SVBony

SVBony SV216 2x Barlow Lens

2x Barlow · 4 elements · 1.25 inch · W9168A

Doubles the magnification of any eyepiece you put in it, so a two-eyepiece kit behaves like a four-eyepiece one. Four elements rather than the usual two, which is why it holds up at high power.

80/ 100

Polaris Score

The four-element Barlow at a two-element price

From$59.99

Where to buy

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What problem does this solve?

Two eyepieces, four magnifications.

Eyepieces are the expensive part of a telescope kit, and the magnifications you want are not evenly spaced. Most people end up with a low power finder eyepiece and a mid power one, and then discover the planets want something shorter still, which is another purchase at another eighty dollars.

A Barlow multiplies the magnification of whatever eyepiece sits in it. A 2x in front of an 18 mm makes it behave like a 9 mm, and in front of a 10 mm makes it a 5 mm. Two eyepieces plus a Barlow gives four working magnifications, and it does so while keeping the comfortable eye relief of the longer eyepiece, which a genuinely short eyepiece would not.

You need one if

You need one as soon as your shortest eyepiece is not reaching the magnification the planets deserve on a steady night.

You can skip it if

Skip it if you observe only deep sky at low power, where doubling magnification halves the field and darkens the image for nothing you wanted.

How it actually works

What the setup looks like.

A Barlow is a diverging lens that sits before the eyepiece and stretches the light cone. Using one is simple, with one thing worth knowing:

Drop it into the focuser

The 1.25 inch barrel goes where an eyepiece normally sits, held by the focuser's own thumbscrew.

Put the eyepiece into the Barlow

Three thumbscrews and a compression ring hold it without marking the barrel, which matters if your eyepieces are the expensive kind.

Refocus

A Barlow shifts the focal point outward, so expect to rack the focuser in noticeably from where the eyepiece alone focused.

Judge the night, not the eyepiece

Doubling magnification also doubles how visible the atmosphere's turbulence is. On a poor night the un-Barlowed view will be the better one.

The filter thread on the front takes standard 1.25 inch filters, so a Moon filter can live on the Barlow rather than being moved between eyepieces.

01Will it fit my setup

Compatibility.

What this accessory works with — check the fit before you check the price.

Any 1.25 inch eyepiece1.25 inch focusers and star diagonalsPlanetary cameras with a 1.25 inch nosepieceStandard 1.25 inch filters on the front thread

Note✕1.25 inch only, so a 2 inch eyepiece will not fit✕Doubling magnification halves the true field and dims the image✕Adds length to the train, so a short-travel focuser may run out✕At 219 grams it is heavy, and with an eyepiece on top can unbalance a light mount

02The numbers

What These Numbers Mean

5 numbers in plain English · full specifications

Element countWell corrected

4 elements

This is what separates a good Barlow from the reputation Barlows have. A cheap two element design introduces its own colour error and softens the edge, which is why experienced observers used to warn against them. Four elements correct the aberrations the amplification would otherwise introduce, so the doubled image stays as sharp as the eyepiece alone was.

MagnificationThe useful factor

Two is the factor that pairs sensibly with a normal eyepiece set. It turns an 18 mm into an effective 9 mm and a 10 mm into a 5 mm, which fills the gaps most kits have. A 3x sounds better and in practice pushes past what the atmosphere supports on all but a handful of nights a year.

Eye relief effectThe hidden benefit

Preserved

This is the advantage people miss. A genuine 5 mm eyepiece has cramped eye relief, often five millimetres, which is unpleasant. Barlowing a 10 mm gives you 5 mm of magnification while keeping the 10 mm's comfortable eye relief, so you get the power without the eyelash-on-glass experience.

RetentionConsiderate

3 screws, compression ring

A single thumbscrew bearing directly on an eyepiece barrel leaves a dent, and over time a dented barrel sits crooked. A compression ring spreads the pressure around the whole circumference, holding the eyepiece square and leaving no mark. On a budget accessory this is a sign someone was paying attention.

Weight and lengthSubstantial

219 g, 59.5 mm

A Barlow adds its own length and mass to the focuser, and an eyepiece sits on top of that. On a small alt-azimuth mount the combination can be enough to shift the balance, and on a focuser with limited outward travel the added optical length occasionally means you cannot reach focus at all.

Optical

Magnification2x

Elements4

CoatingsFully multi-coated

Filter threadM28.5 x 0.6

Build

Barrel size1.25 inch

Barrel typeStraight, stainless steel

Insertion depth39.5 mm

Length59.5 mm

Weight219 g

Retention3 thumbscrews with compression ring

03Before you buy

Good to know.

The honest caveats — the things that save you a return, a bad first night, or a second purchase you didn't need.

Four elements is the specification that matters.

Barlows earned a poor reputation from cheap two element versions that visibly softened the image. A four element design is a different thing, and it is why this one is worth owning where a bargain Barlow is not.

It is a fair-weather accessory.

Doubling magnification also doubles how much atmospheric turbulence you see. On an average night the un-Barlowed view often shows more detail, and knowing when to leave it in the case is part of using one well.

Put your Moon filter on the Barlow.

The front filter thread means a neutral density filter can stay on the Barlow permanently rather than being unscrewed between eyepieces.

Check your focuser travel.

A Barlow moves the focus point outward. Most telescopes cope easily, but a Newtonian with limited inward travel occasionally will not reach focus with one fitted.

Editor’s Take

A Barlow is the highest leverage forty dollars in a beginner's kit and also the accessory most likely to be blamed unfairly. It gets blamed because doubling the magnification also doubles the visible effect of a turbulent atmosphere, and people conclude the glass is soft when the sky is. Buy a four element one, use it on the nights that deserve it, and it will effectively double the size of your eyepiece collection for the price of the cheapest eyepiece in it.

— The Skynocular verdict

80/ 100

SVBony SV216 2x Barlow Lens

2x Barlow · 4 elements · 1.25 inch · W9168A · $59.99

Doubles the magnification of any eyepiece you put in it, so a two-eyepiece kit behaves like a four-eyepiece one. Four elements rather than the usual two, which is why it holds up at high power.

SVBONYPartnerBest price$59.99→

SVBony SV216 2x Barlow Lens

Two eyepieces, four magnifications.

What the setup looks like.

Compatibility.

What These Numbers Mean

Good to know.

Related accessories.