SVBony Redline 9mm Ultra Wide Angle — image 1
SVBony

SVBony Redline 9mm Ultra Wide Angle

The best eyepiece in the most recommended budget set in amateur astronomy, and the one focal length of the four that holds up in a fast telescope. If you buy one goldline, buy this one.

81/ 100
Polaris Score
Optical quality · Immersion · Comfort · Value
See the breakdown ↓
What it's for
Low power · wide fieldHigh power · narrow field

A medium to high power eyepiece. In most telescopes it lands between 50x and 230x, which covers planets, the Moon, double stars, globular clusters and small planetary nebulae. It is not a wide field eyepiece for large nebulae, which need something around 20mm or longer.

Apparent Field
68°
Barrel Size
1.25"
Eye Relief
15mm
Focal Length
9mm
From$40.99

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The spacewalk

You don’t look at a field.
You look into the sky.

Every number on the spec sheet matters less than one feeling: how much sky wraps around your eye. Widen the apparent field and watch the black edge of the eyepiece slip away.

68° apparent field

At 68°, the black rim sits out at the corner of your attention rather than in front of you.
Try this eyepiece on your own scope in the Simulator →
01What it's good at

What it's best at — and the trade-offs.

Six elements in four groups against four or five in the rest of the line, and it is the reason this focal length outperforms its siblings rather than…
Best at
✓Six elements in four groups against four or five in the rest of the line, and it is the reason this focal length outperforms its siblings rather than matching them.
✓Correction holds in telescopes as fast as f/3.5, which is unusual at any price under about a hundred dollars and almost unheard of under forty.
✓Around 15mm of eye relief at 9mm focal length, where a Plossl of the same power gives you six and pushes your eyelashes into the glass.
Trade-offs
!Coatings and internal blackening are basic, so a bright object just outside the field can throw a visible ghost across the view.
!The marketing field is 68 degrees but the measured field across this design varies by focal length, and the honest number here is closer to 70 than to 68. It is a good surprise rather than a bad one, but the spec sheet is not precise.
!Build is plastic-heavy and the eyecup is unremarkable. This is a value tool, and it looks and feels like one next to mid-range glass.
02In your telescope

One eyepiece. A different job in every scope.

53× in a small refractor, 226× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 53× and 1.3° of sky in a little refractor, or 226× and a tight frame in a long SCT. Here’s what it does across common scopes.

Small apo refractor
480 mm · f/5.5
Magnification
53×
True field
1.3°
Exit pupil
1.6 mm
In a 480mm apo refractor this gives 53x across 1.3 degrees, a wide, bright, easy view that works as a general sweeping power and frames the whole of the Pleiades with room around it.
8-inch Dobsonian
1200 mm · f/6
Magnification
133×
True field
31′
Exit pupil
1.5 mm
In an eight inch Dobsonian it lands on 133x with a 31 arcminute field, almost exactly the width of the full Moon, which is the classic planetary power for this aperture and the reason this focal length gets recommended so often.
12-inch Dobsonian
1500 mm · f/5
Magnification
167×
True field
24′
Exit pupil
1.8 mm
In a twelve inch Dobsonian it reaches 167x with a 1.8mm exit pupil at f/5, and this is the combination where the eyepiece earns its reputation, because most rivals at this price visibly smear the outer field in an f/5 scope.
8-inch SCT
2032 mm · f/10
Magnification
226×
True field
18′
Exit pupil
0.9 mm
In an eight inch Schmidt-Cassegrain it produces 226x across 18 arcminutes with a 0.9mm exit pupil, real planetary magnification that will only pay off on a steady night.
Exit pupil is how wide the beam of light leaving the eyepiece is. Around 5–6 mm is bright and immersive under dark skies; push much past 6 mm and you waste light, and under light pollution a smaller exit pupil shows more contrast.
03In plain English

The numbers, in plain English.

