Using the right telescope eyepiece will ensure you get the best view of the starry night sky, which is why you should pick out the best telescope eyepieces.

How To Choose A Telescope Eyepiece

Which is more important, binoculars or eyepieces? Binoculars get a lot of attention because they are the most expensive and impressive part of your telescope kit, but without decent eyepieces the results you get can be very disappointing.

Ideally, you need a set of telescope eyepieces that are suitable for observing, as different focal lengths help to better observe different types of objects. Depending on the telescope used, each telescope eyepiece has a different field of view and magnification.

Size Matters

Finding the magnification of the telescope eyepiece is very simple, you can get the result by dividing the focal length of the telescope by the focal length of the eyepiece. The focal length of the telescope is usually marked on the nameplate near the eyepiece end. Decent eyepieces have their focal lengths in millimeters and are marked around the rings. For example, to calculate the magnification of an 800mm focal length telescope with a 25mm focal length eyepiece, simply divide 800 by 25, which equals 32x magnification. This combination will magnify the object you see in the eyepiece by 32 times.

Telescope Eyepiece magnification

For more expansive nebulae and star clusters, this is the magnification you want. To get higher magnification, perhaps you’d use a 10mm eyepiece, and then you’d get more detailed images of planets and binaries. As you progress in astronomy, you’ll no doubt start experimenting with various telescope eyepieces to provide different perspectives. So, don’t underestimate these seemingly inconspicuous astronomical accessories!

Know Your Telescope Eyepiece Types

telescope eyepiece types

There are 4 main types of telescope eyepieces and a Barlow lens increases the magnification of the eyepiece.

1. The Plossl Eyepieces

With its wide field of view (about 52 degrees), the plossl eyepieces can be used successfully for planetary and deep space observations. The disadvantage of plossl eyepieces is that the focal length is 12 mm or less, resulting in a very short pupil exit distance. The pupil exit distance is how far your eye must be from the eyepiece to see the entire field of view.

The internal structure of a plossl eyepiece consists of two back-to-back lens systems. There is a big price difference between the best quality plossl eyepieces and those cheaper products.

2. The Radian Eyepieces

The Radian eyepiece is one of the newer telescope eyepieces on the market and has a similar field of view to that of the Plossl eyepiece. You may be wondering what the difference is: the Radian eyepiece has a long exit distance, even though it has a focal length of only 3 mm. It will be your savior if you need to wear glasses when observing. The Radian eyepiece is designed for medium and high magnifications so that you can see enough detail when observing the planets. Inside the Rydian eyepiece, there are six or seven lens elements with very short focal lengths.

3. The Nagler Eyepieces

The most impressive feature of Nagler eyepieces is their huge field of view. While other manufacturers keep the field of view of their eyepieces within 50 degrees of the human eye, Nagler has gone the extra mile to develop a telescope eyepiece with an extra-wide 82 degree field of view. Imagine the amazing views you can get of the stars and nebulae! The Nagler eyepiece contains 6 or 7 elements, all of which are coated with special chemicals to improve the light throughput of the eyepiece. The disadvantage of this type of telescope eyepiece is the weight, which may require you to rebalance your telescope.

4. The Orthoscopic Eyepieces

There were many other telescope eyepieces that were the preference of many amateur astronomers before the plossl eyepieces made their mark, but aberration-free eyepieces are still great little eyepieces. They have a quadratic optical system and have a great exit distance. The Orthoscopic eyepieces are also designed to be very effective in reducing the amount of light lost to refraction within the system. Although their field of view of 40 to 45 degrees is not as large as that of the plossl eyepieces, they are still quite good and versatile. They are particularly useful in moon and planetary observations.

Doubling The Magnification With A Barlow Lens

Magnification With A Barlow Lens

This is a remarkable tool. It is not actually an eyepiece, but simply an optical element that is paired with an eyepiece to increase magnification. It is achieved by a very simple process: insert the eyepiece into the Barlow lens and place the whole unit in the position where the eyepiece would normally be mounted. With a Barlow lens you can double or triple the magnification of the eyepiece. This means that by using a Barlow lens you are effectively doubling the number of eyepieces and thus the magnification.

Enjoyed this article on choosing a telescope eyepiece? Then be sure to check out our other guides of the Best Refractor Telescopes and the Best Reflector Telescopes.