GSO 1.25" 2.5x Apochromatic Barlow Lens # BL251
Brand | GSO |
Part Number | BL251 |
Availability | available |
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Product Info
Manufacturer Description
If you need more power than your eyepieces alone can provide, we offer a new apochromatic 2.5x Barlow lens from GSO (Guan Sheng Optical) to give a big magnification boost to any 1.25" eyepiece it's used with.
Nothing has been compromised in GSO's latest and finest offering. This Barlow features an air-spaced, three-element, apo design with fully multicoated optics. The housing is precision machined from aluminum stock and black anodized to a hard finish. The lens edges and inner barrel are blackened to provide maximum contrast. The Barlow body includes a brass compression ring so that your eyepiece barrels are not marred by the captive set screw. The 2.5x model has a clear aperture of 23mm. For those who need a very high quality Barlow for all-round use, the 2.5x barlow is a very nice step up from the typical 2x achromatic barlows commonly found on the market.
Specifications:
- Barrel size = 1.25" (31.7mm)
- Magnification factor = 2.5x
- Weight = 3.5oz (99gm)
- Total height = 2.95" (75mm)
- End caps = 2
- 1.25" filter threads on bottom of barlow: No
- Made in Taiwan
Reviews
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Feb 10, 2019
Excellent value!
Pros: Cons: Comments:I compared the GSO 2.5x apo barlow to a TeleVue 2x I had. First, this barlow functions as a 2.1x barlow, not a 2.5x. In any event, on Almach, the beautiful pair was easily separated in my 17mm Sterling Plossl and looked simply beautiful, orange primary and light blue secondary. But with the same eyepiece, the TV 2x barlow put up two dull, barely colorful stars. Maybe they were sharp, but dull and washed out doesn't cut it for colorful double stars. Sold the TV 2x and the GSO 2.5x apo barlow has a permanent spot in my eyepiece case now.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jan 18, 2017Good Barlow
Pros: Cons: Comments:I have compared this barlow with a 2.5X powermate and it compares very favorably. The powermate performs a little better but not enough to warrant the extra cost. I use it with my mak to get good planetary views with my plossl eyepieces.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
May 15, 2016Fantastic!
Pros:Accurate,Compact,Lightweight,Quality Lenses,Strong Construction,Easy to Use
Cons: Comments:Very easy to use and, when combined with a 10 mm eyepiece, the Barlow excels in fine focus. Best additional purchase to my new 6" Dobsonian.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 4, 2016How wonderful Barlow great optical quality
Pros:Quality Lenses,Lightweight,Accurate,Compact,Strong Construction,Easy to Use
Cons: Comments:This is a really great Barlow. I've had much more expensive models which are very good but I think this one is better optically and its more compact, lighter weight, so easier to use ....the screw is a little bit funky but it works very well and at least it has the brass band inside so it doesn't scratch up eyepieces.... I use this with my 58
Bottom Line: Would you recommend this item? NoThis review was provided courtesy of AgenaAstro.com
David Keller New Member
- Skill Level
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- Time with Product
- Unknown
- User Notes:
- Review by Dewi of Alexander, NC.
Mar 27, 2015Clear and sharp magnification
Pros:Lightweight,Compact,Quality Lenses
Cons: Comments:This GSO barlow is the best I have found for general use. I use Explore Scientific and TV eyepieces and this barlow magnifies without significant reduction of brightness or clarity. For the price you can't beat this barlow.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Mar 27, 2015Very Good Barlow
Pros:Lightweight,Easy to Use,Strong Construction,Accurate,Compact
Cons: Comments:I call this a very good barlow. If I could, would give it 4.5 stars for performance (but I rounded up, so it gets 5). Not perfect on all targets with all eyepieces but very satisfactory on nearly all. The ergonomics are very good, fit and finish excellent. No gripes for the price. Used in a 5.5" refractor.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Aug 17, 2014Good quality
Pros:Easy to Use,Quality Lenses,Lightweight
Cons: Comments:I use this on my refractor and my MAK. It has nice glass and pulls in the views. No need to pay more.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Aug 15, 2014Excellent Barlow!
Pros:Compact,Strong Construction,Quality Lenses
Cons: Comments:Excellent quality ... compared it to several more inexpensive Barlows (including an Omni 2x) and this one is the best and sharpest. Very happy and well worth the money!
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Rdamer726 New Member
- Skill Level
- Unknown
- Time with Product
- Unknown
- User Notes:
- Review by rd726 of Indiana.
