Plössl eyepieces are one of the most popular eyepieces among astronomy enthusiasts. They are inexpensive and have a relatively wide field of view (about 50 degrees). I received a Svbony SV131 eyepiece with a focal length of 32 mm and a mounting diameter of 1.25 inches for review. This is a four-lens eyepiece made according to the Plössl design.

Model Svbony SV131
Eyepiece Type Plossl Eyepiece
Focal length 32mm
Field of View 48 Degree
Exit Pupil 23mm
Eye Relief 19mm
Field Stop Diameter 25mm
Lens group 2 Group / 4PCS
Lens coating FMC
Side of the lenscoate Matt Blackened
Meterial Metal & Optic Glass
Thread size M28.5*0.6 for 1.25 inch filters
Eyecup type Rubber
Non-slip Cover Yes
Net Weight 116.5 g/4.11oz
Dimension Ø61X104mm

The eyepiece is supplied in a small package. The set includes an eyepiece and two protective covers. There is no damage or defects. The eyecup is rubber, folding, 2 positions, removable. The height of the unfolded eyecup is 12.4 mm.

Svbony MK105

Svbony MK105

At the end of October 2022, Svbony announced the release of a mirror-lens telescope of the Maksutov-Cassegrain system with an aperture of 105 mm. This was quite unexpected, since before that among Svbony telescopes there were only lens telescopes (refractors). And so, Svbony kindly provided me with a MK105 telescope for testing.

Svbony MK105

Svbony MK105

The meniscus optical system was invented by the Soviet scientist and optician Dmitry Dmitrievich Maksutov in 1941. In the Maksutov-Cassegrain system, the primary mirror is a spherical high-aperture mirror. Spherical aberration of the primary and secondary mirrors is compensated for with a full aperture lens corrector (meniscus) at the front of the tube. In this case, a convex spherical secondary mirror can be deposited directly on the meniscus, but then the relative aperture of the telescope should be in the range of 1:12–1:15 to eliminate spherical aberration as much as possible. For the first time I looked into the meniscus telescope around 2007 and since then I have fallen in love with the “poppies” for their compactness, the complete absence of chromatism, the absence of rays in the image and unpretentious maintenance. However, despite the apparent simplicity (all optical surfaces can be spherical!), increased requirements are imposed on the mechanics, mirrors, and especially the meniscus, otherwise the telescope will not be able to provide alignment stability and diffraction image quality.

I tested a 3x Barlow SVBONY SV213 lens with a 1.25″ barrel. The manufacturer claims a three-element optical design and blackening of the lens edges. Thanks to the three-lens design, the image quality across the field should be better than that of simple two-lens Barlows. At the same time, the SVBONY SV213 is not telecentric:
– magnification can be increased using an additional extender tube
– increases the eyepiece eye relief
– works worse with eyepieces (especially with wide-angle ) than a telecentric lens like Svbony SV216 2x.

SVBONY SV213 1.25

SVBONY SV213 1.25″ 3x Barlow lens


Model SV213
Barrel Size 1.25 inch
Magnification Factor 3X
Number of Lens Elements 3- Elements
Lens Coatings Fully multicoated
Outside Length of Upper Body 2.30inch / 58.5mm
Insertion Depth 1.02inch /26mm
Max Diameter Excluding Thumbscrew 1.57inch / 40mm
Net Weight 3.14oz / 93g
Filter Threads M28.5×0.6
Barrel Material Aluminum Alloy
Number of Thumbscrew 2PCS
Thumbscrew Thread Specification M4x8
Compression Band/Ring in Eyepiece Holder Yes


I received for test Barlow lens Svbony SV216. The Barlow lens is an optical accessory that allows you to increase the focal length of the telescope several times. It can be used both for visual observations and for astrophotography. The manufacturer claims consistent 2x magnification, fully multi-coated 4-element construction, blackened lens ends, a flat field of view, and a 1.25″ fit with M28.5 x 0.6 filter threads.

SVBONY SV216 1.25

SVBONY SV216 1.25″ 2x Barlow lens

However, constant magnification implies another important property – telecentricity, that is, this Barlow lens does not change the slope of the rays coming from the lens. The telecentric Barlow lens cannot be “overclocked” by an additional sleeve, does not increase eyepiece eye relief, introduces less distortion and works better with wide-angle eyepieces.


Model SV216
Barrel Size 1.25 inch
Magnification Factor 2x
Number of Lens Elements 4- Elements
Lens Coatings Fully multicoated
Outside Length of Upper Body 2.34inch / 59.5mm
Insertion Depth 1.55inch /39.5mm
Max Diameter Excluding Thumbscrew 1.73inch / 44mm
Net Weight 7.72oz / 219g
Filter Threads M28.5×0.6
Barrel Type Straight Barrel
Barrel Material Stainless Steel
Number of Thumbscrew 3PCS
Thumbscrew Thread Specification M3x10
Compression Band/Ring in Eyepiece Holder Yes