what is a barlow lens used for

what is a barlow lens used for

Superzoom pocketable cameras, lengthy telephoto lenses, binoculars, and telescopes are there to allow you to see up shut distant and/or small targets.

When you have a telescope, you recognize you may improve the magnification through the use of a brief focal eyepiece.

You're reading: what is a barlow lens used for

However what if you wish to get even nearer? Enters the Barlow lens.

Barlow lenses are an inexpensive strategy to improve the magnification of your setup, so, earlier than you run to your seller to purchase a bigger telescope, let’s see what a Barlow lens is and the way you utilize it.

Celestron barlow lenses
Celestron X-Cel LX 3X (left) and 2X (proper) Barlow lenses.

What Is A Barlow Lens?

Barlow lenses are optical components which might be named after Peter Barlow, an English mathematician and physicist who developed the primary prototypes for this sort of lenses again in 1833.

Trendy Barlow lenses are utilized in astronomy and astrophotography as optical components to extend the magnification of a telescope.

A Barlow works equally to a basic teleconverter, used to extend the efficient focal size of pictures lenses.

comparison between a teleconverter and a barlow lens
A comparability between a basic 2X teleconverter utilized in pictures (left) and a Barlow lens (proper) used with telescopes.

Teleconverters normally have extra glass than Barlow, however their discipline of view is usually higher corrected and in addition the main focus doesn’t change.

How Does A Barlow Lens Work?

A Barlow lens is a diverging lens that will increase the efficient focal size of the optical system.

A Barlow is rarely the final aspect within the optical practice and what it does is to increase additional outwards the cone of sunshine from the a part of the optical practice that’s earlier than it, in order that what comes after, sometimes the eyepiece or the digital camera sensor, will see a bigger picture.

effect a barlow lens has on telescope optics
Cone of sunshine behind a telescope (A) with out (purple) and with (inexperienced) a Barlow lens optical aspect (B).

Profit Of Utilizing One For Astrophotography

The apparent advantage of utilizing a Barlow lens in astronomy and astrophotography is that it’s an inexpensive strategy to enlarge the picture out of your telescope.

Copernicus Crater with 2x barlow zoom
The world round Copernicus Crater. Olympus OM-D EM-5 Mk ii in direct deal with Skywatcher Skymax 90/1250 with Celestron X-Cel LX 2X Barlow.

Significantly for those who do astrophotography in direct focus moderately than in eyepiece projection, i.e., you utilize the telescope as a photographic lens, a Barlow lens is a should.

On this case, you can not use the eyepiece of various focal lengths to be able to enlarge the picture.

The commonest Barlow lens affords a 2X, 3X, or 5X magnification. Some Barlows, referred to as variable Barlows, have an extended nosepiece: as for eyepieces, actually, by sliding in or out the Barlow you may alter its magnification.

Meade 2X-3X variable Barlow

Meade 2X-3X variable Barlow.

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One other profit is {that a} Barlow lens can assist you to realize focus along with your digital camera in case your telescope has a brief backfocus.

Due to the divergent lens within the Barlow, the upper the magnification it offers, the extra backfocus you’ve got. With an extended backfocus, you could possibly attain focus along with your digital camera.

Drawbacks Of Utilizing One For Astrophotography

Whenever you use a Barlow lens, you’ve got a few shortcomings to think about:

  • A Barlow lens makes the picture darker.
  • A Barlow lens magnifies your telescope achromatism and may introduce different optical aberration within the picture.
  • A Barlow lens will increase the optical decision of your setup and you’ll be simply oversampling your picture.
  • With a Barlow lens, due to the upper magnification and optical decision, you usually want a really exact Polar Alignment and/or a guiding system.

As a result of it’s a diverging lens, the cone of sunshine is unfold on a bigger space, so the picture will get dimmer with the rise of the magnification.

The identical is true for teleconverters used with photographic lenses: a 1.4x teleconverter causes a lack of brightness of 1 f-stop, whereas a 2X teleconverter darkens the picture by a full 2-stops.

If you have already got a gradual telescope, corresponding to a small Maksutov, utilizing a Barlow with excessive magnification can show difficult and, finally, unfit.

With my SkyWatcher Skymax 90/1250, a Barlow 3X pushes the instrument over its excellent limits. I discovered I can get higher outcomes through the use of a Barlow 2X after which crop.

Is A Barlow Lens Price It?

