SVBony

SVBony SV190 Ultra Flat Field 18mm

Name: SVBony SV190 Ultra Flat Field 18mm
Brand: SVBony
Price: 80.09 USD
Availability: InStock

Sixty five degrees of flat field with 20 millimetres of eye relief, which is the specification people pay two to three times as much for. The best single deep sky eyepiece in this catalogue under a hundred dollars.

83/ 100

Polaris Score

Optical quality · Immersion · Comfort · Value

See the breakdown ↓

What it's for

Low power · wide fieldHigh power · narrow field

A low to medium power eyepiece, which in most telescopes lands between 27x and 113x. That is the range where galaxies, nebulae and globular clusters look their best: enough magnification to show structure, enough field to hold the whole object.

Apparent Field

65°

Barrel Size

1.25"

Eye Relief

20mm

Focal Length

18mm

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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.

65° apparent field

At 65°, you are aware of the field edge, like looking down a short, comfortable tube.

Try this eyepiece on your own scope in the Simulator →

01What it's good at

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

Twenty millimetres of eye relief across a 65 degree field is a genuinely glasses-friendly combination, and it is rare below three figures.

Best at

✓Twenty millimetres of eye relief across a 65 degree field is a genuinely glasses-friendly combination, and it is rare below three figures.

✓The eight element design holds the field flat, which matters most in the fast Dobsonians and refractors where budget eyepieces usually fall apart at the edge.

✓In an eight inch Dobsonian it frames 58 arcminutes, just under a full degree, which holds almost every Messier object whole while still magnifying enough to show structure.

Trade-offs

!Sixty five degrees is wide and not immersive. If you have used an 82 degree eyepiece you will feel the field stop.

!Eight elements in five groups means more glass surfaces than a simple design, and on bright targets close to a bright star you can find slightly more scattered light than a premium coating would allow.

!The mechanical finish is functional rather than refined, and the eyepiece is noticeably heavier than the Plossl it replaces, which can upset the balance of a small Dobsonian.

02In your telescope

One eyepiece. A different job in every scope.

27× in a small refractor, 113× in a long SCT

An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 27× and 2.4° of sky in a little refractor, or 113× 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

27×

True field

2.4°

Exit pupil

3.3 mm

In a 480mm apo this delivers 27x over 2.4 degrees, a rich field setting that sweeps the Milky Way and frames the largest open clusters entire.

8-inch Dobsonian

1200 mm · f/6

Magnification

67×

True field

58′

Exit pupil

3.0 mm

In an eight inch Dobsonian it gives 67x across 58 arcminutes with a 3mm exit pupil, which is close to the ideal general purpose deep sky setting for that telescope.

12-inch Dobsonian

1500 mm · f/5

Magnification

83×

True field

47′

Exit pupil

3.6 mm

In a twelve inch Dobsonian it reaches 83x with a 3.6mm exit pupil, bright and wide enough to show spiral structure in the brighter galaxies while holding them whole.

8-inch SCT

2032 mm · f/10

Magnification

113×

True field

35′

Exit pupil

1.8 mm

In an eight inch Schmidt-Cassegrain it produces 113x over 35 arcminutes, a useful power for globular clusters and planetary nebulae though the field is tighter than the same eyepiece gives elsewhere.

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.

18mm FL · 65° AFOV · 1.25"

Eye reliefGlasses friendly

20 mm

Twenty millimetres is the threshold at which an eyepiece becomes genuinely usable with spectacles on, which matters if you have astigmatism that the telescope cannot correct for you. Even without glasses it changes the experience: you rest your eye at a comfortable distance rather than pressing into a cup, and the view stops swimming every time you breathe.

Apparent fieldWide

65°

This is the size of the circle of view as it appears to your eye. Sixty five degrees is comfortably past the 52 degrees of a Plossl, which is where most people first notice that an eyepiece feels like looking out rather than looking through. It stops short of the 82 degree class, where the field edge moves outside your attention entirely.

Focal lengthLow to medium power

18 mm

Divide this into your telescope's focal length for magnification: 27x in a small apo, 67x in an eight inch Dobsonian, 113x in an eight inch Schmidt-Cassegrain. That middle figure is the most useful number here, because 67x paired with a 58 arcminute field is close to the ideal setting for browsing the Messier catalogue.

Optical designComplex

8 elements in 5 groups

Eight elements is a lot of glass for an eyepiece at this price, and it is what delivers a flat field across 65 degrees together with long eye relief. The trade is more air to glass surfaces, each of which scatters a little light, so this design depends on its multi-coatings more than a simple Plossl does.

