GSO
GSO 2x ED Barlow 1.25-inch
2× · 1.25" · ED apochromatic
A sharp, colour-free 2× that doubles any eyepiece's power for a fraction of the premium price, the value pick for planetary and lunar detail.
85/ 100
Polaris Score
The value pick among the barlows we recommend
From$79.95
Where to buy
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01Will it fit my setup
Compatibility.
What this accessory works with — check the fit before you check the price.
1.25" focusersAny 1.25" eyepieceRefractorsNewtonians & DobsSCTs & Maks
Note✕Not for 2" eyepieces✕Adds one optical group
02The numbers
What These Numbers Mean
Magnification factorDoubles power
2x
It halves the effective focal length of whatever eyepiece you put in it, so a 20 mm becomes a 10 mm while keeping the 20 mm's longer eye relief. Two eyepieces plus a Barlow covers four magnifications.
Optical designLow colour
ED elements
ED glass in the Barlow keeps false colour and softness from creeping in at high power, which is where cheap Barlows earn their poor reputation. This is the difference between a Barlow you use and one that stays in the case.
Barrel sizeStandard
1.25 inch
Fits the standard focuser and diagonal size, so it works with essentially any telescope and any 1.25 inch eyepiece you already own.
Where it helps mostHigh power
Planets and doubles
Most useful on the Moon, planets and double stars, where magnification is the point. On faint deep-sky objects doubling the power also halves the surface brightness, so it usually makes them harder to see rather than easier.
Optical
TypeBarlow, ED doublet
Amplification2×
Fit1.25" barrel
GlassExtra-low-dispersion (ED)
CoatingsFully multi-coated
In use
BodyMetal, anodised
NosepieceStandard 1.25" filter threads
Best onMoon · planets · double stars
Pairs withMid- and long-focal eyepieces
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.
ED glass earns its keep at high power.
The extra-low-dispersion element is what keeps bright edges, a planet's limb, the Moon's terminator, free of the purple fringing cheaper Barlows add.
It won't beat your aperture.
Magnification is only useful up to what your telescope can resolve. Use the Barlow to fill gaps in your power range, not to push past a soft, dim ceiling.
Thread a filter onto the nose.
The nosepiece takes standard 1.25" filters, so a Moon or planetary filter can live on the Barlow and follow every eyepiece you pair with it.
04Completes the kit
Related accessories.
The natural partner
A comfortable mid-focal eyepiece
Pair with a 15–25 mm eyepiece for high power that still has easy eye relief.
Tame the glare
A Moon or planetary filter
Threads onto the Barlow's nose and stays put across every eyepiece you use with it.
Step up later
A premium 2× Barlow
If you upgrade to high-end eyepieces, a reference Barlow squeezes out the last bit of contrast.
85/ 100
GSO 2x ED Barlow 1.25-inch
2× · 1.25" · ED apochromatic · $79.95
A sharp, colour-free 2× that doubles any eyepiece's power for a fraction of the premium price, the value pick for planetary and lunar detail.