We Have Canada's Best Selection of Telescope Eyepieces
We’ve tried all kinds of eyepieces in our personal telescopes, and we're constantly reminded of how much a telescope's performance depends on quality eyepieces. It’s the reason that we have been so careful in putting together our selection of eyepieces here at All Star Telescope.
Most telescopes come with one or two starter eyepieces, these are designed to get you out under the stars right away, but to get the most out of your telescope, you may need to look at upgrading or adding to your eyepiece collection. Picking the right eyepieces can be hard though, and what do those little numbers mean anyway?
Telescope Eyepieces Change Your Telescope's Magnification
Magnification on a telescope is a simple calculation of the focal length of the telescope divided by the focal length of the eyepiece. For example, a NexStar 8SE has a focal length of 2,032mm, so a 10mm eyepiece will yield 203x magnification. Just remember that the more you zoom in, the narrower your view gets. Not everything looks best under high magnification, and many objects won’t fit into your field of view at 200x.
How to Choose Eyepieces for Your Telescope
The first step in picking the right eyepiece is deciding what you’d like to see. Most beginners start out wanting to get more detailed views of the planets, seeing the rings of Saturn, or bands on Jupiter.
For viewing the planets, we prefer magnification between 150x and 200x in most seeing conditions. Beyond that, image quality is limited by seeing conditions (atmospheric disturbance, light pollution, etc.). For most beginner scopes that means a 5mm eyepiece, for most Dobsonians that means a 6mm-8mm eyepiece, and for most NexStar’s that means something a 7mm-10mm.
After enjoying the moons of Jupiter and the rings of Saturn, most astronomers move on to other objects like star clusters, double stars (binary systems), galaxies, and nebulae. While you can never have enough eyepieces, we find most people wind up favoring about 3 eyepieces. One high magnification, one medium magnification eyepiece, and one low magnification wide-field eyepiece. As a rule of thumb, you should approximately double focal length between each eyepiece.
That means that for a beginner telescope or something with 500-700mm of focal length you’d want to wind up with good quality options around 5mm, a 10-12mm, and a 20-24mm eyepiece. For a Dob looking at eyepieces around 7mm, 15mm, and 30mm will be about right. For something like a Celestron NexStar something around a 10mm, 20mm, and 40mm would give you great options. These are just guidelines, getting some time outside with your telescope will help you to narrow down your preferences so that you can tailor your choices.
Telescope Eyepiece Brands
Tele Vue eyepieces are legendary, but we also carry excellent eyepieces from Baader, Pentax, Explore Scientific, Celestron and more. We're always happy to provide advice on choosing a great telescope eyepiece. As a rule of thumb, in the $150-$200 range we think that Celestron gives you the most bang for your buck. Between $200 and $300 you can’t beat a Baader. Above that and you’re getting into some premium options where personal preference will play a larger role.
Seeing Conditions Will Still Limit a Great Eyepiece
Sky conditions and the position of the celestial body in the sky will play a huge part in the “sharpness” or “clarity” of the view. When viewing objects like planets closer to the horizon, you are looking through two or three times as much atmosphere as higher in the sky. That atmosphere is often turbulent as the air warms and cools from the heat of the earth and may have more haze or low cloud. Telescope eyepieces can’t overcome those effects. A moonless night, no light pollution and higher elevation with thinner air will contribute to better viewing.
A Barlow Lens for Your Telescope
A Barlow lens increases magnification on your telescope's eyepiece, usually by a factor of 2x or more. So if you use a 2x Barlow with a 20mm eyepiece, it effectively becomes a 10mm eyepiece but at the cost of some reduced clarity and sharpness. The idea is that two eyepieces and a Barlow will give you the flexibility of magnification of four eyepieces, and will give higher magnifications with less powerful eyepieces.
Other Things to Consider When Buying Eyepieces
But some brands offer the same magnification and “field of view” of the TeleVue eyepieces. Yes, but there are other qualities in an eyepiece to consider.
Field of view - you will see an eyepiece characteristic called “Field of View” While this is not the same as magnification, it has to do with how much of the sky you can see - are you looking through a tunnel or through a picture window at the night sky? Wider fields of view are almost almost more enjoyable. Al Nagler developed the 82 degree field of view Nagler eyepiece which continues to be one of the best quality eyepieces. Now the TeleVue Ethos offer a 100 degree field of view so when you look in the eyepiece you almost only see the sky rather than the edge of the field of view. The basic eyepiece(s) that came with your telescope likely offer 50 degree field of view.
Eye Relief - how far does your eye need to be from the eyepiece to see the entire field of view. You may find the basic 10mm eyepiece that came with your telescope has a “peep hole” and your eyeball is almost touching the eyepiece to see the entire field of view. You’ll want a minimum 12mm of eye relief and even more if you wear glasses when viewing. The TeleVue Delos line of eyepieces all feature 20mm of eye relief and are a favorite of those wearing eye glasses
Glass quality - a cheap piece of glass in an eyepiece likely will not give pinpoint stars at the edge of the field of view. Typically they will look like comets and produce what is called “coma” If it is advertised as offering an 82 degree field of view but only 68% of the view is sharp, it is a low quality eyepiece. Additionally cheaper glass will allow a small amount of light from stars to bounce around in the imperfections of the glass resulting in the sky becoming gray and reducing the amount of starlight coming through to your eye. You’ll want the best glass with the best coatings for the best viewing.
What Will I See Through the Eyepiece?
Getting out with the telescope under the nighttime sky can become a lifelong hobby and passion. In his book, Seeing in the Dark, Timothy Ferris says, “The universe is accessible to all, and can inform one’s existence with a sense of beauty, reason and awe as enriching as anything to be found in music, art of poetry.” If you're looking for a more concrete answer, it depends. Most of our telescope product pages come with field of view previews that will give you an idea of what you’ll see. If you have a question or need help choosing, we're always happy to help.