Exit pupil rangeDeep sky ideal

1.8 to 3.6 mm

Exit pupil is the width of the light beam reaching your eye, and around three millimetres is where deep sky observing works best: the object is magnified enough to show structure while the sky background stays dark. In a fast Dobsonian this eyepiece sits right in that window, which is the main reason it will live in your focuser.

04What comes alive

The targets this eyepiece was born for.

The Orion Nebula (M42), The Hercules Cluster (M13), The Andromeda Galaxy (M31), The…

Comes alive

The Orion Nebula (M42)

At 67x the wings spread across the field and the Trapezium resolves cleanly at the centre.

Comes alive

The Hercules Cluster (M13)

Enough magnification to resolve the outer stars into points while the whole cluster still sits comfortably inside the field.

Excellent

The Andromeda Galaxy (M31)

Too large to frame whole in most telescopes, but this shows the bright core and the dust lane with the companions in view.

Excellent

The Whirlpool Galaxy (M51)

At 67x to 83x in a larger Dobsonian the two cores separate and the bridge between them becomes visible under dark sky.

Comes alive

The Dumbbell Nebula (M27)

Bright, large and perfectly suited to this power, with the apple core shape obvious even without a filter.

Excellent

The Pleiades (M45)

Frames whole in a short refractor at 27x, which is the way this cluster is meant to be seen.

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

18 mmThis one

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

7 mm

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

An eight inch Dobsonian

67x with a 58 arcminute field is arguably the single most useful eyepiece setting this telescope has.

A short apo refractor

At 27x and 2.4 degrees this becomes a rich field instrument for sweeping the summer Milky Way.

Pair it

What to own alongside

SVBony SV190 Ultra Flat Field 10mm

Between the two you have deep sky and planetary covered from one line, with consistent eye relief and field behaviour.

SVBony SV154 Super Wide Angle 26mm

If your focuser takes 2 inch eyepieces, this adds the low power wide field end that an 18mm cannot reach.

Filter it

What helps at this power

SVBony UHC 1.25 inch

This is the focal length where a UHC pays off most: it darkens the background on the Veil and the North America Nebula without dimming the stars into nothing.

An OIII filter

For planetary nebulae specifically. At 67x the Ring and the Dumbbell both gain contrast that a broadband filter cannot deliver.

07The Polaris Score

How it scores, and why.

83/100

83/ 100

SVBony SV190 Ultra Flat Field 18mm

Sixty five degrees with 20mm of eye relief and a genuinely flat field is a combination that normally appears at three times this price. It earns a strong score on capability and value and stops short of the top of the range on finish, coatings and the last few percent of edge correction that the premium lines still hold.

Optical quality

Immersion

Comfort

Value

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.

Someone building a small set of good eyepieces who wants the one that will get used most…

Buy it if you

✓Someone building a small set of good eyepieces who wants the one that will get used most nights.

✓Observers with fast telescopes who have noticed their existing eyepieces smearing stars at the edge and want that to stop.

✓Anyone who observes wearing glasses, because 20 millimetres of eye relief comfortably clears most prescriptions with the eyecup folded down.

✓Deep sky observers under moderately dark skies, where a 3mm exit pupil is close to the ideal balance of image scale and background darkness.

Look elsewhere if you

!Planetary specialists, who want twice this magnification and should look at the 10mm in the same line.

!Observers who have already tasted an 82 or 100 degree field, where returning to 65 degrees feels like putting the walls back.

!Anyone with a very long focal length Schmidt-Cassegrain used mostly for planets, where 113x from an 18mm is an awkward middle power.

!Collectors of premium glass, who will notice this line's coatings and mechanical finish sit below what Tele Vue and Pentax deliver.

09The numbers

Full specifications.

6 measured and stated values

Optical

Focal Length18mm

Apparent Field65°

CoatingsFully multi-coated

Comfort & handling

Eye Relief20mm

Fit & build

Barrel Size1.25"

More

lens design8 elements in 5 groups

Editor’s Take

There is a particular class of eyepiece that quietly ends the upgrade itch: wide enough that you stop noticing the edge, comfortable enough that you stop noticing your eye, and corrected well enough that you stop noticing the optics. It usually costs three hundred dollars. This one is eighty nine, and while it is not the equal of the premium glass in coatings or finish, the thing it does for your observing is the same thing. If you buy one eyepiece to live in your focuser, buy this focal length.