Description
The BRESSER 5x Barlow Lens is a premium optical accessory with a standard mounting diameter of 1.25" (31.7 mm), which increases the effective focal length of the telescope and the magnification of the eyepiece by five times. Unlike the simpler 2x model, it uses a three-element air-dispersed scheme with ED glass and full multi-layer illumination, which provides a clear image with minimal chromatic aberration across the entire field. The Barlow is installed between the telescope and the eyepiece and allows for very high magnification, while maintaining a convenient large eyepiece and comfortable pupil distance of the long-focus eyepiece. Due to its high magnification, the accessory is primarily intended for large-aperture long-focus telescopes and digital photography (webcam, CCD), where it works as a focus extender. The brass clamping ring securely and without distortion fixes the eyepiece or camera. The optics are equally suitable for visual observations of bright objects — the Moon, the Sun with a filter and bright planets — and for astrophotography. It is important to consider: by increasing the focal length five times, the Barlow simultaneously reduces the brightness of the image five times and lengthens the shutter speed when shooting. Therefore, with short-focus glasses and on small telescopes, the picture becomes dark and soft — for them, Barlows with a lower multiplicity are more appropriate.
How it works (multiplication effect on your glasses)
A 5x Barlow lens increases the magnification of any eyepiece by a factor of five — or, what is the same, reduces its effective focal length by a factor of five:
40 mm eyepiece → works as 8 mm
20 mm eyepiece → works as 4 mm
15 mm eyepiece → works as 3 mm
10 mm eyepiece → works as 2 mm
Due to the high magnification of 5x, it easily exceeds the useful magnification of the telescope (approximately twice the diameter of the objective lens in millimeters). References to our telescopes:
8" Messier NT-203/1000 (ceiling ~400x): 20 mm eyepiece gives 250x, 15 mm - 333x (within the useful range) - the optimal combination.
12" Messier Dobson (ceiling ~610x): 20 mm eyepiece gives 381x, 15 mm - 508x - also within limits.
90mm Taurus (ceiling ~180x): 20mm eyepiece gives 225x already — beyond the useful limit; on this and smaller telescopes, 5x is impractical.
Design features
- 5x magnification - the lens increases the magnification of any eyepiece fivefold. This allows you to achieve very high magnifications that are not available with a regular set of eyepieces. Designed for long-focus large-aperture telescopes and digital photography. The user receives the ultimate magnification for detailing planets and the Moon under excellent conditions.
- Three-element air-gap design with ED glass - optics with three lenses with air gaps and special ED glass (Extra-low Dispersion). This design significantly reduces chromatic aberration, which would otherwise increase at high magnifications. The image remains sharp and color-neutral throughout the field. The user receives noticeably higher quality than from simple two-lens Barlows.
- Full multi-layered coating - all lens surfaces are multi-layered. They minimize light loss and ghosting, which is especially important at high magnification, when the image is already darker. Contrast and brightness increase compared to uncoated optics. The user receives the brightest and cleanest image for this magnification.
- Brass clamping ring - the eyepiece or camera is fixed with a brass clamping ring around the circumference, rather than with a single clamping screw. Brass does not scratch the eyepiece's mounting surface and holds it coaxially, without skewing. This increases the accuracy of installation and maintains the alignment of the optical path. The user gets a reliable and accurate fixation of expensive glasses.
- Dual purpose: visual and photo - Barlow is equally suitable for observation...
