Navigating the many different eyepiece brands and choosing the best type of telescope eyepiece and Barlow can seem daunting, but it is easy if you remember a few basic considerations. Let us help you make an informed decision about which type(s) will best meet your specific needs! LEARN MORE
With so many eyepieces available on the market today, choosing the right one can seem daunting. Here we’ve laid out the basics for you to make a better informed decision on your next eyepiece pick! For an even more in-depth look at selecting an eyepiece, be sure to check out our comprehensive Ultimate Eyepiece Guide.
Before selecting an eyepiece, it’s important to have a thorough understanding of the key aspects that make up these observing accessories. In doing so, you’ll be better equipped at selecting the right eyepiece for your specific observing goals. Let’s take a deeper look at these critical features:
Eyepiece Focal Length
All eyepieces are marked with their focal length in millimeters (mm). The focal length of the eyepiece, along with the focal length of your telescope, determines the magnification of the image.
To figure out the magnification of any given eyepiece, just divide the focal length of your telescope in mm by the focal length of the eyepiece, also in mm. For instance, a 10 mm eyepiece used in a telescope with a 1,000 mm focal length will yield 100X magnification.
Choose a selection of eyepieces that will cover a variety of magnifications and fields of view (see below) for the types of objects you like to view best, and don’t forget to count the eyepiece you received with your telescope. Most astronomers have from 3 to 5 eyepieces and a Barlow lens in their collection. Read our Ultimate Telescope Eyepiece Guide for a lot more info on focal length and magnification!
Eyepiece Field of View
The eyepiece field of view is often listed on the eyepiece itself, but not always. Still, you can easily find it in any eyepiece’s specifications. This is the measurement most eyepiece manufacturers use when listing an eyepiece field of view. It describes, in degrees, the calculated angular diameter of light you can see through the eyepiece before it is inserted into the telescope. The simplest designs available today, such as Plossl eyepieces, have a narrower field of view that is well suited for use with the planets or the Moon. Eyepieces with a wider field, like many Celestron eyepieces, Tele Vue eyepieces, or Explore Scientific eyepieces, are perfect for large deep-sky objects such as galaxies or nebulae.
Eyepiece Barrel Size
An eyepiece barrel is the chrome portion of the eyepiece that slides into the telescope focuser or diagonal. When you see a reference to a 1.25” eyepiece, it is referring to the barrel size. The standard, and most popular size eyepiece, has a 1.25” diameter barrel. These eyepieces fit in 1.25” focusers and 1.25” diagonals, or in larger focusers or 2” diagonals when used with a 1.25 inch adapter.
2” telescope eyepieces work with 2” focusers and 2” diagonals. Eyepieces with 2” barrels are generally designed for low magnification views of faint deep-sky objects. Their larger barrel and low magnification allow the most light possible to reach your eye; a good thing if you’re trying to see a galaxy or other celestial object at the far reaches of our universe.
Lastly, there are telescope eyepieces available that have a hybrid 1.25 and 2 inch barrel, which means they will fit into either size focuser or diagonal. You may also run across .965” eyepieces for sale from time to time, but they are old-school for the most part and will not fit into the majority of current telescopes unless you have the proper adapter.
Decide which eyepiece barrel size you need before you begin shopping for a new eyepiece. If you are not sure, you can find and read the specifications in your telescope instruction manual or online. It is also easy to do a quick measurement of the eyepiece that came standard with your scope by turning it upside down and pulling a tape measure across the diameter of the opening in the barrel. Odds are, it will be 1.25”.
Eyepiece Eye Relief
Eye relief refers to how far your eye needs to be from the eyepiece in order for an image to come to focus. Eye relief is measured in millimeters (mm). Long eye relief eyepieces make observing more comfortable to all viewers but is especially important for those who wear glasses. We recommend an eye relief of at least 10 mm for all viewers and at least 15-20 mm for those who want to, or need to, wear glasses. People who have an astigmatism should keep their glasses on while viewing, but other folks can decide which works best for them…on or off.
