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Explore Scientific 1.25" 3x Focal Extender / Barlow # FE03-125

4.9 (8 Reviews) Read Reviews Write Review
Brand Explore Scientific
Part Number FE03-125
Availability available

Product Info

Manufacturer Description

Increase Your Magnification Without Sacrificing Magnification Factor or Eye Relief

A Focal Extender does exactly what the name implies; it extends the effective focal length of the lens that it is used in conjunction with, thus producing higher magnifications for imaging and visual applications.

Focal extenders are similar to a Barlow or tele-negative lens, but there is one important difference between the two that you will want to take into consideration, especially if you plan to use the Explore Scientific Focal Extender for imaging and astro-photography.

When you use a standard Barlow or tele-negative lens to increase the magnification of your optical system, your results will be dependent on where you place the Barlow in the optical chain. For instance, if you put a 2x Barlow lens in front of your diagonal instead of behind it (Barlow-Diagonal-Eyepiece as opposed to Diagonal-Barlow-Eyepiece), you won't get 2x magnification in both set-ups. The magnification varies with placement. However, with an Explore Scientific Focal Extender, even if the distance is changed, the magnification remains the same. You can place your Focal Extender anywhere along the optical chain between an eyepiece or a camera, and if you are supposed to get 2x magnification, you will get 2x magnification.

When it comes to imaging, this is a critical difference, because you may want to introduce an accessory like a flip mirror or filter wheel in between the Focal Extender and a CCD camera, which would increase the distance to the focused image. This difference in design allows users to rest easy, whether they are pumping up the magnification of a lower power eyepiece for visual observations or using their Explore Focal Extender in imaging applications.

Explore Scientific Focal Extender Highlights

  • More Magnification Choices without Sacrificing Eye Relief: A good Focal Extender adds some real versatility to your telescope accessory line-up. First of all, it allows you to increase the magnification of any eyepiece with the same barrel size that you already own. In other words, 3 eyepieces offer 6 magnification choices with the addition of a focal extender. Secondly, most of the time, lower magnification eyepieces have better eye relief than higher power models. When using a focal extender to increase your magnification, you get to enjoy the generous eye relief of the lower power eyepiece, and that's quite a bonus, especially for eyeglass wearers or for those with fast telescopes who can really push high magnification eyepieces. Remember, we make focal extenders in 2X, 3X and 5x models, so there is something for every style of telescope.
  • Optimized Optical Design: Explore Focal Extenders are optimized through each design, fabrication, and testing process to produce high contrast, high resolution images.
  • Durable EMD Coatings & Finishing Touches: Each of the four elements in your Explore Scientific Focal Extender is fully multi-coated with EMD (Enhanced Multi-Layer Deposition) enhanced coatings, resulting in bright, sharp images. And like Explore Scientific eyepieces, the lenses are edge-blackened to eliminate internal light scatter. When you add a high quality focal extender to your optical chain, the entire optical package is optimized for the highest light transmission and contrast, and will deliver crisp, clean images to your eyepiece or imaging system.
  • Tapered Barrel for Extra Security: The insert barrel of each extender is double-tapered to allow smooth insertion to, and removal from, a telescope's eyepiece holder, focuser or diagonal, however the wide dimension of the taper helps prevent the focal extender from falling out of the telescope should the set-screw holding it in place become loose.


Producing optics for amateur astronomers that can be relied upon to deliver research-quality images requires a solid design, careful fabrication, multiple tests, and continued diligence to make sure we are always doing everything we can to produce a cutting edge, quality product. This is what we do at our facilities at Explore Scientific, and to insure your satisfaction, we back each eyepiece with the Explore STAR Transferrable, Extended Life of the Product Warranty, so you can keep exploring!

Key Specifications:

  • Total height = 3.80" / 96.5mm
  • Length of 1.25" nosepiece = 1.17" / 29.75mm
  • Weight = 8.6oz / 244g
  • Clear lens aperture = 0.47" / 11.9mm
  • Made in China

Reviews

4.9 (Based on 8 Reviews) 88% of reviewers recommended this product.
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    1. Guest

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      Review by Randy R.
      1547824212
      Jan 18, 2019

      5.0 A Must for Planetary Imaging with shorter focal lengths

      Pros:

      Cons:

      Comments:

      So much better for planetary imaging that a barlow. Why? You can place this anywhere in the optical train without complicating your required backfocus.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    2. Guest

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      Review by james k.
      1544393862
      Dec 9, 2018

      5.0 very nice, unexpected benefits!

