I have for sale a custom assembled 1.25? Barlow measured to 1.6x magnification factor. The lense is the 2x Williams optics binoviewer nosepiece Barlow. This is not the 1.6x Barlow that comes in their kit. This is the 2x lense that is bought separately. The lense is threaded into a blue fireball 1.25?-2? adapter. Finally, a standard 2?-1.25? adapter goes into the the 1.25?-2? adapter.
I measured the magnification factor repeatedly using Measurements of distance on a wall as viewed from 35 feet. The magnification came out to 1.62x for non-TV eyepieces and 1.57x for TV eyepieces.
The Barlow does require infocus room. With my 120ED there was only about 5mm of infocus left with the stock focuser. With the Moonlite focuser there is about 15-20mm of infocus left.
Performance of this Barlow is excellent. It is a flat field Barlow so it keeps the edges clean and slighted sharpens edge performance.
You can see in the photo the adapter has some flat black paint that ran onto the annodizing when I painted the threads.
Cost of Parts to make this was $ 90. Have this one for $55 shipped.