Svbony 8-3 zoom

[RT65CB-SWL]

1 hour ago, Don Pensack said:

Look up a Baader Contrast Booster filter to see more details on Mars.

...

Even a Baader Neodymium and/or a #23A filters should bring out some details of Mars.

[Louis D]

And if your budget won't stretch to Baader prices, see my recent post below:

You can pick up cheap M&SG filters on ebay UK for under £5 shipped direct from China.  Same goes for cheap yellow filters.  For under £10 you can get an idea of what the Baader Contrast Booster can do when the two are stacked together.

[Ratlet]

Thanks for the tips folks.  @Louis D I've ordered the cheap ebay ones, if nothing else it'll be interesting to see what they do.  @Don Pensack thanks for the information about where those reflections are coming from.  I didn't really think about the source and just assumed it was reflecting inside the lenses somewhere, but in hindsight the rapid motion does suggest an eyeball effect at play.

[Ratlet]

We are currently in between two storm fronts, with last night being pretty windy and the weekend being potentially even worse, however tonight is quite clear so far, and seeing Jupiter and Mars in the twilight sky I grabbed the SVBONY 3-8mm zoom and my 8mm BST and the x2 ED barlow with my 130PDS.

Jupiter was up first and I have to say even without having the eyepiece to do a side by side, the contrast was obviously improved with the SVBONY at 8mm vs the Starguider.  The equatorial bands had more colour to them and they also appeared sharper.  Try as I might I just couldn’t get the Starguider to show as sharp delineation between the banding as the SVBONY.  The SVBONY was even better at 4mm compared to the barlowed 8mm.  Contrast was still improved and there was a much better feeling of being in focus.  More of a snap to focus where as the Starguider kind of wallowed through focus but didn’t feel as sharp even at its best.  I did get some blackouts with the Starguiders, but none at all with the svbony.

I didn't spend much time on mars as the wind was starting to pick up and the daughter wanted a look at Jupiter.  However I found the colour much more satisfying the the svbony.  It was a very deep red orange, whilst the Starguider and Barlow is much brighter, more of a white orange.

 As has been mentioned the SVBONY is not parfocal through its focal lengths, however the adjustments required for best focus are tiny and I mostly used the fine adjustment to correct and was within the range of my usual futzing with focus.  It didn’t feel onerous at any rate.

The eyecup is weird.  It almost feel like they want you to push your eye into it.  It certainly felt like I needed to be very close, especially at the shorter focal lengths.  The Starguiders certainly have the advantage on eye relief.  I’ll see how I get on, but I suspect it will be spending most of the time folded over, which won't be an issue for it as it is very soft and squishy.  There is a thread under the eyecup.  Not sure what it's for or what size it is, but there is one there.

The barrel on the eyepiece is very long and playing with how far into the focuser it feels like it could have done with a bit more body and a bit less length.  Fortunately I've got some parfocal rings so I'll add that when I get a chance.

Just because I had the barlow out I decided to try it out and it barlowed well with no loss of contrast at comparable focal lengths.

Hopefully it will remain clear.  If it does I’m going to nip out again.  GRS should be transiting shortly and I’ve yet to see it. (Update:. It didn't stay clear)

I think, as a rank amateur, this zoom represents a pretty good option for people starting out who are looking for a planetary eyepiece.  It's very comfortable to use and has, to me, great views.  It's a very nice experience just changing to focal length the test where the sweet spot of the seeing is.  A lot easier than changing eyepieces!  It feels very good quality and the click stops when you change focal length makes it very easy to tell where you are.

Edited January 6, 2023 by Ratlet
Added some more detail.

[Whistlin Bob]

On 01/01/2023 at 15:38, Louis D said:

I was out observing the moon last night with my 8" Dob without coma corrector (to eliminate its SA), the 3-8mm Svbony zoom, and the 5-8mm Speer-Waler varifocal

I have to say this really is an excellent review. I think any experienced observer would glean a lot of information from it and have a very good idea if what they're getting. 

