A Review of the Svbony 3-8mm

[Mr Spock]

My review of this eyepiece was conducted over several nights using a StellaLyra 12” Dobsonian, and a Takahashi FC-100. Each focal length was compared to a number of eyepieces of similar focal length on both double stars and the moon. Seeing on each night was very good to excellent. As usual for my location transparency was poor due to light pollution.

This eyepiece rates very highly with a lot of observers. At the current price (I paid £81 for mine) it is extremely good value for money. It is interesting to compare this zoom with fixed focal length eyepieces costing many times more each.
The eyepiece itself appears well built with an excellent build quality for the price. It has an undercut on the barrel which isn’t too severe and shouldn’t cause problems with twist grips. In action the zoom movement is quite stiff. The top part of the eyepiece remains in the same position but moves outwards when zooming in. The zoom twist grip itself has a knurled appearance and is quite easy to grip. Due to the stiff action I tend to hold the top part of the eyepiece while twisting the zoom grip. 
Although nominally a zoom which goes from 8mm to 3mm in 1mm click stops, it does measure quite differently. The stops are actually at 8.1mm, 7mm, 6mm, 5.2mm, 4.4mm, 3.5mm. The field of view is close to 58° throughout the range. Eye relief can get quite tight towards 3mm, and I had to observe with the eyecup folded down. Not an eyepiece I’d recommend for those who need to wear glasses.

Double Stars

This was mainly conducted with the FC-100 as despite the decent seeing the 12” wasn’t really showing clean airy disks in any eyepiece. At all settings the eyepiece presented clean looking airy disks in the FC-100. There wasn’t really any noticeable difference between this eyepiece and any of my others. The eyepiece was close to par focal at all focal length with just minor tweaks needed towards the short end. Highly recommended for double stars. For the FC-100 that would mean for me just three eyepieces: the 42mm LVW for a finder, the 17mm LVW for a wide view, then the 8-3 for splitting. Perfect!

The Moon

I’ll concentrate on the 12” first as this is where a few problems started to appear.
8mm: the centre of the image was sharp but not quite up to the 8mm LVW but very similar to the 7mm (which measures 8mm) Nirvana. Unlike the Svbony, however, the 7mm Nirvana was sharp to the edge; the Svbony showing very marked field curvature. You could re-focus the edge, so that confirms it is field curvature. Very poor.
7mm: Compared to the 7mm Circle-T Orthoscopic the view was very similar. The 43° view of the ortho matched the in-focus area of the Svbony. The ortho lost out due to light scatter from its non-existent coatings. The Svbony seemed quite well controlled in this respect throughout its range. Again, very poor field curvature.
6mm: Compared to the 6mm SLV it was again close with the SLV just a touch sharper. It’s not something you would notice unless viewing side by side. Compared to the 6mm Circle-T orthoscopic it was very similar in most ways.
5mm: Compared to the 5mm LVW the LVW had a more relaxed view though I’ve found with the 12” this eyepiece needs accurate eye positioning. The Svbony felt quite comfortable as far as eye relief was concerned and overall, the performance was quite similar.
4mm: Compared to the 4mm Nirvana, 4mm Circle-T Orthoscopic and 4mm TOE. This was no contest with the TOE showing much finer detail than the others. At over £300 each I’d have been a bit disappointed if the TOE had failed here! The Svbony’s field curvature wasn’t so pronounced at this focal length and just about acceptable. The 4mm Nirvana, as with the 7mm, was sharp to the edge. For eye relief the 4mm Ortho was actually easier to look through than the Svbony, though this ortho has more ‘haze’ from scatter than the other eyepieces used.
3mm: or more correctly, 3.5mm. Compared here to the 3.5mm LVW and 3.3mm TOE. Eye relief in the Svbony was so tight I rolled the eyecup down. As before central definition of the Svbony was excellent and just a touch behind the TOE and LVW. As with the 5mm, the 3.5mm LVW suffers critical eye positioning and blackouts are frequent and annoying.

