The 1.25“ Altair Lightwave 3x Flat Field Tele Extender Barlow weighs in at 195 grams and I make it 105mm tall. One of the reasons (if not the predominant one) I acquired this Barlow/amplifier was that its barrel is only 35mm leaving the remaining 70mm for the housing. This makes deployment in a 2“ diagonal (with an adapter) a lot safer as it helps ensure that the end of the unit doesn’t make contact with the mirror or prism surface. In my experience these sort of Barlows/amplifiers usually achieve focus in short tube refractors without the need for extension tubes.



It probably has four elements as there are very similar looking four element ‘Extender Barlows’ on the market with a variety of brand names. It seems to have good coatings and features a compression ring, filter thread, a rubber grip on the internally flocked housing, and a barrel undercut. I’m not a great fan of undercuts but this one hasn’t been problematic in use.



The barrel itself appears to be chromed-brass and the entire unit has a quality feel to it. The advantage of these ‘telecentric’ designs is that they don’t increase eye relief in use, unlike conventional Barlow lenses.



I got first light with the Tele Extender on the 14th of April observing a rapidly setting crescent Moon. I was using a modified ST80 and a Celestron Zoom inserted into an Amici prism. There were stacked Baader Fringe Killer and Neodymium filters threaded into the diagonal nose. The ST80 is my lightest grab and go set-up and the ‘Omegon’ Amici was a last second decision because I could actually see the Moon. I initially assumed it would be too low to observe.



The first thing that struck me was how sharp and defined the image was. I could detect no vignetting and considering how small the lunar phase was there was a wealth of detail. As the Moon got lower I switched the entire ensemble to a 2“ dielectric, discarded the Fringe Killer/Neodymium, and proceeded to observe several double stars. The seeing was a bit better than previous nights and splitting Epsilon and Delta Boötes at 100x were the first targets. I found I could easily push to 150x with ε Boo and the small green binary companion could be distinctly and clearly observed nestling in the first diffraction ring.



I tried a few small open clusters like NGC 1502 (Jolly Roger) and the M3 globular cluster at magnifications ranging between 50x and around 100x. I saw no aberrations in the field, apart from those attributable to an inexpensive achromatic doublet like the ST80. I’ve since used it with my Altair 60mm EDF and an 8~24mm zoom. Where it gives me magnifications between 45x to 135x. I can see this ‘Barlow’ getting a lot of use. It was well worth the £85 I paid for it.