[Zermelo]

I finally got around to doing a review, here:

https://stargazerslounge.com/topic/406326-svbony-sv215-3-8mm-planetary-zoom/

 

[Don Pensack]

2 hours ago, Zermelo said:

I finally got around to doing a review, here:

https://stargazerslounge.com/topic/406326-svbony-sv215-3-8mm-planetary-zoom/

 

I'd like to clarify a few terms after reading your review:

Ghosting is when internal reflections in the eyepiece for a bright object (like a planet) being viewed result in a slightly fainter image of the same object entering the opposite side of the field, and drifting across the field in the opposite direction the object is drifting,

crossing in the center, and exiting the side opposite the side the bright object is exiting.

Reflection is when a bright object reflects from the cornea back into the eyepiece and is, in turn, re-reflected back at the eye.  Moving the head or eye causes the reflection to move all over the place.

Glare is when a bright object immediately outside the field causes bright spikes, loops or flares inside the field of the eyepiece.

Light scatter is when the field around the object is awash with light from the bright object, but internally scattered in the eyepiece due to poor coatings or rough lens surfaces.

 

Your pictorial example is that of light scatter, not ghosting, unless the out of focus bright image drifts in the opposite direction as the planet as it drifts across the field, but with the head held steady.

[Zermelo]

9 hours ago, Don Pensack said:

Ghosting is when internal reflections in the eyepiece for a bright object (like a planet) being viewed result in a slightly fainter image of the same object entering the opposite side of the field, and drifting across the field in the opposite direction the object is drifting,

crossing in the center, and exiting the side opposite the side the bright object is exiting.

I've read several descriptions of ghosting, which is why I wanted to be clear with mine.

I didn't observe the effect in quite the way you describe, because my mount was tracking, but I'll try turning it off next time I'm out.

Although I'm sure that what I'm seeing is derived from the bright object in view, I have never seen it as a duplicate image of the same size, or with any detail corresponding to the original object. It is always somewhat larger, and in some cases approaches the size of the entire field. But it always has the behaviour of moving in the opposite direction of eye movement.

9 hours ago, Don Pensack said:

Reflection is when a bright object reflects from the cornea

Ah, OK. So what I'm seeing is not the result of external corneal reflection, just internal.

9 hours ago, Don Pensack said:

Your pictorial example is that of light scatter, not ghosting, unless the out of focus bright image drifts in the opposite direction as the planet as it drifts across the field, but with the head held steady.

I lifted that simulation from a CN thread on ghosting. I suppose it actually shows both scatter and ghosting. The disc-shaped, off-centre effect is what I'm referring to as ghosting, but the diffuse, edgeless glow, symmetrical about Jupiter, is the scatter.

Thanks for your comments, Don.

[Louis D]

Lack of tracking definitely reveals more details about stray light control than having tracking.  For instance, when I move a bright star center to edge in my 127 Mak with a 2" visual back and widest field 40mm SWA eyepiece, I can see a reflection off some baffle tube in the scope revealing itself as a hollow, oval reflection of the star on the opposite side of the FOV that grows in size the further off axis I move the star.  If I had kept the star centered, I would have never noticed it.  If I had kept the star stationary off axis, I might never have made the connection as to what was causing the oval reflection on the opposite side of the FOV.

I'm always moving objects, sometimes rather rapidly, center to edge to observe changes to the FOV during eyepiece and telescope evaluations.  My eyes can pick up moving changes way easier than static details.

[Zermelo]

I've just noticed, while revisiting Ernest's review of the SV215, that he has updated it (on Feb 26th) with a second review.
He has now obtained a production release specimen (the original review was based on a pre-production sample).
The new review is posted immediately below the original one in this thread (English, translated from Russian).

He has expanded the table of nominal vs measured attributes, to cover the additional click-stops on the production model. Also, some of the measured values for those focal lengths that were included in the first report have changed in the new one.

The concluding assessment now reflects the production version, and is more positive in some respects than the original review:

"The glare noted in the pre-production sample has ceased to appear, light scattering still seems to me increased, eye relief is still not the most comfortable. Interestingly, the angular field of view of the eyepiece, as well as the diameter of the effective aperture, is slightly larger than stated. But the real focal length of the eyepiece (and, accordingly, the increase) at the short-focus end does not fall far short of 3 mm.
...

