SVBONY 68° Ultra Wide Angle 20mm Eyepiece First Look

[Louis D]

Based on a recent comment by another SGL user that the SVBONY 68° Ultra Wide Angle 20mm eyepiece was sharp and gives very clear images in an f/6 Dob, I thought I'd get one to try out in my field flattened f/6 AT72ED refractor to see if somehow this repackaged $30 eyepiece is working some kind of miracle at that price point.

I measured it to have a 67° AFOV, a 68° effective AFOV (eAFOV) due to slight edge distortion, a 23.7mm field stop, 14mm of usable eye relief, a 24mm diameter eye lens, and 3.1 ounces (88g) in weight.  As such, it lives up to the ad for the most part.

Since it has been raining almost constantly here for the past 4 weeks, I haven't been able to get out and observe at all.  I think the night skies cleared up by early morning once during that time.  As a result, I'm constrained to indoor testing for now.

It's a bit shy on eye relief for me when wearing eye glasses.  I need about 2mm to 3mm more eye relief to see the entire field comfortably.  However, I would estimate I can see about 80% of the field while wearing eyeglasses.  It's easy enough to tip my head slightly to take in the edges.

The eye cup snaps up and down with relative ease, and yet it stays up when used without eyeglasses.  It's very similar to many budget Plossl eye cups.

The center appears to be sharp, but the edge sharpness falls off noticeably in the last 25% of the field.  Refocusing did not improve things, so it appears to have a flat field insofar as I can tell in an f/6 field flattened scope.  I'm guessing astigmatism is the primary cause of edge unsharpness since I didn't see any appreciable chromatic smearing.  It is not sharp edge to edge at f/6, but it is pretty sharp over the central 67% (45°) of the AFOV.  As such, it performs as well as a 20mm Plossl while providing more context.

Here's a couple of group beauty shots of the SVBONY alongside its more expensive competitors.  It certainly is a handsome looking eyepiece in gloss black, textured grip ring, engraved white lettering, and snazzy red anodized beauty rings.  It's much nicer looking than the earlier incarnations of this line of eyepieces such as the Orion Expanse and other 66° UWA variants.  It looks much more expensive than it's price tag would suggest.  It's also very compact for what it does.  It's fairly dense, though.  I was surprised by its heft in my hand.

Here's the updated 18mm to 22mm comparison image taken through the eyepiece of my standardized rulers target.  I've included the original eyepiece group shot for context.  I didn't feel like digging out all the other eyepieces to reshoot it.  Just imagine the new SVBONY slotted between the generic reversed Kellner and the Orion Centering SWA eyepieces.

As can be seen above, the SVBONY holds its sharpness farther off axis than the 20mm Orion Centering SWA, but it is not as wide in AFOV or TFOV.  It also has 3mm more usable eye relief which is quite noticeable.  I did not notice any SAEP kidney beaning in daytime usage.  The view is quite easy to acquire and hold.

It is head and shoulders better than the 20mm generic reversed Kellner in all respects except for physical size.

The SS zoom is incredibly sharp at 21.5mm, but also incredibly narrow in AFOV and short on eye relief (11mm).  Since the SVBONY can't zoom, it's not a relevant comparison.

It performs slightly better off axis than the 19mm GR Konig, but it is only marginally wider in AFOV.  I think the SVBONY is likely an improved Konig variant based on tear downs of the 20mm Expanse I've seen on CN.  There's a slight chance this version has been redesigned, but I'm not disassembling mine to find out.

Both the 18mm Meade HD-60 and AT Paradigm (BST Starguider) hold their sharpness better to the edge, but both have noticeably narrower AFOVs.  The HD-60 also wins out on usable eye relief at 19mm versus only 12mm for the Paradigm.

The 22mm AT AF70 holds its sharpness much farther off axis and is slightly wider in AFOV.  It also has more usable eye relief (16mm that feels more like 18mm in use).  It isn't much of a surprise it's better given how much bigger and more expensive it is.

And of course the 22mm Nagler T4 rules them all for sharpness and AFOV width, but at a significant size, weight, and price premium.  It's also a bit tight on usable eye relief at 14mm, although it feels like 16mm in use.

Once I get some time under the stars with it, I'll report back.  If I like it enough, I may get another for binoviewer usage.

[Louis D]

I had a quick look at the skies with the SVBONY 20mm through my field flattened AT72ED.

It is nicely sharp in the central 50% of the field of view, though I wouldn't say pin sharp just yet.  It then gets more astigmatic as you work your way to the edge.  It had about twice as much astigmatism at its 68 degree edge as did either the Paradigm (BST Starguider) or Meade HD60 18mm at their 60 degree edges.  The Paradigm and Meade seemed to be a bit sharper in the central portion of the field as well.

The field was close to flat.  Of course, with so much edge astigmatism, it's difficult to judge best focus there.

The extra 8 degrees of field in the SVBONY didn't seem all that noticeable.

Faint stars looked similar in all.  Bright stars seemed to wink out at the field stops well enough in all of them.

