Orion 15 mm Sirius Plossl 1.25" Eyepiece
Explore the Cosmos with this Exceptional Eyepiece
The Orion 15 mm Sirius Plossl 1.25" eyepiece offers exceptional views at an affordable cost. This moderately high power eyepiece pairs well with any telescope, making it a great addition to your eyepiece collection. Whether you are looking to enjoy a "full-disc" view of our Moon, or bright deep sky objects, such as Bode's Galaxy (M81), this 15 mm eyepiece is well-suited for the task!
The Orion Sirius eyepieces are designed to provide sharp, comfortable views. Each eyepiece in the series features fully multi-coated optics that improve light transmission while reducing internal reflections. The 4-element Plossl design provides a well corrected 52° field of view, allowing stars and other objects to remain sharp across much of the field. The eyepiece body features precise CNC-machined components and is threaded to accept standard 1.25 inch telescope filters. It also includes a “Fold-Up” rubber eyecup, which blocks stray light while providing a more comfortable viewing experience.
15 mm Sirius Plossl Eyepiece At a Glance
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Crafted with Quality and Comfort in Mind!
This Sirius Plossl eyepieces are crafted to deliver comfortable and immersive views. They are equipped with a standard 1.25-inch barrel and will fit any telescope that accepts 1.25-inch eyepieces. Read on to learn how these premium eyepieces will provide you with a breathtaking window into the cosmos!
15 mm Focal Length
The Sirius Plossl eyepieces make an excellent addition to any eyepiece collection, but knowing which eyepiece best compliments your telescope's focal length will help you select the right one for the job. For example, pairing this 15 mm Sirius Plossl eyepiece with a standard 1200 mm focal length Dobsonian provides a magnification of 80x, making it optimal for enjoying a "full-disc" view of our Moon, or bright deep sky objects, such as Bode's Galaxy (M81). If you want to learn how to select the best eyepiece for your telescope and target, check out our Ultimate Telescope Eyepiece Guide!
Crafted with CNC-machined Components
Each Orion Sirius Plossl eyepiece is crafted with optical quality and comfort in mind. The CNC-machined body maintains the precise optical alignment of the internal lenses while also providing a sleek, premium look and feel. The soft "fold-up" style rubber eyeguards work to block stray light while also delivering a comfortable viewing experience. These premium features ensure you'll enjoy exceptional performance for years to come.
Threaded to Accept 1.25" Filters
Adding a visual filter to your eyepiece can make all the difference when it comes to drawing out more detail from bright celestial objects, which is why this 15 mm Sirius Plossl eyepiece is threaded to accept standard 1.25-inch filters. With this eyepiece, you'll have no trouble enhancing your views with all sorts of filters, such as the Apertura 1.25" Moon and Skyglow Filter (sold separately), which significantly reduces the effects of light pollution while also increasing contrast levels seen within your eyepiece. If you are looking to uncover even more hidden details, the Apertura 1.25" Lunar & Planetary Filter Set (sold separately) is an excellent way to boost your viewing potential!
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 a 15 mm eyepiece, the magnification will be as follows: 1200/15 = ~80x. 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°. The Orion Sirius Plossl eyepieces offer an 52° 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 a 15 mm eyepiece will yield a TFOV of 0.65°. The full disk of the Moon, for example, has an angular diameter of 0.5°. For more on this topic, our comprehensive Ultimate Telescope Eyepiece 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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