SVBONYSV215 Zoom Eyepiece, 1.25 Inch Zoom Lens, 3mm to 8mm Eyepiece with Parfocal Design, Telescope Accessory for High Power Lunar and Planetary Observing

I have been a lunar and planetary observer for over 60 years and a retired optical engineer. Planetary eyepieces are easier to test for aberrations due to their smaller AFOV. They are optimized for viewing objects in the center of the field.When visually observing planets, the main requirements, in order of importance, are sharpness, contrast, and color fidelity. In my experience, the best planetary eyepieces are simple, time-proven designs with the fewest elements (less than 6). Today's visual observers are primarily interested in observing deep-sky objects using wide-field eyepieces with 4 times more lens elements than traditional planetary eyepieces. Some younger observers have never observed the planets with high-quality 3 to 4 elements eyepieces. The Svbony has 6 elements, but it is a zoom eyepiece, and it manages to perform admirably.Jupiter is the premier planet to test eyepieces due to the low contrast of features in the belts and zones. It doesn’t take magnification as well as Saturn, so you can quickly see differences.I didn’t evaluate comprehensively to determine if the Svbony falls short. With good seeing, if you can’t see any difference in the first 30 minutes switching eyepieces in and out, there is little reason to spend more time seeking an answer. If it takes this long, then there is no practical difference. Over the years, I spent too many hours at the telescope over several nights to arrive at a final verdict. To what end? This is time better spent observing.The performance of this eyepiece is outstanding. I had a selection of eyepieces to compare with the Svbony zoom, i.e., 3, 4, 5, 6, 7, and 8 mm. Some were high-end eyepieces, including orthoscopics, Plossls, Televue Radians, and Delos. After an hour of observing, I could not see any significant differences in the image quality of the Svbony compared to the other eyepieces. In a few cases, the expensive widefield eyepieces with many lens elements faired worse in detail. While image brightness and contrast were good, the definition of delicate structures in Jupiter’clouds was lacking.Zoom eyepieces usually require refocusing when switching focal lengths. My sample was parfocal. Depending on the seeing, when focused at the shortest focal length, 3 or 4 mm, there was no need to refocus at the 5, 6, 7, and 8 mm settings.In summary:Likes: Cost. Functionality (beats switching eyepieces). Mechanical quality (parfocal, click stops). Optical quality (sharpness, contrast, flat field)Dislikes: Heavy (built like a tank). Tapered eyepiece barrel (hard to clamp with compression ring). The eyepiece barrel length is too long. The barrel cap keeps falling off.A good analogy between a zoom eyepiece and a fixed focal length eyepiece is a Swiss army knife compared to a hunting knife. Svbony has managed to even the playing field. I highly recommend this eyepiece for owners of short focal length refractors (less than 800 mm).

This is essentially a clone of the TeleVue 3-6mm zoom, but with an extended range. I’ve been using it with my TV-85 and Pronto, and I’ve been very impressed with the performance, particularly after being very unimpressed with Svbony’s 8-24mm zoom. Is this one as good as the TeleVue? No. But it’s very good, especially given that is costs a third of what the TeleVue does, and you get that extra 7-8mm range. The field of view doesn’t narrow as you zoom in, and it’s pretty much parafocal throughout the range. It won’t be as sharp as individual eyepieces, but the convenience of a zoom can be worth the difference, especially in terrestrial viewing.Whether of not you should buy it depends very much on the telescope you plan on using it with. Used with an inexpensive short-focus doublet refractor or the typical reflector, images will be disappointing. In a 8” SCT, that 3mm translates to 667x- far more than such a scope can support. You need a scope that can support high magnification- a long focus (f/12-15) refractor or an apochromat.

wow this is a pretty decent eyepiece, I saw a you tube video recommending this as a budget / quality high power zoom lens. I am very pleasantly surprised... This is in no means a Televue but for the price the quality is quite good.beware this is a HIGH power eyepiece and the image will be a little dim due to the very small exit pupil.

This item was NOT provided by VINE.Zoom eyepieces? "No way!" will most seasoned astronomers say - "they cannot have good image quality..."I am currently looking at some of our planets and like to see some details (e.g. Saturn's rings, and Jupiter"s bands). I have been using multiple fixed focus length eyepieces and Barlow lenses and gotten some results, but the process of going from a big eyepiece to increasingly smaller ones, and/or adding Barlow lenses, is a cumbersome one, definitely for the Noob...I ordered this eyepiece with Amazon's fair return policy in mind. I had a favorable Youtube review , but I still did not expect much.Let's say it upfront: This Zoom Eyepiece is great and not going back.With my Dob I needed one 26mm eyepiece to find and center the planet. Once centered I inserted the zoom eyepiece. After I refocused to the 8mm starting focal length I was stunned. I have a dedicated name-brand 7mm eyepiece and this image looked so close I probably would not be able to tell the difference in a blind test. I then started to Zoom in, and it was fantastic. The image quality up to 6 mm was still excellent, at 5 and 4 it dropped a little bit, but not dramatically. At 3mm it was slightly blurry, but this is also close to the maximum possible magnification of my telescope.Still, I had never been able to reliably bring Saturn or Jupiter in below a 7mm lens. This was largely due to the cumbersome process of changing eyepieces and adding or removing Barlows, all on a Dobsonian without goto mount.With this eyepiece, I was able to go down all the way to 3mm. And rather than the rushed job that it is with dedicated eyepieces and Barlows, I enjoyed the journey. If a planet gets out of view, it generally is possible to bring it back by zooming out, whereas without Zoom it would mean "eyepiece change" (and often not just once). What a huge difference.But Image quality? No, it's not as good as dedicated Tele Vue eyepieces, but it is very good. I do not see that I missed anything at 8-6mm, and even after that it was still very good.The old-school astronomers are still correct, but not by much anymore, and when one counts in the convenience, this is highly recommended, in particular for beginners.