eye relief coming into play.  You really need to mash your eye into the zoom's eye cup to take in the entire FOV, especially from 3mm to 6mm.

[Franklin]

14 minutes ago, Louis D said:

The Svbony zoom has an AFOV between 58 and 61 degrees, so it should look considerably wider than either the SLVs or HR.

You're correct, as usual😁, I've just had the SLV6 and the Svbony zoom @6 both next to each other in either eye against a bright sky background and yes the zoom is noticeably wider, strange how at night this wasn't noticed as much. In fact the difference between the zoom and SLV is greater than the difference between the SLV and HR as the figures suggest. It could be eye relief as you say but the HR is quite claustrophobic as good as it is.

Edited December 1, 2023 by Franklin

[John]

Good write up @Franklin 👍

I used the Svbony 3-8 zoom with my TMB/LZOS 130 F/9.2 last night. I did compare it casually with the Nagler 2-4 zoom and the 3.5mm Pentax XW but didn't notice any significant differences, apart from the AFoV.

With the somewhat variable and cold conditions for observing last night detailed comparisons, when using magnifications of 300x plus, were a little futile I felt. Perceived differences could be just as much caused by variations in seeing, local heat emissions, thin high clouds or even a watering observing eye (due to the cold).

I might also not be such a fussy observer these days, having not been able to notice any difference between a Tak TOE 4mm and the Nagler 2-4mm zoom on the occasions when I compared them back in the summer, despite a number of other folks assuring me that there is a noticeable difference 😉

 

Edited December 1, 2023 by John

[Louis D]

1 hour ago, John said:

I did compare it casually with the Nagler 2-4 zoom and the 3.5mm Pentax XW but didn't notice any significant differences, apart from the AFoV.

I had to go back to my Svbony zoom write up to remind me of what I saw in the 3.5mm Pentax XW versus the Svbony zoom at 3mm:

So, I'd recommend looking for color fringing on bright stars as you move them center to edge.  The XW shows none anywhere while the Svbony zoom shows increasing amounts toward the edge.

[Ratlet]

Great write up.  I've been perpetually delighted with my 3-8mm since it turned up last year.  In my opinion, if you don't wear glasses it makes an excellent upgrade eyepiece choice for a starter set for planetary.  

[John]

20 minutes ago, Louis D said:

I had to go back to my Svbony zoom write up to remind me of what I saw in the 3.5mm Pentax XW versus the Svbony zoom at 3mm:

So, I'd recommend looking for color fringing on bright stars as you move them center to edge.  The XW shows none anywhere while the Svbony zoom shows increasing amounts toward the edge.

I have not noticed colour fringing with the Svbony 3-8 zoom, even at the shorter settings. I have let Saturn drift right across the field of view a few times at the 4mm and 3mm settings and the image remained sharp and well defined even as it slipped behind the field stop edge. Similarly with the tight double star Pi Aquarius. 

My scopes are not that fast though - F/6.5 - F/9.2.

I don't tend to spend time looking for faults in optics these days though. If something pops out I notice it but while the image remains good, I'm good with the eyepiece 👍

I will be interested to see how the Svbony 3-8 does on Sirius and the Pup star later this year though 🙂

 

Edited December 1, 2023 by John

[John]

Posted in error.

Edited December 1, 2023 by John

[bosun21]

7 hours ago, cajen2 said:

Ah, but the zoom gives more flexibility - out to 8mm to centre the target, then in to get close ups. Just another string to my bow. I have a couple of decent Barlows: an ES 2x focal extender and the 2.25x one for the Baader zoom, but I prefer not to use them if I don't have to.

I used to own the Svbony 3-8mm zoom but sold it. I couldn't get on with the short eye relief and relatively small eye lens. I think I've just grown too accustomed to the long eye relief and huge eye lens of the Morpheus eyepieces. All this talk has me eyeing another one. I'll give it a concerted effort this time.

[John]

The more I use it and hear what others think of it, the more I think that the Svbony 3-8 zoom sits pretty much in the niche that the Nagler zooms occupy. Not the absolute top tier planetary eyepiece performance but close enough to it, and coupled with the zoom facility plus reasonable AFoV and eye relief for the non-glasses wearer, that it becomes a very useful addition to the eyepiece case. The big bonus is that the Svbony costs around 25% of the cost of a Nagler 3-6 zoom so will find a place in a lot more eyepiece collections 🙂

 

 

[Ags]

The Svbony 3-8 lives in the focuser of my small refractors. At the wide end it gives a bit more than 1 mm exit pupil and a 1 degree of FOV, so perfect for 99% of DSOs, and the zoomed function takes care of doubles, the Moon and planets.

I also own a bunch of NLVs and SLVs and they win on comfort by a big margin. If I am taking a good long look at something, I would rather use my SLV 6 or NLV 9. I would say they give a better view too, cleaner and more contrasty. Despite that, the Svbony 3-8 is the one in the focuser.

[SuburbanMak]

I have written a letter to Santa about an SV Bony 3-8mm zoom, would give a very useful range of higher magnification in the F7.4 Tak 100 DC. Fingers crossed…