Optical Quality
As with any optical system, the quality of your views are reliant on the lowest quality of glass utilized within your optical train. This is why selecting an eyepiece with the highest quality of glass is essential! In addition to glass quality, it’s important to be on the lookout for eyepieces with enhancements like specialized coatings and blackened lens edges. These upgrades greatly assist with improving your views by boosting light throughput, contrast, and reducing internal glare.
Click to Enlarge ImageAs we discussed above, your eyepiece’s focal length is a key determinant in what you can and cannot observe. Both magnification and exit pupil are dependent on your eyepiece’s focal length, driving how “zoomed in” you will be and the overall brightness of your image. Due to Earth’s atmosphere, there’s an upper limit to the magnification your system can achieve. This maximum magnification can be calculated by taking your telescope’s aperture in inches multiplied by 40 to 50, with a cap at 300x magnification. Staying under this calculated maximum magnification will ensure the best possible views. Use the following equation to calculate your system's magnification: Magnification = Telescope Focal Length ÷ Eyepiece Focal Length.
As for exit pupil, i.e. the diameter of the beam of light that exits your eyepiece and a factor of your image’s brightness, the shorter the eyepiece focal length, the dimmer your image will become. As a rule of thumb, larger exit pupils are better suited for viewing faint deep-sky objects like galaxies and nebulae. Smaller exit pupils, on the other hand, are typically more appropriate for viewing bright objects like the planets or our Moon. Use either of these equations to calculate your system’s exit pupil: Exit Pupil = Telescope Aperture (mm) ÷ Magnification or Exit Pupil = Eyepiece Focal Length ÷ Telescope Focal Ratio. In general, deep sky objects become visible with an exit pupil of 1-1.5 mm or greater with fainter and fainter targets becoming more and more visible as the exit pupil increases.
Plossl Eyepieces
The Plossl is a simple, four-element eyepiece design that is relatively inexpensive to produce. Most telescopes come with one or two Plossl eyepieces as standard equipment. The apparent field of view for the Plossl eyepiece design is right around 50 degrees.
When it comes to Plossl eyepieces, the longer the focal length the better the eye relief. For those who wear glasses and are shopping for the best telescope eyepiece for viewing planets or other objects that benefit from higher magnification, we recommend spending a bit more on a shorter focal length eyepiece with decent eye relief, such as the Celestron X-Cel LX Eyepiece or a Televue Delite.
Wide Angle Eyepieces
A wide angle eyepiece is defined by its apparent field of view, but what, exactly, is considered “wide”? Traditionally, a wide angle eyepiece had at least an 80-degree field of view, the most famous example being the Televue Nagler, which was designed back in 1979 with a then astounding 82 degree AFOV.
Today, you can find a huge variety of eyepieces dubbed as wide angle, ranging in an apparent field of view from 68 degrees to as high as 120 degrees! While a wide angle view is very pleasing to the eye, especially when viewing huge deep-sky objects like galaxies and nebulae, it is not absolutely necessary in any case. Wide angle really is in the eye of the beholder.
Telescope Zoom Eyepieces
A telescope eyepiece with a variable focal length is called a zoom eyepiece. The most common focal length range is 8 to 24; good examples include the popular Celestron zoom eyepiece or Baader zoom eyepiece. Sometimes, however, you get a little more range, like with this Apertura 9-27 Zoom Eyepiece.
An important thing to remember about zoom eyepieces is their field of view and eye relief will become smaller as you zoom up from the lowest power. Also, while a zoom eyepiece is very convenient, it will most likely not cover the entire range of magnification your telescope can support. So take a few minutes to calculate the magnifications a zoom eyepiece will produce in your scope and read the specifications on the field of view range and eye relief, especially if you wear glasses.
Barlow lenses are highly useful tools that essentially double your viewing opportunities. Typically rated 2x, 3x, and so on, the addition of a Barlow lens multiplies your system’s magnification by the specified rate for closer views on your targets. There are a wide variety of power and performances available with different Barlow models; let’s take a closer look at selecting the right one for you.
