I received an SV152 20mm 70 Degree SWA Illuminated Eyepiece (SKU: W9115A) for testing.
The manufacturer positions this eyepiece for the following applications:
-setting the exact alignment of the telescope and finder
-polar alignment (by drift method)
–an invaluable aid to centering guide stars and astrophotography target objects
-the perfect eyepiece for alignment of computerized GoTo systems
Field of view 70 degrees
Focal length 20 mm
Eye relief 16 мм
Crosshair – laser engraved
Lens group – 4 Group / 5PCS
Power – 2PCS 1.5V (AG5)
Lens Coated – FMC .
Field Stop – 25 mm
Thread – M28.5*0.6
Net Weight – 221g/ 7.8oz
Dimension – 75*53*102 mm
Field of view 70 degrees
Eye relief – about 16 mm
Ocular lens diameter – 26 mm (flat), 2.5 mm deepened relative to the body.
Field Stop – 25 mm
Package weight – 318 grams
Eyepiece weight with caps (without illumination) 197.5 grams
With illumination module – 220 grams.
Eyepiece length (with caps) – 85 mm
Eyepiece diameter – 53.5 mm
Eyepiece width (with illumination module) – 102 mm
Eyepiece skirt diameter – 31.8 mm
Filter thread diameter – 28 mm.
Eyepiece scheme – possible Erfle.
The eyepiece is delivered in a dense cardboard box. Inside the box there is an eyepiece, two protective covers, a plug in the side, a illumination module, batteries and a cleaning cloth. Everything is packed neatly in bags, no damage or defects.
The eyepiece body is completely metal anodized, except for protective caps and ribbed rubber strip. The illumination module is also made of metal.
The eyepiece skirt is made with a groove and thread for a filter. I tried to install the eyepiece in several telescopes and zenith mirror (Sky-Watcher BKP150750, Sky-Watcher Mak 90, Sky-Watcher 1.25″ diagonal mirror, 50 mm finder-guider) – the eyepiece was installed without friction or jamming, with a small margin. Filters 1.25″ wrapped around a skirt flawlessly. The eyepiece is blackened inside.
It is also possible to adjust the eyepiece for vision (by rotating the body). Refocusing is smooth, without jamming. The correction range is approximately -2 to +4 diopters.
The eyecup is soft rubber, you can roll it up or take it off. The eye relief is insufficient for observation with glasses even with the eyecup removed – another 3-4 mm is missing. The eyepiece can also be used with glasses, but then the edges of the field of view will not be visible, but the crosshair itself is visible with a large margin. For an observer without glasses, the eye relief is comfortable. It is necessary to accurately center the eye, otherwise additional aberrations will appear.
All lenses are coated. The color of coating is green, blue, lilac.
The glass plate with the crosshair is coated only from the inside (green flare), from the side of the skirt a bright colorless flare is visible. Considering that the outer side of the plate requires periodic cleaning from dust, I think this decision is justified.
The light source is a red LED. There were no problems with the assembly, everything is quite obvious – the illumination module spins up, two batteries are installed in it. Then you need to remove the rubber plug from the side of the eyepiece and screw in the illumination module. Turning the knob clockwise clicks and turns on the backlight. The brightness adjustment range is large. The crosshair is thin. The angular size of the crosshair is about 40 degrees. The plate with the crosshair is not removable, it is located just at the level of the backlight module.
Initially, the eyepiece was clean from the inside, however, during using, dust particles began to appear in the field of view (obviously from the side of the eyepiece skirt). To remove dust particles, I recommend using a clean microfiber cloth (for glasses) + an ear stick. The eyepiece skirt can be unscrewed for easier cleaning. Looking through the eyepiece at a light bulb or a light screen, I carefully removed all the dust. I do not recommend the complete cloth for cleaning the crosshairs or optics, as a lot of fluff has spilled out of it – only for cleaning the body. To prevent new dust from appearing on the plate, I recommend screwing a filter SVBONY 1.25” UV/IR Cut into the eyepiece skirt.
The SVBONY SV152 eyepiece can be used directly with the guide finder SVBONY SV106 – you will get an excellent illuminated finder..
When I tested with a 50 mm guider-finder (focal length 190 mm, f\3.8) and a Jupiter-37A photolens (focal length 135 mm, f\3.5) the eyepiece showed good image quality in about 60% of the field of view, then the image gradually degrades ( field curvature and lateral chromatic aberration). There is a slight pincushion distortion. The edge of the FOV is sharp with a thin blue border. When you stop the lens or use less fast optics (f\10), the image quality improves slightly.
+ excellent mechanical and optical workmanship
+ large field of view as declared
+ wide range of backlight brightness adjustment
– insufficient eye relief for observation with glasses
– noticeable degradation in sharpness at the edge of the field of view
Despite the disadvantages, the SVBONY SV152 eyepiece is an excellent solution for making finder with illumination (factory or homemade), or for other tasks (for example, polar alignment by drift method).