Sky-Watcher 9 mm Emerald 82° 1.25" Eyepiece
Get Ready for Captivating, Highly Immersive Stargazing Sessions Brimming with Detail!
Designed for astro-enthusiasts seeking high-end performance without the substantial price tag, the Sky-Watcher Emerald eyepieces are a standout choice! These top-quality observing tools deliver a rich experience under the stars with their ultra-wide 82° field of view and edge-to-edge sharpness. Perfect for immersive, high-powered viewing, this Sky-Watcher 9 mm Eyepiece is a great addition to your observing tool kit.
Thoughtful engineering is evident throughout the design of the Sky-Watcher Emerald eyepieces. Their sleek all-metal bodies, seven lens elements, and advanced broadband anti-reflection coatings ensure crisp, high-contrast sights for years to come. The impressive level of detail revealed by these observing tools rivals that of elite brands without the hefty price point, something value-minded stargazers are sure to appreciate! A custom carrying case comes standard with your Sky-Watcher Emerald eyepiece, keeping it protected during travel and storage.
Emerald 9 mm Eyepiece At a Glance
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Explore Breathtaking Views With This Exceptional Eyepiece!
With an expansive 82° apparent field of view and 16 mm of focal length, this quality crafted eyepiece provides wide and immersive window into the cosmos. Learn more about this premium eyepiece below!
Ultra-Wide 82 Degree Views
Offering more than just a “peering through a tube” experience, the wide 82° AFOV of these Sky-Watcher Emerald eyepieces levels up your observing sessions with a highly immersive feel. For reference, a singular human eye can perceive approximately 150° horizontally. This expansive 82° AFOV covers a large portion of your natural scope of vision, making for highly captivating stargazing sessions! Whether you plan to envelope yourself within vast nebulae and open star clusters or hone in on planetary nebulae and globular star clusters, the Sky-Watcher Emerald Eyepieces deliver an expansive window to the universe!
Crafted with Quality in Mind
Each Sky-Watcher Emerald eyepiece is crafted with the utmost care, ensuring exceptional performance for years to come. The CNC-machined all-metal body delivers a sleek, premium feel while simultaneously safeguarding the seven internal lenses and upholding precise optical alignment. While observing the cosmos, the soft rubber eyecups provide the utmost comfort. Included with your Emerald eyepiece is its own carrying case with a durable exterior and custom-fit interior, keeping your eyepiece snug and protected!
9 mm Focal Length
To maximize the light gathering power of your telescope, it’s important to seek out an eyepiece with a focal length that compliments your telescope’s focal length. The ratio of telescope focal length and eyepiece focal length yields your system’s magnification, a key determinant not only in which celestial objects are available for viewing but also how clear your overall image will be based on your local seeing conditions. The formula for magnification is as follows: Telescope Focal Length ÷ Eyepiece Focal Length. The addition of this 9 mm focal length Sky-Watcher Emerald eyepiece with a standard 1200 mm focal length Dobsonian yields a magnification of 133x, making it optimal for up-close sights on bright, compact celestial objects. To take a deeper dive within this topic, take a look at our Ultimate Telescope Eyepiece Guide found within our Astronomy Hub.
The Importance of Exit Pupil
Exit pupil, i.e. the diameter of the beam of light departing your eyepiece, is an important factor to keep in mind when determining which targets are best suited for your eyepiece. Large (5-7 mm) and medium (2-5 mm) exit pupils are wonderful for deep sky objects. Small exit pupils (
Frequently Asked Questions
How do I calculate magnification?
Magnification can be calculated by taking your telescope’s focal length and dividing it by your eyepiece’s focal length. For instance, if we have an 8” 1,200 mm focal length Dobsonian telescope, and we’re using the 9 mm Emerald eyepiece, the magnification will be as follows: 1200/9 = ~133.3x. It’s important to note that magnification influences how bright your image will be, as the higher magnification, the dimmer your image will become (when using the same aperture). Be sure to check out our Ultimate Telescope Eyepiece Guide for more on this topic!
What’s the difference between apparent field of view (AFOV) and true field of view (TFOV)?
Apparent field of view refers to how large the image is to your eye. For reference, a single bare human eye has a field of view of approximately 150°. These Apertura Panorama eyepieces offer an 82° AFOV for a well-immersed experience. True field of view, on the other hand, refers to the angular diameter of the “chunk” of the sky you are observing. TFOV is determined by dividing your AFOV by your system’s magnification. For instance, an 8” 1,200 mm focal length Dobsonian paired with the 9 mm Emerald eyepiece will yield a TFOV of 0.62°. The full disk of the Moon, for example, has an angular diameter of 0.5°. For more on this topic, our comprehensive Ultimate Telescope Guide provides an in-depth look!
What is exit pupil and why does it matter?
Exit pupil is the diameter of the beam of light that departs your eyepiece. It’s directly tied to the overall brightness of your image, and it’s an important factor to consider when determining which objects are available for observation. This term is analogous to our very own pupils, hence its name. As the pupil within our eye expands, more light is brought into our retina. This same concept is applicable to eyepiece exit pupils, with the larger the exit pupil, the brighter the image. Exit pupil and magnification go hand in hand; as magnification increases, exit pupil decreases, and vice versa. We measure the exit pupil by its diameter in millimeters. To calculate the exit pupil of your eyepiece/telescope combination, use either of the two equations: Exit Pupil = Telescope Aperture (mm) ÷ Magnification or Exit Pupil = Eyepiece Focal Length ÷ Telescope Focal Ratio.
Astronomy Hub: Your one-stop-shop for Astronomy Knowledge!
Our Gear Experts have compiled a wealth of information to help you get the most out of your telescope! Below you’ll find links to articles, videos and "how-to" guides. Just one more reason that our Astronomy Hub is a one-stop-shop for all your astronomy and astrophotography needs!
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