Using the same set of eyepieces, the FC-100 is up next.
8mm: The field curvature seen in the 12” was not evident here. There was just a bit of falling away on the outer edge. Definition was quite pleasing with good contrast and detail. The 8mm LVW was just a touch crisper and the 7mm Nirvana similar. 
7mm: The Svbony was preferred to the ortho due to the lack of scatter. The orthos are much better on planets like Jupiter where there isn’t that extreme brightness.
6mm. Very little field curvature and a very similar performance to the 6mm SLV.
5mm. No blackouts from the LVW at this focal length so it won this contest. The margin was very small though with the Svbony exhibiting excellent sharpness.
4mm: No surprise the TOE was ahead here. In particular the way it showed Gassendi N and the rille next to it. It was just so much cleaner and crisper than the Svbony or the Nirvana.
3mm: Same result as above v the TOE. However, without the blackout issues of the 12”, the 3.5mm LVW moved ahead here. The view was just so much more relaxed than either of the other two. Especially compared to the tight eye relief of the Svbony. I spent the rest of the night (several hours) enjoying the moon though the 3.5mm LVW. Going back to Gassendi N, it was very sharp with a finely etched rille close by, in both the TOE and LVW; the Svbony was just a little less distinct, but certainly not a lot in it.

Verdict.
What’s not to like about an eyepiece with this level of almost high-end performance across a decent range of 8.1mm to 3.5mm and at just £81. My recommendation? At this price v performance everyone (except glasses wearers) should have one. Just be wary of potential field curvature in some scopes. Overall, though, it really is the bargain of the century!

[Roy Challen]

An interesting read, thanks Michael. Definitely agree with it being an absolute bargain. Is there any other eyepiece that does so much, for so little? Probably not.

[GordonD]

A great, detailed report - thanks for posting it.

[Ratlet]

Great review.  Do you think you'll add to it when the planets get back on display? 

[Mark at Beaufort]

An excellent review Michael. I have had the SvBony zoom for about 5 months and have found it very useful on my StellaMira125mm frac.

[MarkOw]

Great review - I have one of the 7.6-21.8mm Svbony zoom eyepieces which works really well with an 8" SCT, but just ocasionally I want another magnification level, so might add one of these to my wishlist for plantery viewing in good seeing conditions.

Thanks for taking the time to write it up so comprehensively.

Edited April 22 by MarkOw

[Mr Spock]

1 hour ago, Ratlet said:

Do you think you'll add to it when the planets get back on display? 

Yes. It will be nice to do a comparison on Jupiter especially. Some of the fine detail in the belts is a good test for any eyepiece.

[DirkSteele]

Nice review.  Seems like a bargain eyepiece, even noting some of the short comings you highlighted.  

 

On that, Sidgwick gives the formula 4 x (1.22 x wavelength x Focal Ratio²) to calculate depth of focus.  As it is proportional to focal ratio squared, the f/7.4 Tak would have 2.2x the depth of focus compared to the f/5 Dobsonian.  I wonder if that might be a contributor to your perception of poor field curvature in the 12-inch?  Intrinsically, the Dob with its 1,520mm focal length should show less curved field than the 740mm focal length Tak (though the relationship between field curvature and focal length is not quite as straight forward as with a Newtonian, but it still primarily focal length).  Perhaps the focal ratio is also stressing the zoom.  Virtually all eyepieces look good at f/10, but f/4-5 tends to sort the run of the mill from the superstars.

 

 

[Naughty Neal]

Great review Michael and certainly yes ,100% a bargain of the century.  To put it mildly if one makes use of the 0.5mm settings between the main stops one is getting a  very good multi FL EP which accrues to approx £8 for each  FL of 0.5mm (if bought at the bargain price of £80).  

Purists will still want their fixed FL favourite EP's but for travelling and weight an all in one EP,  for those on a budget a must have EP which with a  pair of quality EPs in the 15 - 30mm range will be all that  is required.