The SVBONY had vignetting before the edge.  Perhaps the last 5% of the field.  It was slight but noticeable.  I take it that the designers pushed the old 66 degree design another 2 degrees to 68 degrees by enlarging the field stop without altering the lens design.

It works surprisingly well with eyeglasses.  I didn't have any problems taking in the entire field while resting my glasses on the folded down eye cup.

There were no indications of SAEP (kidney beaning) that I could discern.

Next I'll have to try it in my 127 Mak at f/12.

Overall, it's surprisingly good for what I paid for it, but it is not sharp across the field at f/6.

[banjaxed]

Great review which appears to mostly agree with my amateur observations.

[John]

Sounds a similar performer to the William Optics SWAN 20mm but at a better price. Fine in slow refractors, maks, SCT's etc.

 

Edited June 12, 2021 by John

[Louis D]

2 hours ago, John said:

Sounds a similar performer to the William Optics SWAN 20mm but at a better price. Fine in slow refractors, maks, SCT's etc.

 

And quite similar looking when disassembled:

Two upper singlets and what appears to be a lower doublet, although the author claims it to be a triplet.

[Ricochet]

33 minutes ago, Louis D said:

And quite similar looking when disassembled:

Two upper singlets and what appears to be a lower doublet, although the author claims it to be a triplet.

The disassembled eyepiece is not a 5 element SWAN, but a 4 element WA. Trying to match the WA lenses to the specification for the SWAN is what has lead to the misidentification of the number of lenses in the lower group. 

Your assessment of the SVBONY is pretty much what I expected having used a 15mm gold line, which from memory was only usable in the central 1/3 at f6. 

[badhex]

Great review as always Louis, thanks. I have been wondering about the various SVBONY EPs flying about. 

[Louis D]

2 hours ago, Ricochet said:

The disassembled eyepiece is not a 5 element SWAN, but a 4 element WA. Trying to match the WA lenses to the specification for the SWAN is what has lead to the misidentification of the number of lenses in the lower group. 

That makes sense.  Very similar looking externally, but different internally:

I did have to laugh at WO's ad line for the 20mm SWAN: The ultimate 1.25” SWA eyepiece.  From the context within the ad, it probably should have said The ultimate compromise 1.25" SWA eyepiece.  However, that wouldn't have sounded so grandiose.

[Louis D]

I finally got around to trying out the SVBONY 68° UWA 20mm eyepiece in my 127 Mak.  As expected, it cleans up nicely to the edge.  I also snapped a picture through the Orion Centering SWA 20mm which is wider with poorer correction for comparison.  The SVBONY is a bit cleaner to the edge, but not by a huge margin.  If you have a slow scope, the SVBONY 68° UWA 20mm will probably work quite well in it.

[Carbon Brush]

Thank you Louis for the detailed review.

The saying about a picture saying a thousand words rings true here.
The distorted and blurry wooden rule describing comparitive FOV and edge sharpness are far better than a page of writing.
Also the 'seeing' is under your control allowing true comparison.

[0rcrest]

very helpful i'm looking to  upgrade  ep's for my heritage 130p f5  ,between my svbony  15mm 68 degree w/a and skywatcher  25mm ler ep. something in the middle 18mm bst ,vixen npl,swan etc 

[Louis D]

I bought a second SVBONY 68° Ultra Wide Angle 20mm when they went on sale for $20 shipped via ebay.  I finally had the chance to try them out as a pair in my Arcturus binoviewer with a Meade 140 2x Barlow nosepiece to reach focus.  In my f/6 Dob without CC, the 3x equivalent equates to about an f/18 operating focal ratio.

They work insanely well together.  Merging and holding the two images was a piece of cake.  There were no blackouts that had to be fought off.  Eye relief was sufficient to comfortably take in the view with eyeglasses while just touching the flipped down eye cups.  Stray light was well controlled as was scatter around the planets.  The sky background was nice and dark.  Sharpness was excellent to the edge (remember, f/18).  The pair was easily as good or better than my vintage wide field microscope eyepieces that had been my mainstays.  The 23.7mm field stop plays very nicely with the 22/23mm clear aperture of the binos.  I saw no vignetting near the sharp field stop.  The only downside was their barrel undercut.  I had to spin the collets quite a few turns to tighten them down.  I will definitely be hunting down silver metal pinstriping tape to fill them.

The pair were resolving brighter stars across the core of M22.  The Cassini division and a band on Saturn were easily visible.  Multiple bands on Jupiter were seen despite the magnification being a bit high for the seeing conditions tonight.  Star fields were sharp across the field with no visible edge of field brightening (EOFB).

Overall, they were a delight to use together as I had suspected based on monoviewing.  Having paid about $50 for the pair with sales tax, I'm very happy with them.  They have kicked my 19mm Konig binocular eyepiece pair out of my bino case.  The SVBONYs were far and away better.  They are highly recommended if you binoview at long focal ratios with eyeglasses.

[Zermelo]

@wookie1965 looks like you just bought a good'un - have you had chance to use it yet?

[wookie1965]

1 hour ago, Zermelo said:

@wookie1965 looks like you just bought a good'un - have you had chance to use it yet?

No not yet not had any clear weather and the forecast for the next few days is rubbish.

Paul