Dec 6, 2013Nice
Pros:Easy to Use,Quality Lenses,Compact,Lightweight,Strong Construction
Cons: Comments:Nice shorter Barlow that works great. For most of my eyepieces it more along the lines of 2.2x than the listed 2.5x but that is what happens with most Barlows.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
dogstar New Member
- Skill Level
- Unknown
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- Unknown
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- Review by Starthrower of NH.
Jul 27, 2013Great quality, performance and price
Pros:Strong Construction,Easy to Use,Lightweight,Compact,Quality Lenses
Cons: Comments:This barlow offers a quite useful alternative to the 2x and 3x standards. Very nice build quality and so far great performance. I may have rated it five stars had I used it more, but so far on lunar work its seems to offer no apprecialble loss of clarity or color fidelity. Agena's delivery was breathtakingly fast, as usual, which is why I try to order from them whenever I can. In short, excellent product for the price, with fast delivery.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
May 30, 2013Great Barlow for the price
Pros:Quality Lenses,Strong Construction,Easy to Use
Cons: Comments:I use this a bit for visuals on planets, but where it's really helped is with planetary imaging. I use this in my 900mm focal length refractor and an imaging source planetary cam and have been really impressed with the images I've been able to get. I've shot Saturn with that set-up, and get clearly defined bands on the planet as well as a very clear Cassini division in the rings. Very happy with this barlow!
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Mar 22, 2013Good Barlow for the price
Pros: Cons: Comments:Nice Barlow, with good contrast at low to medium magnifications. The barrel is very well machined. In summary, very good value..
Bottom Line: Would you recommend this item? NoThis review was provided courtesy of AgenaAstro.com
Sep 21, 2012Great for planetary imaging
Pros:Quality Lenses,Compact,Accurate,Easy to Use,Lightweight,Strong Construction
Cons:Difficult To Focus
Comments:I use it for imaging planets with my C8 SCT and NexImage CCD. It gives a focal ratio of F/25, which I think is about the maximum that I am willing to go with that scope. The barlow looks like a quality item, and performs perfectly.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jun 26, 2012Better than Expected
Pros:Lightweight,Compact,Quality Lenses,Accurate,Easy to Use,Strong Construction
Cons: Comments:The seeing conditions on 6/23/2012 were great where I live, so I took my C8 out and aimed it at Saturn. I checked this Barlow out with every eyepiece I have and the results were fantastic. I even used it with my Televue 8 mm EP and the view of Saturn was still fantastic. I decided to aim at Arcturus and see if I could get an Airy disk, but seeing was not quite good enough to get a stable image. There is only one drawback. My Celestron 26 mm Plossl (made in Taiwan) wouldn't fit into this Barlow (also made in Taiwan) but my 32 mm Omcon Plossl (made in the same factory as the Celestron EP) did fit. Well...nothing is perfect, but this Barlow is a great deal, and great service from Agena.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 29, 2012Fantastic value!!
Pros:Quality Lenses,Easy to Use,Accurate,Strong Construction
Cons: Comments:I got this for my Astroscan. The rings of Saturn look fantastic. Great product,
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
spit New Member
- Skill Level
- Unknown
- Time with Product
- Unknown
- User Notes:
- Review by jonastro of Greensburg, PA.
Nov 4, 2011GSO 2.5X barlow
Pros:Strong Construction,Accurate,Easy to Use,Lightweight,Quality Lenses,Compact
Cons: Comments:I have a 2X antares APO barlow (celestron ultima clone)- I needed a bit more image size to image the planets, I had a 2.8X klee that worked great at the right EP power for visual, but was too much imaging and never gave a sharp focus, I was leary at 1st about this barlow and the price, but I ordered it anyway - agena shipped it immediately, upon arrival the barlow and coatings looked great!- I hear say the ultima is more a 2.2X ( though I cant say)- however the GSO does gives a larger image scale as a 2.5X would, what surprised me is- it has better color correction and is sharper than my antares- this barlow is truely a fantastic buy!- the only reason I gave it a 4 star is because it's not a powermate, don't take it the wrong way about the barlow, I'm so satisfied with the quality, I wont even consider spending over 3X the cost for the televue
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Oct 28, 2011Lens and design quality for a good price
Pros:Strong Construction,Quality Lenses
Cons:None
Comments:This item is a good complement to the 2" ED barlow when watching planets with a 2" crayford focuser. The strong construction allows to mount a digital camera.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Aug 20, 2011Can't Go Wrong Here
Pros:Compact,Easy to Use,Nice build and feel,Quality Lenses
Cons: Comments:I have an early Televue 2.5x barlow I use, and I wanted another less expensive 2.5x barlow for my young sons to use with their scopes (80mm f/5, 130mm f/5). This is a great barlow! We looked at M13 with the 130mm scope, and M57 with 80mm as test objects. Limiting magnitude for the unaided eye was 4.5 due to light pollution.
