SvBony SV137 2x Barlow

[Zeta Reticulan]

I was pretty impressed with the SvBony 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.

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 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.

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 aperture.

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 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, which possibly explains its competitive retail price. Optically I could perceive no difference to the similarly priced GSO unit. 

[Zermelo]

Thanks for this, @Zeta Reticulan.  I've been asking questions about Barlows elsewhere, so I was interested to see your thoughts on these two. Did you notice anything in particular about scattered light, especially on the brighter doubles?

btw, I see you have been posting a few equiment reviews recently. Is there any reason you haven't put them all in the dedicated section for member reviews?

[Mr Spock]

Defeats the cost object but solves the shiny inside - fit the nose piece to one of these:

They come in two lengths , 56mm and 70mm.
I have my Meade 140 Apo nose piece fitted to a 70mm to give x2.11 (measured).

 

[Mr Spock]

36 minutes ago, Zermelo said:

btw, I see you have been posting a few equiment reviews recently. Is there any reason you haven't put them all in the dedicated section for member reviews?

As they aren't asking for help or advice, I've moved them to the correct section.

[Zeta Reticulan]

2 hours ago, Zermelo said:

Thanks for this, @Zeta Reticulan.  I've been asking questions about Barlows elsewhere, so I was interested to see your thoughts on these two. Did you notice anything in particular about scattered light, especially on the brighter doubles?

btw, I see you have been posting a few equiment reviews recently. Is there any reason you haven't put them all in the dedicated section for member reviews?

You're welcome. To be honest, I couldn't detect any scatter with the SvBony, particularly compared to the GSO. I'm not saying it isn't there. I just didn't see it in my tests. 

SvBony also have a T-thread version. As far as I can tell the element is identical.

But definitely blackened inside. It is about £10 more though. 

In my opinion, this BST is one of the best shorties on the market. I paid over 80 quid for mine years ago because it has 'Omegon' written on it. At the time I had no idea it was originally Barsta. I have the 3x version as well. Although it doesn't say Omegon on it lol.

I find that I can often use longer Barlows in diagonals. If the size of the eyepiece used isn't too large or heavy it shouldn't be too detrimental to balance.

The TV 2x works well. I often use it with a 19mm Panoptic in a a short 60mm doublet. There is no vignetting at all, which can happen sometimes with wide angle EP combination in shorties. The Vixen DeLuxe 2x is similar. Although it's primarily designed for short focal length scopes. It also has no compression ring.

I must have originally posted this in the wrong section. My brain isn't always totally on the ball these days. I've literally had brain damage (stroke). I'm lucky if I know what day it is lol.

[Zeta Reticulan]

2 hours ago, Mr Spock said:

As they aren't asking for help or advice, I've moved them to the correct section.

Cheers. I knew I'd posted it in the wrong section. I just didn't realise that I knew that I knew. 

[Zeta Reticulan]

2 hours ago, Mr Spock said:

Defeats the cost object but solves the shiny inside - fit the nose piece to one of these:

They come in two lengths , 56mm and 70mm.
I have my Meade 140 Apo nose piece fitted to a 70mm to give x2.11 (measured).

 

This should work, providing the barrel length is 22mm. Otherwise the magnification will be over 2x.

[Zeta Reticulan]

Nice edit, Spock.