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SvBony F9125A Barlow Element


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SVBONY 1.25'' 2X Barlow Lens Telescope M28.5*0.6 Thread for Standard Monocular Optics Compact Eyepiece 31.7mm SvBony (sic)




I thought I was being pretty clever using a stand-alone 2x SvBony Barlow element to decrease the focal length of my 6mm Vixen SLV. The element itself was threaded from off my rather shiny silver coloured SvBony 2x Barlow housing.




Imagine my surprise when I discovered that SvBony actually market separate individual 2x Barlow elements. I thought £13.99 was reasonable and duly acquired one.



It was delivered with its own plastic carrying container. My first impression was that it was quite lightweight compared to the SvBony element that I’d initially separated from its respective housing. The stand-alone element was well baffled and I was pleased to discover that its filter threads were compatible with everything I threaded into it. The lens surface at the field lens interface shows a strong curvature. This made me wonder if the element actually would magnify by 2x when threaded directly into an eyepiece barrel. It doesn’t, as I suspected. It is definitely coated though as you get a hint of a green surface sheen when the glass is held up to a light source. SvBony claim it has a ‘broadband’ coating.




After several daylight comparison tests I’d estimate it gives about 1.5x when threaded directly into an eyepiece barrel. However, it will also thread directly into most Barlow housings where it will probably increase the magnification to around 2x. This element is shown below threaded into an old 'Celestron' T-thread Barlow originally from a kit. These generic T-thread Barlows have been on the market for a long time and more recent versions feature aluminium barrels (often with an undercut) rather than the 22mm chromed-brass one on mine. They are also marketed by Sky-Watcher, Vixen, and even SvBony. I believe they were originally manufactured by Barsta (BST).




The actual magnification will depend on the barrel length (potential distance from the field lens).




I have a feeling that most standard 22mm Barlow barrels would give a 2x magnification. However, this would be slightly greater in the 30mm barrel typically used in many GSO Barlows (above left). When threaded directly into a 6mm Vixen SLV the F9125A delivers a bright image and appears to have excellent transmission. I saw no degradation in colour separation or acuity (at an assumed 90x) when viewing several double stars and the planetary targets Saturn and Jupiter.




1, Brand: SVBONY
2, Barrel Size: 1.25" (31.7mm)
3, Magnification Factor: 2X
4, Lens material: pure optical glass lens
5, Sleeve material: Metal
6, Lens coating: Broadband coating
7, Thread interface: M28.5*0.6 pitch (Fine Thread)
8, Weight: 12g
9, Total Height: 22mm


(SvBony’s webpage)


Edited by Nightspore
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Even with a low supermoon this Barlow element is still delivering. In less than perfect conditions I split Mu Bootis and Iota Cass at just under 100x with the Altair 60 EDF.




I'm pretty sure I could see Rhea (mag 10.1) as well as Titan. I'm still impressed with this element. 

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