Bottom Line: Would you recommend this item? Yes
A Meade 13.8mm series 4000 eyepiece (early 90's, Japan) with a 68 degree apparent field was used on both objects. With the barlow this provided magnifications of 72x for the 80mm, and 117x for the 130mm scope.
No image degredation could be detected in either case. Both objects were sharp and clear with pinpoint stars. The barlow did its job of increasing power enough to render a more pleasing size to the objects with out any noticable loss of sharpness at all.
I would say it performs as well as my old Televue, at less than half the cost.This review was provided courtesy of AgenaAstro.com
Jun 26, 2011Compares to more expensive Barlows!!
Pros:Compact,Accurate,Easy to Use,Does its job well,Excellent multi-coatings,Quality Lenses,Strong Construction
Cons:None period
Comments:I believe you may well come up empty-handed (as I did) trying to catch this Barlow in the act of betraying its presence in the optical train - apparently no matter how good the rest of it may be. My home-built 6", f10.75 Newt uses a 1/21rst-wave primary and a Zygo-tested, 3/4" flat rated at about 1/22 of a wave and, having already rounded up the remaing usual suspects (thermal, stray light control, vibrations, collimation, etc), I was at least prepared to be let down by the GSO stuff. After all, their prices were so low compared to the big boys it almost seemed laughable to expect a lot. But, I still bit because these were the only Barlows I saw on the web that folks were actually raving about. Man, I'm happy I did. These GSO Barlows are for real (also have the 3x ED). But, I find that unless you have downright excellent seeing conditions (and, for me, that means for planetary viewing) you can have some trouble reliably attributing the viewing differences to either all the on-going Barlow-vs-eyepiece comparisons your making or to the variabilities of the seeing conditions. But, before sunset, for me, can be a great time as the seeing typically steadies quite well for some terrestrial viewing of targets of only a half-mile to a mile away. When it's steady enough and at powers of very roughly between 200x to 300x (on my 6"), it's like being there - razor sharp, bright, contrasty views that are better than any photograph. I've compared Tele Vue, Explore Scientific and Brandon eyepieces alone to their longer-focal-length stablemates paired with the GSO Barlows at equivalent magnification. Results were all the same: couldn't tell any difference with my GSO Barlows or without(!)
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jun 13, 2011Double your View
Pros:Accurate,Good price value,Compact,Quality Lenses
Cons:None at this stage
Comments:Great little Barlow used with Vixen SF80 and Celestron C6, very happy, highly recommended, good value for money.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 21, 2011I would buy and recommend this product
Pros:Strong Construction,Very well made,Quality Lenses,Compact
Cons:None
Comments:I use this primarily for Astronomy, mainly looking at the Moon with a 10mm and 15mm eyepiece. Barlow is well made and great care has gone into providing a quality product. The views I get while using the barlow are much better than an older barlow...I used to use!
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jan 5, 2011Best barlow for the money.
Pros:Accurate,Compact,Strong Construction,Quality Lenses
Cons:Short Tube
Comments:I bought this in combination with two EWA (UWA) Agena 15mm and 9mm EP. Before I had no barlow and only celestron 25mm and 10mm EP. WOW. The difference is incredible. All the new equipment feels very durable, and well made. It further proves that with how well I am able to see Jupiter (when weather permits ATM). I wish I would have got the set to save some cash, which is nearly the amount of one of the EP's.
Bottom Line: Would you recommend this item? Yes
Only thing I've noticed is the shorter tube for the barlow. I tried added two filters on my 9mm EP and I hit bottom before the EP section could go down far enough for the compression ring to hold it properly. Not too big of an issue though. I can always add them to the bottom of the barlow instead.This review was provided courtesy of AgenaAstro.com
Dec 26, 2010I would buy this product again
Pros:Compact,Quality Lenses,Strong Construction,Accurate
Cons:No cons so far
Comments:Used this product for astro photos and the results equal my Televue
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Apr 30, 2010Fantastic!
