It multiplies the focal length, and the eye relief survives · review
A 2x Barlow with a four-element fully coated design in a 1.25 in barrel, published with its dimensions and weight.
The bottom line The most seriously specified Barlow here, and the longest and heaviest — which a small focuser will notice.
Most inexpensive Barlows use two. Four controls the aberrations that a doubled beam introduces at the edge of a wide field, which is what makes a Barlow usable with a wide-field eyepiece rather than only with a Plössl.
Eighty millimetres long, 31.8 mm across, 80 g. That length is worth noticing: a Barlow extends the distance from the focuser to the eyepiece, and a telescope with limited focuser travel may not reach focus with a long one fitted.
Doubling the focal length quadruples the exposure needed. The maker raises this, which is more than most Barlow listings do, and it is the arithmetic that decides whether a Barlow belongs in an imaging train at all.
“Fully coated” — one layer on each surface. With four elements there are more surfaces than in a two-element Barlow, so the label carries more weight here than it would elsewhere.
German, French and Italian Amazon stores ran from 31 € to 41 € on the day of the survey.
American and British Amazon stores list it in local currency, which the euro range above sets aside.
Spanish Amazon catalogue holds a record for it that nobody is selling.
Figures as Keepa reported them on the day this page was last updated. Stock and pricing shift without warning.
Prices quoted in this text were read on 17 September 2026. The live price is at the top of the page.
| Amplification factor | 2x — it doubles the telescope’s effective focal length |
|---|---|
| Element count | Four elements, fully coated per the maker |
| Barrel size | 1.25 in (31.7 mm) |
| Camera thread | Not published by the maker. |
| Effect on eye relief | Not published by the maker. |
| Coatings | Not published by the maker. |
| Body | 80 × 31.8 mm, as the maker publishes them |
| Weight | 80 g, as the maker publishes it |
| Amazon reference | DE B00462T81U · US B00462T81U · GB B005I7HT9A · FR B005I7HT9A · IT B005I7HT9A · ES B005I7HT9A |
| EAN | 4007922201078 |
A two-element Barlow corrects colour; a four-element design also controls the aberrations that show at the edge of a wide field. The cost is more air-to-glass surfaces, which is where the coating label becomes relevant.
Doubling the focal length at the same aperture quadruples the exposure needed for a given brightness. The maker mentions the effect; the arithmetic is the square of the factor.
0.5x focal reducer · 1.25 in · sold under the name “Barlow”
A 0.5x focal reducer in an anodised aluminium 1.25 in barrel, sold under the name “Barlow lens” while its own description correctly calls it a reducer.
Best for: Widening the field on a long-focal-length telescope, or shortening exposures on a camera
≈ €13
2x Barlow · achromatic · fully coated · metal body
A 2x achromatic Barlow lens in a full metal body, fully coated, described in four words per bullet.
Best for: Doubling the range of an existing eyepiece set at minimum cost
≈ £17 / €18
114 mm mirror · 900 mm focal length · alt-azimuth mount
A 114/900 Newtonian on a simple alt-azimuth mount, supplied with three eyepieces, a 6x30 finder and a 1.5x erecting lens, recommended by the maker from age eight.
Best for: A family telescope where nobody wants to learn polar alignment
≈ £150 / €142