9mm FL · 68° AFOV · 1.25"
Optical designThe most glass in the line
6 elements in 4 groups
The four focal lengths in this family are not one design scaled up and down. This one uses six elements where the 15mm uses four, and that extra pair of surfaces is doing correction work at the edge of the field. It is why this eyepiece stays clean in a fast telescope and its 15mm sibling does not. When reviewers rank the set, this focal length comes first, and the element count is the reason.
Eye reliefComfortable
15 mm
This is how far behind the lens your eye can sit and still see the whole field. A 9mm Plossl gives you about six millimetres, which means pressing your eye socket to the glass and fogging it with every breath. Fifteen millimetres comes from a built-in Barlow group ahead of the eye lens, and it is what makes this focal length pleasant to use for an hour rather than a minute. Note that SVBONY's own spec table prints 17mm for all four focal lengths in the set, which is a copy and paste error. The per focal length figures published for the identical Agena badged version are the ones to trust.
Apparent fieldWide
68° (measured nearer 70°)
This is how large the circle of view appears, and it is the number that separates a wide field eyepiece from a kit Plossl at 52 degrees. Sixty-eight degrees is enough that you have to move your eye to take in the edge, which is the point at which a view starts feeling like a window rather than a tube. Independent measurement of this focal length comes out slightly wider than the label, unlike the 6mm, which measures narrower.
Focal ratio toleranceUnusual at this price
Holds to about f/3.5
A fast telescope sends light into the eyepiece at a steep angle, and cheap wide fields respond by turning edge stars into small commas or seagulls. Most budget wide fields start showing this below f/6. This one has been tested in f/3.5 instruments and holds. If you own a fast Dobsonian or a short refractor, this is the single most important line on the page.
Barrel and filter threadStandard
1.25 inch, threaded
It fits every focuser and diagonal that takes a 1.25 inch eyepiece, which is effectively all of them, and the front is threaded for standard 1.25 inch filters. At this power a Moon filter is the one worth owning, since the Moon at 130x in an eight inch scope is genuinely too bright for a dark adapted eye.
04What comes alive

The targets this eyepiece was born for.

Jupiter and its moons, Saturn, The Moon at the terminator, M13 and the brighter globulars…
Jupiter and its moonsComes alive
Jupiter and its moons
At 130x to 230x the two main belts, festoons along their edges and the Great Red Spot separate, with the moons strung out in the same field.
SaturnComes alive
Saturn
This is roughly where the Cassini division stops being a suspicion and becomes a visible gap.
The Moon at the terminatorComes alive
The Moon at the terminator
Crater walls, central peaks and hard shadows, with a field wide enough to drift along the terminator rather than chase it.
M13 and the brighter globularsExcellent
M13 and the brighter globulars
At this power the outer core starts breaking into individual stars instead of a grainy ball.
The Ring Nebula (M57)Excellent
The Ring Nebula (M57)
A small planetary that wants magnification. The smoke ring opens up and the sky around it darkens.
Excellent
Tight double stars
Clean splits of colourful pairs, and a good test of how honest the on-axis optics are.
05Role in a collection

Where it sits in your eyepiece case.

Where it sits across 3 focal lengths

A good eyepiece collection isn’t a pile of glass — it’s two or three focal lengths that hand off from wide to tight. This is the anchor at the bottom of the ladder: the one you find and frame with. You buy it once, and it stays your low-power eyepiece for life.

32 mm
Low power · wide field
Find, frame and sweep. Your widest true field and the lowest useful magnification — the eyepiece you reach for first.
Veil Nebula · Pleiades · Milky Way star clouds
13 mm
Medium power · the workhorse
Where most deep-sky objects look their best — galaxies, globulars and planetary nebulae at a comfortable scale.
M13 · Ring Nebula · most galaxies
9 mmThis one
High power · detail
Planets, the Moon at the terminator, tight double stars and the smallest planetary nebulae. Steady-air nights only.
Jupiter · Saturn · lunar craters
06Build around it

What it pairs with.

