Barlow Lenses and Focal Extenders

Get the most out of your telescope with Barlow lenses and Focal Extenders

A Barlow lens or focal extender is the most efficient upgrade for any astronomer. Instead of spending a fortune on five different eyepieces, use this optical tool to instantly double or triple the magnification of your current set. At Telescoop.nl, you'll find only glassware that keeps your image sharp without sacrificing contrast or light output.

What exactly does a Barlow lens do?

Basically, a Barlow lens is an extra lens element that artificially lengthens the focal length of your telescope. It “fops” the telescope by making the beam of light slightly wider before it reaches the eyepiece.

• Magnification: A 2x Barlow effectively turns a 10mm eyepiece into a 5mm eyepiece. So you get the object twice as close.

• Viewing comfort: The big advantage is that you keep the eye relief (eye-relief) of your larger eyepiece. So you don't have to press your eye against the glass to still get that high magnification.

Barlow lens vs. Focal Extender

Although they are often confused, there is a technical difference in how they process light:

1. Standard Barlow lens: The magnification can vary slightly depending on the distance between the lens and the eyepiece. This is the standard for visual observation.

2. Focal Extender (Telecentric): This keeps the magnification exactly the same regardless of the position of the eyepiece. This is the absolute preferred astrophotography, because it provides a perfectly flat field of view without distortion at the edges of your picture.

What should you consider when choosing?

Not every magnifier fits every scope. To avoid disappointment, pay attention to three things:

• The Diameter: Check the size of your focuser or diagonal. Most telescopes use 1.25 inches accessories. For professional wide-field viewers, you often have the 2 inches variant needed.

• The Coating: Cheap glass creates internal reflections and a dull image. Our lenses feature high-quality multi-coatings (FMC) for maximum light transmission and high contrast.

• The Limit of Your Optics: More magnification is not always better. A small telescope with a 5x Barlow often results in a dark and blurred image. For most sets, a 2x or 3x Barlow the ‘sweet spot’ between detail and clarity.

Specialist advice

Calculating the ideal combination between your telescope, a Barlow and your camera or eyepiece requires precision. Looking for the perfect match for photographing Jupiter or simply want to see more detail on the Moon? Get in touch. We have the experience to give you the right advice right away.