How To Use Barlow Lens - It's Working

I am a photographer, and I use the Barlow lens to get unique shots. Barlows are also helpful for doubling the power of your telescope eyepiece, which is great if you’re viewing objects too small or distant to see with an unaided eye. It’s easy-to-use, affordable (even free!), and it doesn’t take up much space in my bag. 

Barlow lens is a kind of optical device having two or more lenses that increase the focal length. That means it is used to improve the magnification of the telescope. 

The main objective of Barlow Lens is to increase effective magnification and decrease the field of view. It can be used as a low-power eyepiece, giving a low-power view and increasing the magnification as it will be stacked with another eyepiece.

In simple words, the Barlow lens is a kind of low-power eyepiece that can also be called a focal length extender.

It Is Always Better To Know How A Barlow Lens Works

The manufacturer provides the diagram of a telescope along with the Barlow lens wherein it can be seen that a Barlow lens is attached to the telescope.

The behavior of light is different when they fall on the lenses present in the eyepiece or Barlow lens. When light falls on an object, it comes back with the same path after bouncing from it, but when light falls on an eyepiece or Barlow lens, it does not come back with the same way; instead, after hitting the lenses, it is reflected in a different path.

Types IOf Barlow Lens

There are two types of Barlow lenses available

1) Negative(converging)

A Converging lens is a lens that causes parallel beams of light to converge together after being reflected or refracted from it. In contrast, a diverging lens is a kind of lens that causes the parallel rays of light to spread apart after being reflected or refracted from it.

2) Positive (diverting/Convex)

In other words, when light passes through a convex lens, it converges towards the lens and comes back with a focus after being reflected from an object. In contrast, when light passes through a concave lens, it diverges away from the lens and comes back with no focus after being reflected from an object.

Their behavior is quite the opposite of each other.

A Barlow lens is always used with another eyepiece for increasing the magnification of the telescope. When the Barlow lens is used with an eyepiece, it gives a low power view and increases the magnification as two of them are stacked together. It has some drawbacks, too, which are apparent if you compare its magnifying ability with a magnifying power of eyepiece alone.

Advantages Of Using Barlow Lens

-1) It increases the magnification of the telescope.

-2) Its eyepiece is lighter in weight and designed with a shorter focal length than standard eyepieces, making it easy to use with telescopes having lower load capacity.  In simple terms, we can say that its focal length is less than an eyepiece with a longer focal length.

-3) A Barlow lens can also be used to increase the magnification of a microscope, which is used in biological studies, ophthalmology, laser surgery, medicine and other fields.  It can also be used for terrestrial purposes like bird watching

Drawbacks Of Using Barlow Lens

-1) The field of view is decreased.

-2) It cannot be used as a high-power eyepiece.

-3) Chromatic aberration is produced.

-4) Some designs have low-quality coating, which becomes a big problem while observing planets and produce annoying flares.

Is Barlow Lens Worth It

As the Barlow lens is a kind of low-power eyepiece, so it increases the power by adding another low-power eyepiece resulting in increasing the magnification. It does not have good magnifying power compared with an eyepiece, but when used with different telescopes, this problem can be solved due to its versatility. But the Barlow lens cannot be compared with any other eyepiece in terms of its magnification.

Where Can I Buy A Barlow Lens

The Barlow lens is available everywhere, but if you are looking for some high-quality models, it is advisable to get them from reputed online stores like Amazon, eBay, etc. The price of a Barlow lens is also low, and you can buy them for a low cost.

The Barlow lenses have been used for a long time for increasing the magnification of telescopes, eyepieces, etc. Its demand is increasing day by day because it does not have any big drawback compared with other eyepieces available in the market. It is one of the low-budget accessories available for astronomers.

In a nutshell, we can say that it is worth purchasing a Barlow lens as its uses are not limited to telescopes but also for microscopes and other purposes related to light refraction.  

The designs of a Barlow lens vary from each other based on their usage. Some are designed for telescopes, while others are made based on microscopes etc. The quality of a Barlow lens depends on its magnification, focal length, etc.

If you are looking for some best brands, there are many options available in the market that you can choose from, but it is advisable to buy them from leading online stores like Amazon or eBay, where you can find a wide range of Barlow lenses

Difference Between Barlow Lens And Zoom Lens

The difference between a Barlow lens and a Zoom lens is that the Barlow lens works based on addition wherein an eyepiece with low magnification is added to another with high magnification resulting in increasing the magnification.

 In contrast, a Zoom lens works on replacement.  An example of this can be found when you use different lenses for photography with other embellishments. You can change your lenses without moving your camera position, which is impossible with a Barlow lens.

 The elaboration of the Zoom lens depends on its focal length while it increases the power due to addition in the case of the Barlow lens.

That’s all about the difference between a Barlow lens and a Zoom lens.


In short, we can say that the Zoom lens helps change the magnification of an image. In contrast, a Barlow lens helps increase the magnification of telescopes or microscopes without changing their position. The focal length and other features depend on the design, but many low-quality models are also available in the market that should be avoided.


Q: Isn't a Barlow lens just an empty tube or just a piece of plastic?

A: No, it is made of low-quality glass, and the designs of its lenses also vary from each other.  There are many high-quality models available in the market which you can choose from based on your requirements.

Q: What is the best Barlow lens available in the market?

A: It is difficult to say that many high-quality Barlow lenses are available, depending on your requirements.  Some Barlow lenses can be used for telescopes, microscopes, etc., while some cannot be used with these instruments. The prices also vary accordingly.

Q: How does a Barlow lens increase the magnification of telescopes?

A: It increases the magnification through addition, and this process can be done without changing any position.  That is why it is called a ‘Barlow.’ There are many different Barlow lenses available with low, medium, and high-quality designs. The quality of a Barlow lens depends on its focal length and magnification

Q: Do all eyepieces fit with a Barlow Lens?

A: No, the eyepieces of different types, such as Huygens, Ramsden, etc., do not match with any kind of Barlow lenses. Also, it is crucial to make sure that the lenses are in line with each other when using a Barlow lens.