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. The short barrel also ensures that it sits fairly low in a 1.25" diagonal. In my experience these sort of Barlows/amplifiers usually achieve focus in short tube refractors without the need for extension tubes.
It probably contains four elements as there are very similar looking four element amplifiers on the market with a variety of brand names. I believe this particular tele-extender is very probably built by Jinghua Optics & Electronics Co., Ltd (JOC) in Guangdong, China. It seems to have good coatings and features a compression ring. There are also filter threads, a satisfyingly ergonomic rubber grip on the internally flocked housing, and a barrel undercut. I’m not a great fan of undercuts but this one has not been problematic in use.
The barrel itself appears to be chromed-brass and the entire unit has a quality feel to it. An 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 unit on a pleasant April night while 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 achromatic grab and go set-up. The ‘Omegon’ Amici was a last second decision because I could actually physically see the Moon from my vantage point. 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 smaller binary companion could be distinctly and clearly observed nestling in the first diffraction ring.
I tried a few small open clusters like