Click to Enlarge ImageIn order to get the most out of your viewing experience, choosing a well-matched Barlow lens for your setup is imperative. The trick is to choose a Barlow that provides enough magnification to enlarge objects without sacrificing resolution. Many telescope manufacturers highlight a “highest useful magnification” for their telescopes, giving insight into the peak magnification your system can support. It’s important to not fixate on this rate, however, as other factors play a significant role in determining which Barlow is most appropriate. Your local seeing conditions, the quality of the eyepiece you’re using, and above all, your telescope’s overall optical performance, are vital to account for as well.
Understanding your telescope magnifies everything within your field of view, including Earth’s atmosphere, poorer seeing conditions inhibit the maximum magnification you’ll be able to experience. Assessing your local seeing conditions is crucial in determining which Barlow magnification factor is right for you. In addition to atmospheric clarity, the quality of your eyepiece and telescope must also be considered. It’s important to remember your views will only be as good as the lowest quality of glass within your optical system. Higher quality eyepieces and telescopes can support higher resolution of detail when paired with more powerful Barlow lenses.
Click to Enlarge ImageContinuing on the same note regarding optical quality, it’s imperative to select a well-constructed Barlow for the best possible views. Premium glass is better adept at correcting the incoming light for sharper views and higher detail. Extra-low dispersion (ED) glass, for instance, is specially engineered to reduce color fringing, offering stark, vibrant sights of celestial bodies. This material is well regarded amongst the astronomy community thanks to its light-correcting abilities, making ED glass a popular choice in the construction of high-quality Barlow lenses.
There are a lot of great brands that we offer here at High Point Scientific, but we would like to outline the following four brands of telescope eyepieces to help you make a better decision about which will best meet your requirements. We discuss the advantages that each brand has to offer and some of the best products in each of the product lines.
Televue telescope eyepieces are legendary in amateur astronomy. Many avid astronomers use nothing but Tele Vue eyepieces and own a large collection. Not everyone can afford to buy Televue eyepieces, but if you can swing it, you’ll never have to worry about your eyepieces being the weakest link in your optical chain!
Televue has designed a plethora of eyepieces over the years, including the Televue Nagler eyepiece series, with its 82-degree field of view, the Televue Panoptic eyepieces, with an AFOV of 68 degrees, and the Tele Vue Delos eyepiece series with 20 mm of eye relief, even for very short focal length eyepieces, and a very pleasing 72-degree field. For those who have a fast, short focal length telescope, the Nagler 3-6 Zoom Eyepiece is very convenient for quick changes in magnification.
Understanding the setbacks traditional Barlows are prone to, Tele Vue set out to develop a new and improved magnification multiplier: the Tele Vue Powermates. In contrast to Barlows, these upgraded accessories eliminate vignetting, edge field aberrations, and eye relief extension, offering sharper, more comfortable viewing experiences. This is thanks to the four internal lens elements consisting of a negative doublet and a positive "pupil-correcting" doublet. With this enhanced optical design, the light rays exit the Powermate in their original direction, keeping your eyepiece's eye relief at the same distance as it would be without a magnification multiplier, and offering top-notch views at high magnifications.
Explore Scientific eyepieces came into being as a relatively inexpensive Tele Vue competitor, and they have done an excellent job creating a line of waterproof eyepieces separated into series designated by their field of view. Wait, waterproof? Yes, Explore Scientific stands out of the crowd when it comes to waterproof eyepieces. Similar to quality binoculars, these eyepieces are Nitrogen or Argon-purged, removing the worry that water will invade the optical elements and cause fogging or fungus. Of course, astronomers do not set up their telescopes in the rain, making water penetration far less likely, but waterproofing does make them easier to clean.
