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SvBony SV137 2x Barlow


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Nightspore

I was pretty taken with the SvBony SV137 3x Barlow, considering its competitive retail price. This made me wonder about the 2x version of the same bargain basement model. So, for a grand total of £19.99p I ordered one.

 

hrhgAnWl.jpg

 

My initial 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 total) in fact than its GSO equivalent, which is mostly made of aluminium. The SvBony has a chromed-brass barrel. The housing is very shiny, both outside and inside, which is not ideal.

 

3OSZ2qUl.jpg

 

I’m now pretty convinced that this is constructed from a lightweight polymer rather than a form of metal alloy. It may even be ‘kryptonite’ for all I know. It is very shiny. Probably not radioactive though.

 

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 aperture.

 

ZOVq6z3l.jpg

 

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.

 

H0Kjxgll.jpg

 

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.

 

m6YIWCll.jpg

 

I don’t always trust heavier eyepieces with these. The screws GSO use are very capable and have even been superseded by a bigger ‘chunkier’ version in the past few years or so. The SvBony at least equals the GSO in this respect. 

 

ObG4NwGl.jpg

 

I directly compared the  SV137 with a stock 2x GSO short Barlow that has only a slightly more expensive retail price. The GSO is basically a bog-standard two element Barlow. The comparison was on various double stars that could be viewed with my modified ST80 and a Celestron zoom giving magnifications between 33.3x and 100x. The seeing was below average. I honestly couldn’t see any discernible difference between the two Barlows. They both gave sharp, bright images without any excess false colour or aberrations that I could see (I expect a certain amount of natural CA with the ST80). The ‘Christmas cracker’ SvBony should be at least as good as the GSO on most targets. The element is fairly well constructed but the housing has its issues in my opinion. It isn’t internally blackened and is probably some type of plastic. Optically I could perceive no difference to the similarly priced GSO unit. However, the longevity or durability of a plastic housing would eventually concern me. 

 

M6cB7yml.jpg

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