My first impression of the Barlow, after taking it out of the box, was that it felt like it could have come out of a Christmas cracker. It’s not heavy, lighter (barely 55 grams) in fact than its
I was pretty convinced for a while that this is constructed from a lightweight polymer rather than a form of alloy. I don’t know. Kryptonite perhaps? It is very shiny. I now think it is light cast aluminium.
SvBony’s marketing department claim:
“Cemented doublet and FMC film enhanced light transmission and achromatism; Unique matting ink around the glass lens decrease the stray light” (sic)
So I’m guessing the element edges have been blacked. The barrel is conventionally baffled, the element has no provision for a filter thread. From my measurements this ‘shorty’ Barlow is 75mm tall with a standard 22mm brass barrel. The element stands 16mm tall in its housing with at least 20mm of clear
Like its taller 3x sibling, the element is coated, although not obviously. I’ve read erroneous reports that these Barlows are uncoated. This is patently untrue as even a cursory glance reveals a pale green hint of optical coating. It’s probably fairly basic notwithstanding claims of ‘fully multi coated’. Although it doesn’t appear detrimental or affect its efficacy in use.
It features a brass compression ring and a plain brass screw. The screw isn’t the smoothest I’ve used but it held a Celestron zoom pretty securely. I certainly didn’t have any anxieties about it working loose. Many short Barlows have very small, almost undersized fastening screws.
I don’t always trust heavier eyepieces with these.
I directly compared the SV137 with a stock 2x