Pros:Compact,Quality Lenses,Accurate,Strong Construction
Cons:None
Comments:This does not have quite the clear aperture of the famous Celestron Apochromatic 2X Barlow, but at 2.5X, it really can't, and I needed that extra 0.5X with my short focal length scope. Truly a great find - you won't be disappointed with this.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Aug 6, 2009Quality at an affordable price
Pros:Strong Construction,Compact,Accurate,Quality Lenses
Cons: Comments:Using for planetary photos and general observing. Built like a tank! Nice looking.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
Jan 2, 2009Excellent barlow, inexpensive price.
Pros:Quality Lenses,Accurate,Brass clamping ring,Apochromatic,Fully multi-coated,Strong Construction
Cons: Comments:I ordered this GSO barlow lens to replace the dime-store plastic barlow lens that came as part of a telescope kit I obtained elsewhere. When the package from Agena arrived, the product exceeded my expectations. The all metal construction is top notch. The fit and finish on this barlow lens gives you the impression that it would cost at least twice as much as it does. It is far better constructed than a lot of my DSLR camera lenses that cost 3 to 5 times as much. The improvement over the original barlow lens is apparent at first use. The barlow does not significantly impact the visual quality of the eyepieces used. This is in sharp contrast to the original barlow which degraded even my 30mm eyepiece. This barlow removes one poor link in the optical train. One thing I noticed immediately was that this barlow lens appeared to make my plossl eyepieces parafocal. With this barlow attached, I don't need to refocus when changing eyepieces. That was an expected plus. If the quality of this barlow is any indication of the quality of the GSO line of optics and telescope parts, I will definitely be purchasing more from them. Agena Astro products was extremely easy to do business with. I will definitely do business with Agena again.
Bottom Line: Would you recommend this item? YesThis review was provided courtesy of AgenaAstro.com
AstroGuy1 New Member
- Skill Level
- Unknown
- Time with Product
- Unknown
- User Notes:
- Review by Stargazer of Michigan.
Nov 18, 2008Excellent compact barlow
Pros:Short and Lightweight,Excellent Views,Well machined,Excellent price
Cons:None
Comments:I picked up the GSO 2.5x Apo Barlow because I was unhappy with the performance of "another" brand that I had been using. Granted, the other brand was a bit lower in price but the difference in quality, in my opinion, was well worth the few extra dollars. The GSO Apo is a real bargain.
Bottom Line: Would you recommend this item? Yes
The barlow is well machined, short (3" overall), and light weight. Just handling it gives the feeling of a nicely crafted item. The undercut on the lower barrel is "just right". There's nothing that I hate worse (well, almost nothing) than an eyepiece, barlow, or any accessory getting hung up on the undercut because they're cut too deep. I usually end up with the set screw backing all the way out and falling in the grass. Then I'm crawling around in the dark...looking down instead of up!
The views using the GSO apo barlow are excellent. Nice wide, clear aperture of 23mm and the barlow becomes invisible in use. That is, you don't even know that there's more glass between the eyepiece and the scope.
I look forward to more clear nights and a chance to enjoy the barlow even more.This review was provided courtesy of AgenaAstro.com
May 10, 2008Excellent compact barlow
Pros:Well machined; Short and Lightweight; Excellent views; Excellent price
Cons:None
Comments:I picked up the GSO 2.5x Apo Barlow because I was unhappy with the performance of "another" brand that I had been using. Granted, the other brand was a bit lower in price but the difference in quality, in my opinion, was well worth the few extra dollars. The GSO Apo is a real bargain.
Bottom Line: Would you recommend this item? Yes
The barlow is well machined, short (3" overall), and light weight. Just handling it gives the feeling of a nicely crafted item. The undercut on the lower barrel is "just right". There's nothing that I hate worse (well, almost nothing) than an eyepiece, barlow, or any accessory getting hung up on the undercut because they're cut too deep. I usually end up with the set screw backing all the way out and falling in the grass. Then I'm crawling around in the dark...looking down instead of up!
The views using the GSO apo barlow are excellent. Nice wide, clear aperture of 23mm and the barlow becomes invisible in use. That is, you don't even know that there's more glass between the eyepiece and the scope.
I look forward to more clear nights and a chance to enjoy the barlow even more.Sort bySpecifications
Manufacturer GSO