      Pros:

      Cons:

      Comments:

      Many Barlows make excellent fields and contrast. This is in the best rank for that, but it adds no in-travel penalty(super), no eye-relief push(meh), and no field loss for long-FL eyepieces...that effect is fantastic. some EPs actually gained field! I suspect the full-span glass gives you that awesome benefit.. A Tri-Mag is 5oz, and this is 8oz...a bit heavier, but this is not a monster weight.. Very valuable for my fleet of salvaged Japanese all-glass aspherics...beautiful planetary views.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    3. Ronald Zincone

      Ronald Zincone New Member

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      Review by Ronnie Z.
      1508617433
      Oct 21, 2017

      5.0 Beautiful glass!

      Pros:

      Cons:

      Comments:

      Spectacular optics from Explore Scientific and sold by Agena AstroProducts!

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    4. Guest

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      Review by Derek of Westport, IN.
      1455062400
      Feb 9, 2016

      5.0 Great to have as a boost beyond your 2x barlow.

      Pros:

      Easy to Use,Quality Lenses,Strong Construction

      Cons:

      Comments:

      This helps to boost magnification during great seeing. I have also used it for planetary astrophotography.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    5. Guest

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      Review by they call me "Mr. Jim". of Little Rock, AR.
      1454630400
      Feb 4, 2016

      5.0 Excellent Focal Extender

      Pros:

      Strong Construction,Accurate,Quality Lenses,Easy to Use

      Cons:

      Comments:

      I bought this to help take my planetary imaging to the next level. So far I am very happy with it.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    6. dogstar

      dogstar New Member

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      Review by Starthrower of Southern New Hampshire.
      1424995200
      Feb 26, 2015

      5.0 Glad I stopped hesitating!

      Pros:

      Quality Lenses,Strong Construction,Easy to Use

      Cons:

      Comments:

      This is an excellent Barlow/Focal Extender. I have seen no evidence of optical artifacts in its use. I wasn't sure I really needed a 3x, but after using it (I have the ES 2x) I feel its a great addition to my optical kit. It is heavy, however, just like all ES products, so be sure the weight of this with an EP will be manageable on your scope.

      Bottom Line: Would you recommend this item? No
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    7. Guest

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      Review by Mike in the Mountains of Berkshires, MA.
      1409961600
      Sep 5, 2014

      4.0 Performs as Advertised!

      Pros:

      Quality Lenses,Easy to Use,Strong Construction,Lightweight

      Cons:

      Comments:

      Beautifully made and easy to add to any imaging train. This item makes placing the small planetary disks right on the center of the camera's sensor. Lightweight, too.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

    8. Guest

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      Review by Astrobug of Portland, OR.
      1365638400
      Apr 10, 2013

      5.0 Beats a Regular Barlow...For Less $$

      Pros:

      Easy to Use,Strong Construction,Quality Lenses

      Cons:

      Heavy

      Comments:

      In the few times I've used it, it puts my stable of regular Barlows (2" 2X GSO, 2.8x Klee, 3X Apogee, and 2X Orion Shorty Plus) to shame. None of the others perform acceptably with my 30mm Celestron Ultima (they all lengthen the eye relief, causing the apparent field of view to shrink noticeably, and the field stop becomes fuzzy). The ES 3X focal extender just disappears in use, as if whatever eyepiece you are using was magically placed into a longer focal length instrument; no adverse effects on eye relief, apparent field, or field stop sharpness whatsoever. No glare, ghost images, or scattered light were noticeable either.

      I primarily bought this to use with a DayStar H-alpha filter to achieve ~f/30, and it worked well here with my 80mm f/6.25 ED scope, even if it's a little less elegant than the 2" 4x Powermate that DayStar recommends.

      Fit & finish are superb, I am especially impressed by the lens coatings...it takes a bright light to even _see_ the glass surface, especially on the positive lens group that is nearest the eyepiece.

      The only cons I can see are the weight (about twice that of a typical 1.25" Barlow, but still manageable) and undercut (it's the ramp style, which I like better than the slot style, but I would prefer none at all). If there were a clever way to provide for a compact t-thread attachment like the Powermates, that would be nice for my specific solar application. But these are very minor quibbles.

      In short, ES has another winner here; performance closer to a Powermate at the price of a good 'standard' Barlow. I may have to get the 1.25" and/or 2" 2X versions. But first things first, my other Barlows are going up for sale!

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Specifications

      Manufacturer Explore Scientific