The mechanics of the serial sample has been noticeably altered: the landing sleeve has been shortened, intermediate stops have appeared at 7 and 5 mm focal lengths, and the distance that the eyepiece extends during zooming has been reduced. The optics remained almost the same, although the enlightenment seems to have been improved. In general, the eyepiece is quite worthy to be at hand for the owner of a moderately fast telescope when observing the planets. I recommend"

[Louis D]

His numbers pretty well agree with what I measured.

• Sharpness is excellent from 8-5mm with falloff below that.
• Focal lengths were pretty accurate for 8-5mm, with 4mm being off a bit (4.3mm) and 3mm being 3.5mm.
• Eye relief decreasing from 11mm to 6mm going from the 8mm setting to the 3mm setting seems about right.  I just couldn't measure it accurately with the limitation of my methodology.

Where we noticeably diverge is for AFOV:

• AFOV for me was 8mm=58°, 7mm=59°, 6mm=59°, 5mm=60°, 4mm=61°, 3mm=61°, so a nice, almost linear progression in size increase.
• I did not detect any of the decreasing, increasing, decreasing AFOV going from 8mm to 3mm with a minimum at 6mm of 55.5°.

I re-edited my AFOV image to more dramatically show how the AFOV increases from 8mm to 4mm in a fairly smooth manner, and then remains constant to 3mm:

This doesn't fit with Ernest's numbers very well:

3

4

5

6

7

8

58.9

61.3

57.3

55.5

56.5

58

Edited March 15, 2023 by Louis D

[Zermelo]

3 hours ago, Louis D said:

Where we noticeably diverge is for AFOV:

• AFOV for me was 8mm=58°, 7mm=59°, 6mm=59°, 5mm=60°, 4mm=61°, 3mm=61°, so a nice, almost linear progression in size increase.
• I did not detect any of the decreasing, increasing, decreasing AFOV going from 8mm to 3mm with a minimum at 6mm of 55.5°.

I'm not sure that Ernest has a magic ruler, though.

[Ags]

Despite having started this thread, I am a bit late to the party - mine is now ordered and should arrive in a couple of weeks.

[Shimrod]

On 26/03/2023 at 00:00, Ags said:

Despite having started this thread, I am a bit late to the party - mine is now ordered and should arrive in a couple of weeks.

I ordered mine last week after dithering for a while - bought the last one from an Ebay seller at £105. Not had a chance to use it and this is my first zoom eyepiece, but it clicks nicely into place as you zoom and feels well put together. I am hoping it will go well with my ZS61 to make my travel kit a bit lighter.

[nicholasastro]

On 27/03/2023 at 18:45, Shimrod said:

I ordered mine last week after dithering for a while - bought the last one from an Ebay seller at £105. Not had a chance to use it and this is my first zoom eyepiece, but it clicks nicely into place as you zoom and feels well put together. I am hoping it will go well with my ZS61 to make my travel kit a bit lighter.

I don't think you will be disappointed. I have had mine for a couple of months now and have been impressed by the sharp and high contrast views of Mars, which were good enough not to be tempted to pull out my 3.4mm Vixen HR and 4mm TMB Supermonocentric on nights of good seeing. I'm not saying the zoom is better or even equal but I do think it is very good.

[Jim L]

On 25/03/2023 at 17:00, Ags said:

Despite having started this thread, I am a bit late to the party - mine is now ordered and should arrive in a couple of weeks.

I think you’ll enjoy it.  

I had my own Sv215 3-8mm zoom out last evening looking at the moon through it and a 50mm f/5 achro doublet.  Conditions were so-so, with high thin clouds and high winds conspiring against good seeing, but the little scope on its photo tripod is so easy to deploy it often goes out when I wouldn’t commit to taking out a larger scope.

The views through the scope are always surprisingly good for its quite modest aperture and last night was no exception.  I found the 5mm setting on the zoom to be good at the time, and remembering I have a newish 5mm T6 Nagler thought a quick and dirty non-scientific comparison might be fun.

I picked the particularly sharp ridge top of a convenient crater near the terminator as my target of comparison.  Swapping the two eyepieces back and forth I was surprised that on and near center the Sv215 zoom was every bit as sharp and crisp as the Nagler, and that it was also perhaps a bit brighter.  I swapped enough times to be pretty sure of my observations, and while somewhere in the back of my mind I hoped that the Nagler would prove superior, at that time, for that target, through that scope, and under those conditions, it wasn’t.