Regardless of the few shortcomings I discussed earlier than, a high quality Barlow lens is a terrific software, properly value having in your tools, however select it properly.

Televue Barlows are sometimes thought-about the very best Barlow lenses available on the market, however their value is sort of steep.

Televue 2x Barlow

The Televue Barlow Powermate 2X.

Celestron X-Cel LX 2X and 3X Multi-Coated Barlows have a extra inexpensive design, however they nonetheless provide an excellent picture high quality.

How To Use A Barlow Lens

Utilizing a Barlow lens is in no way troublesome.

Usually, a Barlow lens is made for use together with an eyepiece.

Celestron Barlow with the eyepiece installed
My Celestron Barlow with the eyepiece put in.

For remark, you merely insert the eyepiece within the Barlow and the nostril of the Barlow the place you’ll normally insert the eyepiece (the diagonal or the focuser).

showing how the barlow lens can be installed
For remark, the Barlow can go both within the focuser, as in my 130/650 SkyWatcher Flextube dobson (prime) or on the diagonal, as proven with my Mac (backside).

For pictures, you have to get a nosepiece on your digital camera. If you’re utilizing a planetary digital camera corresponding to a ZWO ASI 120 MC, the nosepiece is included. In the event you use a DSLR or mirrorless digital camera, you might want to purchase one on your T2 adapter.

using a T2-MFT adapter with a barlow lens
My T2-MFT adapter for my Olympus MFT cameras and the 1.25” nosepiece I exploit to attach the digital camera to a Barlow lens.

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Merely mount the T2 adaptor with the nosepiece in your digital camera and insert it within the Barlow. Then, insert the nosepiece of the Barlow behind the scope or within the focuser.

Olympus OMD connected with the Celestron X-Cel LX 3X Barlow
My Olympus OMD linked with the Celestron X-Cel LX 3X Barlow to the Skywatcher Skymax 90/1250.

Typical Functions For A Barlow Lens

Barlow are principally utilized in Planetary and Lunar astrophotography.

With planets since you need to get extra particulars on their floor, such because the bands in Jupiter, Mars ice caps, or the Cassini Division in Saturn’s ring system.

jupiter and saturn images with a 3x barlow
Jupiter (prime) and Saturn (backside). ZWO ASI 224 MC with Celestron X-Cel-LX 3X Barlow and SkyWatcher Skymax 90/1250 telescope.

With the Moon, Barlow lenses are nice to shut in on lunar floor particulars, corresponding to crater rims and central peaks, rimae, and mountain ranges.

Plato Crater using a OM-D and celestron barlow
The world round the well-known Plato Crater. Olympus OM-D EM-5 Mk ii in direct deal with Skywatcher Skymax 90/1250 with Celestron X-Cel LX 2X Barlow.

Barlow lenses don’t have any place in deep-sky astrophotography, as you need brighter pictures and excessive magnification, it requires an especially exact monitoring, guiding, and polar alignment.

On this case, as a substitute of a Barlow, you ought to use a focal reducer, an optical aspect that reduces the efficient focal size and the f-ratio of your telescope.

Distinction Between A Barlow Lens And A Zoom Lens

Each a Barlow and a Zoom change the efficient focal size of a telescope or of the lens.

The principle distinction between the 2 is that good high quality zoom lenses are rather more costly than good Barlows.

It’s because extra glass is utilized in zoom lenses than in Barlow, it’s harder to regulate optical aberration in a zoom than in a Barlow.

Barlow Lens Vs Small Digicam Sensor: Which Is Higher?

It’s identified {that a} cropped sensor digital camera produces bigger pictures than that of a full-frame one, offering the focal size is identical.

This impact is named crop issue and it’s not a real magnification, however it’s equal to crop down the full-frame picture.

A Barlow, as a substitute, does present a real magnification and an enchancment within the optical decision, at the price of darkening the picture.

In brief, small sensor planetary cameras and Barlow lenses are completely different, however usually complementary, devices to squeeze probably the most out out of your telescope for those who select them correctly.

A Video Recap

This video summarized very properly the idea and using the Barlow lens.


Barlow lenses are an awesome and inexpensive strategy to enlarge the picture out of your telescope, however you must select them rigorously.

A 2X Barlow lens might be the very best all-rounder, whereas Barlows providing larger magnification ought to be reserved for telescopes with giant aperture and comparatively quick f-ratio, because the picture dimmers with the magnification.

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