The Explore Scientific 68 degree eyepieces are very popular for their medium field of view and comfortable eye relief. The Explore Scientific 82 degree eyepiece series is also worth a look for those who want an immersive eyepiece experience. The 82-degree series includes a nice selection of focal lengths to choose from. Finally, our honorable mention goes to Explore Scientific 62-degree eyepieces. We like these eyepieces because they have a wider field and better eye relief than traditional Plossl’s. Eyepieces in the 62 degree series are also relatively economical choices for astronomers that want better than average quality without breaking the bank.
The focal extenders offered by Explore Scientific are unique to Barlow lenses in the sense that they can be placed anywhere in the optical train between an eyepiece or a camera. This is highly beneficial for astrophotographers where specific backfocus calculations are required, enabling seamless, hassle-free addition wherever needed. Four elements make up the optical design of these Explore Scientific focal extenders for high contrast, highly detailed views and images. Each lens is fully multi-coated and features blackened edges to minimize internal reflections.
Celestron is the biggest telescope brand in the world and so, of course, they have a nice selection of eyepieces to complement their telescopes. They even offer a Celestron Eyepiece & Filter Kit that is an amazing value for beginning astronomers who want a selection of Plossl eyepieces and colored filters to enhance views of the planets. The Celestron Zoom Eyepiece is also a very popular choice for quick changes in magnification without requiring that you switch out eyepieces each time.
Celestron telescope eyepieces are available in many focal lengths and price levels. The newest Celestron eyepiece series gives a nod to their spectacular EdgeHD telescopes. The Celestron Ultima Edge eyepieces sport a flat field for wonderful views of the planets and deep-sky objects. A flat field eyepiece produces edge-to-edge sharpness, which is also a bonus if you like to take pictures through the eyepiece!
To pair with your eyepiece, Celestron offers multiple Barlow models to choose from! The Celestron 2.5X Luminos 2" Barlow Lens is a great choice, housing four elements and offering compatibility with both 1.25" and 2" eyepieces. Thanks to its premium optical design, you can enjoy striking, up-close views without the introduction of optical artifacts. Color-fringing is kept to an absolute minimum, delivering beautiful true-color sights.
Following up on the popularity of the X-Cel LX Eyepiece Series, Celestron also offers the X-Cel LX Barlow Lens series. Two multiplication factors are available, 2x and 3x, making this series ideal for a wide range of applications. Featuring an apochromatic design, three optical elements ensure outstanding color correction for superb observing sessions.
For economically priced options, be sure to check out the Celestron 2x Omni 1.25" Barlow Lens and the Celestron Universal T Adapter & 2X Barlow Lens Assembly . These high quality Barlows are compact, versatile, and offer a closer look without breaking the bank!
Apertura eyepieces offer an economical yet quality solution for beginners building their eyepiece collection! Apertura Plossl eyepieces have a classic design and come with fold-down eyecups. Eyepiece eyecups that fold down are important for those who wear eyeglasses when viewing, while leaving the eyecup up blocks stray light from bouncing off the optics and lowering contrast.
Apertura Super Wide Angle eyepieces are a step up from the Apertura Plossl. They have a 70-degree field of view, a favorite among amateur astronomers. Apertura SWA eyepieces also have a twist-up eyecup for adjustable eye relief. Simply turn the rubber grip to move the eyecup up and down until you get the best views!
Apertura offers multiple Barlow lenses, ranging from 2x-5x magnification multiplication. The Apertura 2x ED Barlow Lens is a highly popular choice, offering stark contrast at an affordable price! This optical accessory is designed for 2” focusers and accepts both 1.25” and 2” eyepieces with the included adapter. Two ED (extra low dispersion) glass elements provide exceptional color correction within your field of view, while the multicoatings and blackened lens edges ensure maximum contrast and light throughput. For a closer look with your 1.25” eyepieces, the Apertura 3x ED Barlow Lens triples your system’s magnification. This high quality accessory is a must have for viewing the intricate craters on our Moon and getting up close and personal with the planets in our solar system.