Edited April 24 by Naughty Neal

[russ]

Great review. It is one of the best value eyepieces on sale. I wouldn't swap mine for anything. I've sold all my high power eyepieces.

[LukeTheNuke]

Thanks for taking the time to do a review. This one tempts me. I've thought about the Tele Vue 3-6 mm zoom a few times, but what puts me off is the cost combined with knowing my wife Sarah wouldn't like it (I think the eye relief would be too tight for her). I could justify the cost of this one from Svbony. And a 3 to 8 mm range sounds very useful. I don't think I've tried anything from Svbony yet, but I get the impression that some of their stuff may be good bang for buck from what others are saying. I have pondered trying a few of their cheap cameras, maybe for some lunar imaging.

[Ags]

Svbony’s sales blurb makes a point about the eyepiece being well suited for “premium refractors” so that makes me think the curvature is matched for those grab and go apos and not a big newt. I can’t say I’ve seen curvature in my 66 or 90 mm refractors. I love this eyepiece, it gives everything from one degree FOV to max magnification in the fracs, so I don’t need any other eyepieces!

[Mr Spock]

I very quickly gave up on using it for double stars. The change in focus is too much of a jump from my other eyepieces and I just got annoyed with it. My old set up of 42mm LVW as finder, then 16mm, 7mm(8mm), 4mm Nirvanas works perfectly for doubles so I've been using that tonight.
As I have better planetary eyepieces at 8mm, 6mm, 4mm, 3.5mm, I shall probably end up selling it as it isn't going to get any use.

[John]

15 minutes ago, Mr Spock said:

I very quickly gave up on using it for double stars. The change in focus is too much of a jump from my other eyepieces and I just got annoyed with it. My old set up of 42mm LVW as finder, then 16mm, 7mm(8mm), 4mm Nirvanas works perfectly for doubles so I've been using that tonight.
As I have better planetary eyepieces at 8mm, 6mm, 4mm, 3.5mm, I shall probably end up selling it as it isn't going to get any use.

I found mine excellent again tonight. Very nearly par-focal from 8mm to 5mm I felt with a small adjustment moving to 4 and 3mm (3.5mm really). The Nagler 2-4mm is almost perfectly par-focal across it's range but the Svbony is not far off, IMHO.

That was in an F/7.5 120mm refractor. 

Still, it's not going to suit everybody, granted.

I did like the 4mm Nirvana when I had one a while back.  

 

Edited Sunday at 23:32 by John

[Mr Spock]

When I use the Nirvanas, they are all nearly par focal. So I leave it at that focus and slip the 42mm in part way until it's focused. Whether I use the 16mm Nirvana or the 17mm LVW as an intermediate, going to the 8mm of the Svbony is a huge amount of in-focus. Given the brightness of stars I'm looking at I can't even see if they are there they are so out of focus.

[John]

22 minutes ago, Mr Spock said:

When I use the Nirvanas, they are all nearly par focal. So I leave it at that focus and slip the 42mm in part way until it's focused. Whether I use the 16mm Nirvana or the 17mm LVW as an intermediate, going to the 8mm of the Svbony is a huge amount of in-focus. Given the brightness of stars I'm looking at I can't even see if they are there they are so out of focus.

There is a considerable amount of difference in the focal plane position with eyepieces of different designs and brands. I usually use a Pentax XW before stepping down to the Svbony 3-8 zoom and there is some further inwards focuser movement needed - maybe 4mm or so ?

If I need to step down further than the Svbony 3-8 goes I generally go to the Nagler zoom 2-4mm which needs around 10-12mm outwards focus movement. 

I find that slightly annoying, but, having always had a wide range of eyepieces in my case, I'm kind of used to it 🙂

Maybe I should move to TV Delos's from the Pentax XW's and then I could have a set that is totally par focal from 24mm (Panoptic) to 2mm (Nagler zoom) 🤔

Hint: don't try an APM super zoom in 1.25 inch mode - that really will annoy you 😉