The zoom eyepiece is a variable focal length eyepiece that allows you to quickly change the magnification by simply rotating the special ring on the body. In fact, “zoom” can replace several eyepieces, and at the same time, you can easily find the optimal magnification for various objects. Zoom eyepieces are also very convenient for mass telescope observations (“sidewalk observations”), where changing the eyepiece takes a lot of time. A few years ago, I was able to observe the planets in a unique short-focus zoom eyepiece Nagler 3-6 mm – I really liked it for the convenience of choosing the best magnification, as well as its small size. About a year and a half ago, Svbony sent me the SVBONY SV171 Zoom Eyepiece 8mm-24mm for review, and after testing, I suggested that Svbony consider developing a planetary zoom eyepiece.
Svbony company has kindly provided me with several eyepieces for testing. One of them – SV190 18mm 1.25″ Ultra Flat Field Eyepiece FMC. A flat field (no curvature), a large eye relief (20 mm) and a field of view of 65 degrees are declared. Interesting!
The focal length of 18 mm is one of my favorites, as it is especially in demand with “fast” telescopes (f\5…f\6) when observing deep space objects (galaxies, nebulae, clusters). With “slow” telescopes (f\8…f\12), the eyepiece can be used for observing the Moon and bright compact objects in deep space.
I received an SVBONY SV171 Zoom Eyepiece 8mm-24mm (SKU: W9131A). for testing. The zoom eyepiece is very convenient for quickly selecting the optimal magnification, or for cases when you need to quickly change the magnification without having to change eyepieces. The focal length in the zoom eyepiece is changed by rotating the body. Along with the focal length, the angular field of view of the eyepiece also changes.
|Focal Length||8-24 mm|
|Eye Relief||18-19.5 mm|
|Apparent Field of View||38°-56°|
|Filter Threads Standard||1.25″(M28.5 x 0.6)|
|Blackened Lens Edges||Yes|
|Barrel Safety Recess||Yes|
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
The Explore Scientific 52 ° eyepiece line went on sale in mid-2018. It is represented by eyepieces with a focal length of 3, 4,5, 6,5, 10, 15, 20, 25, 30 and 40 mm.
In my opinion, the greatest interest for observing the planets and the moon is represented by the values of 3 mm, 4,5 mm and 6,5 mm – they are made according to the “negative doublet + Plossl” scheme.
Explore Scientific LER 52 ° 6,5 mm, 1.25 “(AR) eyepiece came to my test.
Item Number: EPWP5265–01
Coatings: EMD (Enhanced Multi-Layer Deposition) on all lens-to-air surfaces
Lens elements/ groups: 6 Elements in 3 Groups; Edge Blackened
Field of view: 52° (measured – 51,2°)
Focal length: 6,5 mm
Eye relief: 15,9 mm (measured – 16 ±1 mm)
Field Stop Diameter: 5,9 mm
Barrel Size/Type: 1.25″ O.D. / Double Taper
Filter Thread Fits Standard 1.25-inch Dia. Thread in Filters (1.125-inches x 42 TPI) (measured thread diameter – 28 mm)
Waterproof O-Ring Sealed Argon Gas Purged; Tested Under 1 Meter of Water for 30 Minutes
Eyecup: Removable Flip-Down Style Soft Silicone Rubber
Materials: Optical Glass; Aluminum; Steel; Silicone Rubber
Length: 103.5mm (measured – 104 mm)
Width: 43 mm (measured – 43 mm)
Weight: 226,8 grams (measured – with protective covers 227 grams, withot protective covers 220,7 grams)
Markings: Laser Engraved: Focal Length; Series; Serial Number; Brand
Country of origin: China for Explore Scientific (Germany)
The eyepiece comes in a beautiful cardboard box. The kit includes an eyepiece, 2 plastic protective covers and a dustproof bag made of soft fabric. The eyepiece is packed reliably, you can not worry about its safety during shipment.
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