A telescope zoom eyepiece allows you to have several telescope eyepieces installed in your telescope at one time, making viewing easier and faster. In addition, this also allows you to spend less money as one zoom eyepiece can cost less than the several eyepieces you would have to buy to give you the same views.
If you have a typical beginner telescope it probably came with one or two Plossl eyepieces. Looking around a reasonable Plossl eyepiece can run $30-$50 on average. If you assume $40 and the typical zoom eyepiece allows five magnifications, that is the equivalent of $200 worth of eyepieces.
While having a zoom makes you wonder why anyone would ever buy a regular non-zoom eyepiece that answer is simply, optical quality and field of view. When considering a zoom eyepiece or fixed eyepiece, you have to decide between saving time and money or getting the best image quality you can.
Zoom eyepieces are just like zoom lenses on cameras in that in order to make them work on a variety of different focal lengths, sacrifices have to be made and this usually results in the zoom lens being inferior optically to a fixed focal length lens. Of course, you may not even notice the degradation in optical quality, particularly with beginner telescopes and inexperienced users. Many beginners like to start off using zooms so they get a feel for what eyepieces they really need.
In addition to the optical degradation, zooms are generally restricted to between 40-60 degrees field of view. This is about the same as the typical Plossl (50-55 degrees). High-end zooms can run as wide as 68 degrees bringing them up in line with midrange eyepieces such as Baader Hyperions, Orion Q70s, and Tele Vue Panoptics.
These higher-end zooms also tend to rival the optical quality of standard eyepieces unless you intend to push them to the very edge of their performance. In layman terms, unless you have a medium to high-end telescope and years of experience, you would be hard-pressed to see much of a difference between the higher-end zooms and fixed focal length eyepieces.
The three best telescope zoom eyepiece choices
The Astromania 1.25″ 8-24mm Zoom Eyepiece is an excellent introduction to telescope zoom eyepieces. With excellent eye relief and a 40-60 degree field of view, this is the perfect replacement for your Plossl eyepiece collection. The addition of 1.25″ filter threads on the base and t-ring threads on the top make this a very flexible choice.
The threads on the nose allow you to add any 1.25″ filter such as light pollution filters, ultra-high contrast filters, or a simple moon filter. This is particularly convenient since you will be using this one eyepiece at several different magnifications.
The T-Ring threads on the top allow you to connect your camera using a T-Ring adapter (assuming you have a camera with removable lenses) so that you can take pictures without having to purchase another adapter. Of course, you will have to buy the T-Ring that mates with your camera and screws onto the end of this eyepiece but those are very inexpensive.
While the optics are nothing to write home about, they are more than sufficient to use in a beginner telescope with most targets a beginner will be observing.
The Celestron 93230 8 to 24mm 1.25 Zoom Eyepiece has roughly the same field of view, filter threads, and eye relief as the Astromania above but lacks the T-Ring threads on the top. Why is it more expensive then? Because the optics are far superior. This eyepiece comes very close to the same optical quality as a hand full of medium grade Plossl eyepieces.
This is also a fairly substantial eyepiece just feeling a little more solid in the hand than the Astromania version, not just in weight (it is about twice as heavy) but also in build quality/materials. I also liked the rubber eyecup on this one better than the Astromania version although that is a bit subjective.
If you are looking for something good, and are not sure you want to commit to more serious astronomy gear, then this would be an excellent telescope zoom eyepiece to add to your kit.
When you want a really nice eyepiece, that also just happens to zoom, the Baader Planetarium 8-24mm Hyperion Clickstop Zoom Mark IV Eyepiece is what you want. Fully multicoated world-class optics, 68-degree field of view, twist-up eyecup, filter threads, available T-Ring adapter, and it fits both 1.25″ and 2″ focusers. If you have ever used a Baader Hyperion (or Orion Stratus) eyepiece, then you already know the quality of the equipment they make, and this is no exception.
Yes, this Baader zoom eyepiece is very expensive compared to the other telescope zoom eyepieces, but with its superior optics and 68-degree field of view this eyepiece doesn’t replace five $50 Plossl eyepieces, it comes closer to replacing five $147 Hyperion eyepieces.
I also like the fact that this is a substantial eyepiece weighing 33% more than the Celestron and 100% more than the Astromania. That may seem like a downside but it really isn’t as the extra weight makes it much more solid and easier to handle. The rubber grip around it is also grippier than either of the other two eyepieces so again, it tends to stay in your hand better. You would be surprised how that extra weight works when your hands are cold or slippery with sweat.
While I could write an entire Baader zoom eyepiece review, it can be summed up by saying I am not convinced that this eyepiece is as good as the fixed focal length Baader Hyperions, and it certainly is not as good as a Tele Vue Pantopic, it is an excellent eyepiece where you will be hard-pressed to find faults in all but the most extreme conditions.
No Baader Hyperion zoom mark iv review would be complete without mentioning that Baader makes a wide array of adapter to use on their eyepiece. You can visit the manufacturer’s website for more information if you are interested.
There are a lot of other zoom eyepieces out there on the market but these are the ones I would highly recommend you take a look at adding to your equipment.