Long story short, the Sv215 zoom is a pretty good short focal length zoom eyepiece, and especially so for the price.  Along with a Sv135 7-21mm zoom and a 32mm Plössl, the three eyepieces make a simple, compact, and versatile combination for a fast refractor.

[Jim L]

I just remembered that the barrels of the Sv215 zoom and Nagler 3-6mm zoom eyepieces are long enough to make contact with the optical components of several 1.25” diagonals, including the Takahashi prism diagonal, the Baader T-2 Zeiss spec prism diagonal, and the Baader T-2 BBHS mirror diagonal.

As far as I can tell none of the diagonals I just mentioned have an effective safety stop within the eyepiece holder tube, and the SvBony and TeleVue zoom eyepieces may hit glass if measures aren’t taken to prevent contact. There are probably other diagonals that are similarly unprotected.

Parafocal rings can be installed on the zoom eyepiece barrels and are an inexpensive and effective solution to this potentially expensive problem.

 

[Jim L]

Here’s a parafocal ring in action for those of us who might not have seen one in the wild.  The parafocal ring reduced the inserted eyepiece barrel length from a prism smashing 36.7 mm, to the quite safe 29 mm shown. You can get a set of three rings from FLO here:

https://www.firstlightoptics.com/adapters/astro-essentials-parfocal-rings.html

[Ratlet]

1 minute ago, Jim L said:

Here’s a parafocal ring in action for those of us who might not have seen one in the wild.  The parafocal ring reduced the inserted eyepiece barrel length from a prism smashing 36.7 mm, to the quite safe 29 mm shown. You can get a set of three rings from FLO here:

https://www.firstlightoptics.com/adapters/astro-essentials-parfocal-rings.html

Quite handy things to have all told, and unlike most astro things they don't cost the earth.

I use mine to do this and make a slightly beefier collar for my laser collimator.

[Ags]

I had a very brief first glimpse in some scurrying cracks in the cloud. Only a few seconds at each zoom setting, but I think I will like this eyepiece. Firstly I found eye relief behaved well at infinity focus - I had found earlier when focusing on a much closer stairwell that the eye relief at 3 mm got eyelash-crushing tight. I was keeping the eyecup rolled down. Secondly, in my 500 mm scope the 8 mm setting frames the whole Moon nicely, with what seemed like good sharpness. The zoom adjusts nicely between the settings but two hands are needed. With my eyes, and in an f5.6 scope, I need to refocus for the 3-4 mm settings, when dialing in from the 8 mm setting. At 3 mm the Moon possibly looked glorious, but the clouds were in the ascendant and I quickly lost the image. A very nice eyepiece for small refractors.

Also, the field of view seems much larger than 56 degrees, it felt “widefield” if that makes any sense.

[RT65CB-SWL]

I will confess that since I ordered and received mine, I have not had chance to try mine out or use my ‘scopes due to my shift pattern and the GB/UK 🇬🇧 weather… ie clear skies when I am working… cloudy/overcast on my rest days. 

Good to see this topic is having good following and response. 

Edited April 8, 2023 by Philip R

[Louis D]

14 hours ago, Ags said:

Also, the field of view seems much larger than 56 degrees, it felt “widefield” if that makes any sense.

Photographically, I found the AFOV to vary from 58 to 61 degrees, so it qualifies as widefield, just not super wide field (SWA) which generally starts at 65 degrees.

6mm and 7mm are clearly different in AFOV.  I went back and remeasured my photos.  Sure enough, I was off on the 6mm for some reason.  It actually works out to a 59.7 degree AFOV at 6mm.  Mea culpa.

[Ags]

AFOV might be 61 degrees at 3 mm but while observing theSun today I couldn’t actually see more than 30 degrees due to the infernal eye relief. No issues at 4 mm and wider.

[LDW1]

3 minutes ago, Ags said:

AFOV might be 61 degrees at 3 mm but while observing theSun today I couldn’t actually see more than 30 degrees due to the infernal eye relief. No issues at 4 mm and wider.

Be happy then with 4mm, whats 1mm in a view that high powered, especially the sun.

[Ags]

The 3 mm setting is key for me; it will get plenty of use on doubles and Luna, assuming I can find a way to get close enough to the eyepiece!