The telescope · Pair it · Filter it
The telescope
Where this focal length works
A fast Dobsonian at f/4 to f/5
This is the pairing the eyepiece is famous for. It holds correction where cheaper wide fields smear the outer field.
An eight inch SCT or a Maksutov
Slow optics are the easiest case for any eyepiece, and here 9mm gives you serious planetary power for the price of a pizza.
Pair it
What to own alongside
SVBony Redline 20mm Ultra Wide Angle
SVBony Redline 20mm Ultra Wide Angle
The natural partner from the same set, and the second best of the four. Together they cover most of a night.
A 2x Barlow
Turns this into a 4.5mm for the rare nights when the seeing supports it, and saves buying the weaker 6mm.
Filter it
What changes the view
A Moon filter
At 130x in an eight inch scope the Moon is bright enough to spoil your dark adaptation for the next twenty minutes.
SVBony UHC 1.25-inch
SVBony UHC 1.25-inch
Threads into the barrel and lifts the contrast on the small planetary nebulae this power suits.
07The Polaris Score

How it scores, and why.

81/100
81/ 100
SVBony Redline 9mm Ultra Wide Angle

Scored as the strongest member of a budget line, not as a premium eyepiece. It earns a high mark for holding correction in fast telescopes, which is the thing budget wide fields normally fail at, and for pairing a wide field with eye relief that does not force your eye onto the glass. It is held back by coatings, build and stray light control that are visibly a tier below mid-range glass.

Optical quality
80
Immersion
83
Comfort
83
Value
95

Polaris weighs how well the eyepiece does the job it was designed for — optics, immersion, comfort and value — never list price or brand.

08Who it's for

An honest fit check.

Anyone building a first eyepiece set who wants one focal length that will still be worth…
Buy it if you
✓Anyone building a first eyepiece set who wants one focal length that will still be worth owning after they upgrade everything else.
✓Owners of fast telescopes, f/4 to f/5 Dobsonians and short refractors, where most budget wide fields smear the outer field and this one largely does not.
✓Observers who want a real wide field view of the Moon and planets without paying mid-range prices for it.
✓Anyone who has read the forum recommendation and wants to know which of the four focal lengths actually deserves it.
Look elsewhere if you
!Observers who already own good mid-range glass around this power, where the gain would be backwards rather than forwards.
!Anyone hunting large deep sky objects, which need a low power wide field rather than 130x to 230x.
!Observers who want premium stray light control, since this eyepiece will throw a reflection when a bright object sits just outside the field.
!Anyone expecting the build quality to match the optics, because it does not.
09The numbers

Full specifications.

7 measured and stated values
Optical
Focal Length9mm
Apparent Field68°
CoatingsFully multi-coated
Comfort & handling
Eye Relief15mm
Fit & build
Barrel Size1.25"
More
lens design6 elements in 4 groups
weight g190
Editor’s Take

Ask a forum what to put in a new Dobsonian and somebody will say goldline within three replies. They are right, but they are usually right about this eyepiece specifically. The 9mm carries six elements where its siblings carry four or five, and the extra glass shows: it stays sharp in scopes down to f/3.5, where the 15mm falls apart and the 20mm starts to smear. Under forty dollars it is not a compromise you tolerate. It is a genuinely good eyepiece that happens to be cheap.

— The Skynocular verdict
10Alternatives

For a different goal, start here.

3 alternatives, each mapped to the goal it wins at
The partner

SVBony Redline 20mm Ultra Wide Angle

The other focal length in this set worth owning. A 9mm and a 20mm cover planetary and most deep sky between them without a third eyepiece.

→
The step up

Explore Scientific 68° Series

The same field, argon purged and waterproof, better corrected and better built, for roughly four times the money.

The same eyepiece

Agena 1.25" Enhanced Wide Angle 9mm

The gold ringed badge of this exact design, sold by Agena. Same element count, same field, same optics. Buy whichever is cheaper on the day.