If you own a telescope, it probably came with at least one or two eyepieces. But after a while, you may start to feel limited by the stock eyepieces.
As you begin to look at the wide variety of eyepieces, you’ll noticed that there are two main paths you can take: buying individual eyepieces, or a set of multiple eyepieces.
I’ll just go ahead and tell you right now: You should buy individual eyepieces, not a set.
Read on to learn why!
Eyepieces are not like wrenches
A few years ago, I bought a set of wrenches. It included every possible size (within a specific range), both metric and imperial.
Why did I buy a set? Because when you need an 11mm wrench, a 10mm one won’t work. If you just buy a few wrenches – say a 10mm, 5/16-inch, and 16mm – you won’t have the specific one you need when you need it. It makes sense to buy a complete set without any “gaps”.
But eyepieces are not like wrenches.
To view a given object, there isn’t one specific eyepiece that you need – there is a whole range that will work fine. So having every possible focal length isn’t all that valuable.
Eyepieces are more like cars (but cheaper)
If you bought 10 economy cars, it wouldn’t get you to your destination any faster. You can only use one car at a time, so most of them would probably go unused.
However, if you put that same amount of money into buying a high-quality car that suits your needs, you’ll have a better experience (and fewer cars to maintain).
I would recommend taking a similar approach to eyepieces. Try to determine what you want out of an eyepiece, and then buy a nice one that you’ll want to use.
Of course, you may eventually need another eyepiece to serve a different purpose. At that point, you can look for an eyepiece that suits that specific purpose.
Which brings us to another point:
Eyepiece sets don’t have much variety
Although eyepiece sets have a range of focal lengths, they usually only contain one type of eyepiece. For example, a set might have seven Plossl eyepieces.
But maybe a Plossl design isn’t the best choice for every situation. You might actually want a wide-angle eyepiece for viewing large nebulas, and a very sharp, high-contrast eyepiece for planetary viewing.
By choosing individual eyepieces, you’ll be able to mix and match different types to better suit the different types of observing you want to do.
Here’s what I recommend
If you’re at all interested in viewing deep sky objects (like nebulas and galaxies), I recommend getting a nice low-power, wide-angle eyepiece. There are a couple of reasons for this:
- When finding an object, it’s easiest to start with a low-power eyepiece since it sweeps a large area of sky. That means you’ll use your low-power eyepiece a lot.
- Lower magnification gives brighter views. So when seeking out very dim objects, a low-power eyepiece may be your best shot at seeing it.
Finding a good focal-length for low power
One important thing to keep in mind: The magnification is affected by both the eyepiece and the telescope. If your telescope has a shorter focal length, a 20mm eyepiece might give good low power views. If you have telescope with a long focal length, you might use a 30-40mm (or even higher) eyepiece.
You can calculate the magnification by dividing your telescope’s focal length by the eyepiece’s focal length. When choosing a low-power eyepiece, try to find one that gives a magnification roughly in the 40-60x range.
Apparent field of view (AFoV)
Low magnification will allow you to view a wide swath of sky, but you can go even wider by choosing an eyepiece with a wide apparent field of view (AFoV).
A wide AFoV is a bit like seeing an IMAX movie – it fills more of your peripheral vision and creates a more immersive experience. By contrast, a narrow AFoV can feel like viewing the sky through a paper towel tube.
A 60-degree AFoV is considered wide, but some eyepieces have an AFoV of 100 degrees or more (but they get very, very expensive).
Examples of wide-angle eyepieces
- Orion Expanse
- Meade HD-60
- Celestron Luminos
- Meade Ultra Wide Angle, shown below (note: some focal lengths, like the 20mm, only work with 2-inch focusers)
And if money is no object, the Tele Vue Delos, Nagler, and Ethos eyepieces are truly exceptional (and well-known) eyepieces. These would be way overkill with a cheap scope, but with a high-quality telescope they can make a noticeable difference.
Once you find an eyepiece you like, there are a few more things you may want to add to get the most out of it. For example:
- Light pollution filter or narrowband filter: This will make it easier to view deep sky objects. You can read more about telescope filters to figure out which type would work best.
- Moon filter: If you want to observe the moon, this is a must (the moon is so bright that it’s uncomfortable to view without a filter). Luckily, these are very inexpensive.
- Barlow lens: This can be placed in between your eyepiece and telescope to increase the magnification. That means you’ll be able to use your nice new eyepiece (and other eyepieces) at two different magnifications.