Celestron 8-24mm Zoom Telescope Eyepiece with Fully Multi-Coated Optics

I purchased this in April 2011-after the March Supermoon and it quickly became my primary eyepiece! AFOV is wider than my standard MA (Modified Achromat) eyepieces and the wide exit pupil allows for an easier stance over whatever telescope I am using at the time of viewing. I will admit that while adjusting the zoom the view would often show some distrortion, but, in the beginning, I was able to spin the zoom function back and it would self correct. Over time, that 'self-correction' stopped unless at either stop (8mm or 24mm focal length). Problems: 1) See above for distrortion issues. (Mine may have passed QC by mistake). 2) Weight. Small, beginner scopes are impacted severely. Most impacted are refractors, as they 'balance' on the mount. 3) No clicks during focal length. Must turn on light to see where length is. 4) Overall EP assembly gets loose. I needed to tighten the chrome sleeve to the body of the assembly every time I used it. 5) Mine cracked during use on a cold night? The focus changed and the view went distorted. No visible broken glass, but, something went loose (I can hear it when I shake the EP!) With these things noted, I must say that while it worked- it worked great. I'm not sure if all of the glass was mutli-coated because I did get quite visible reflections- but, the view was clear with a nice big exit pupil. So large in fact, I was able to use a high quality, multi-coated (multi lens) 3x achromatic Barlow lens with it- creating very crisp lunar views under exceptional seeing conditions. However, that only worked on my largest GOTO scopes: a 90mm refractor & 114mm reflector-both of which needed to be balanced with all of that weight mounted. Anything smaller was at risk of toppling over and could not be locked down hard enough to bear the excessive load. So, if you have a smaller manual refractor, say 60mm, 70mm or 80mm or even a smaller manual reflector- make sure that your mount will bear the load and that you can acheive balance prior to buying one of these. Otherwise, you'll be very frustrated! I strongly recommend this EP to someone who has limited funds for buying a variety of high quality lenses. If purchased with a very high quality 2x Barlow, it will cover many lenses that can be purchased separately. I think mine passed QC in error, or was dropped during shipping because my distrortion issues & constant need of tightening haven't been mentioned by other reviewers. Also, I cannot imagine that mine would 'crack' during use, unless something was already defective. Now, I'm hoping that Celestron will repair or replace mine (it's still under warranty), but, I don't want my issues to prevent someone from seeing the value in this pretty high qaulity eyepiece. The glass is very clear, the exit pupil is very forgiving and the views can be tremendous! Clear skies to all! Dave

Wow! This eyepiece might never leave my scope! The optical quality is great throughout the zoom range (as much as seeing will allow), requiring only tiny adjustments in focus on my Celestron 8SE. The field of view is noticeably tighter than the standard 25mm piece that comes with my scope, but that actually helps me center objects when aligning. The field of view is still large enough for the goto mount to put the object in view, especially if you know how to use the precise goto function, so that should dissolve your one worry about using this. The zoom is magnificent. Saturn was stunning at mid-high power (the highest power in my scope is over 250x, which is not going to look good in anyone's scope without good seeing), and the view is crystal clear at lower power. I was able to spot at least five moons around Saturn from the light polluted skies of Pasadena, CA where hardly any stars are visible. Higher power dims the image, but I did not notice any strange optical peculiarities. I'm sure there are some, but for me this eyepiece is a dream come true. I was even able to view the ring nebula from my front yard, and with medium power I was able to discern the two protrusions from the edges, a big step up over the meager 80x offered by the standard eyepiece. The ability to zoom on the fly makes keeping the target in the field of view incredibly easy. The piece is quite heavy because of the extra complexity, but doesn't feel overly bulky. The zoom is controlled by twisting the textured part of the outside, which others have reviewed to be rather stiff and difficult to turn. I can't join that chorus, as i have no problem zooming out so long as I grip the smooth base and twist the textured sides. The action is smooth and holds firm. Basically, this thing is amazing. I would pay twice as much for this and still feel like it was a bargain.

This zooming eyepiece does a great job, but you need to be aware that somethings do not appear as well as others when zoomed in. This is an inescapable fact of life. Additionally, as with any zooming optical piece, the more you zoom in the smaller the field of view becomes. This means that the object can become too big to see all of it in the eyepiece when zoomed in depending on how big it appears to start with. The moon, for instance, will go from filling the whole eyepiece to just 1/6 of it filling the whole eyepiece. This is, again, just the nature of optics and is no fault of the manufacturer. But for viewing much farther away objects this zooming eyepiece is excellent at making them appear larger, which can greatly increase the detail visibility. Note: there are many objects for which the optimal view is a finite point in the range of zooming. For those objects, it's best to find that sweet spot and not try to zoom in too much. Also, it's best to turn the barrel, the zooming, slowly to find that right spot. The main reason for having a zooming eyepiece is to avoid having a dozen different sized eyepieces, any eyepiece within the range of this eyepiece becomes redundant. Thus, it's fine to have a 4mm eyepiece as this one only goes down to 8mm, or to have a 32mm since this one only goes up to 24mm. The base of this eyepiece has a threaded adapter which allows filter inserts to be mounted to the eyepiece. And, it comes with its own nice protective container. The container has a threaded lid that screws on, and the lid has an extension that fits the bottom of the eyepiece -- the eyepiece fits in the container upside down. The bottom and the top of the eyepiece also come with rubber dust caps. All in all, this eyepiece is very much worth buying for its convenience, function, and the fact that with it one does not need a handful of specifically sized eyepieces.

Please note the following remarks are based on lens use with an f/10 SCT, Celestron 5" Omni. I received this and immediately inspected it. Nice coating and during use seems to be essentially glare-free. Not exactly parfocal but requires only minimal refocus post-zooming. Field of view (FOV) is less than listed in product description, so even at mid-magnification one will only see Jupiter and its four primariy moons within the FOV, at least in this scope focal length. Of course, with the f/4's and f/5's, you would obtain much wider FOV's. Higher magnifications, as with any lens, loses defining ability but nothing that is beyond individual lenses of the same powers. In fact, in comparison at 9mm through 15mm, I found this zoom apparatus to be better than another well known company's plossls. Recommended? Yes! Functions well for stars, for higher emission nebula (Orion), a brighter galaxy (Andromeda), and the gas giants. But open clusters such as the pleids, those in Auriga, and the Beehive in an f/10 extend beyond the FOV even at 24mm focal length and require minor scanning. For terriestrial viewing, this is an absolutely excellent lens system and the zoom is a joy to use with minimal loss of defining ability beyond ~22mm. Still, this will match and even outperform other zoom systems costing up to $150.00. Last point: at low night temp's., turning the zoom is a necessarily slow process so one won't skew the scope off-track. Nonetheless, unless you are a perfectionist/purist, you will not be disappointed. Good Viewing and Clear Skies!

I'm using this on a Celestron 102mm F5 telescope. While heavier than a standard eyepiece, it eliminates having to change out eyepieces with the chance of dropping one. (I have a old 40mm with a chipped lens from just this). On the Celestron it gives 21x to 63x. Eye relief is ample for eye glass wears at the 24mm end, but shortens down to where you won't be able to see the entire field of view (with glasses) at 8mm. I haven't had much chance to use this yet under the stars, but on things that I could view, the view appeared just about as sharp as with a regular eyepiece. The one major difference you will notice when you receive this is that it is larger and heavier than ordinary plossls. The rubber eyeguard can be reversed so that you don't need to turn it down if viewing with glasses. You may have to rebalance your telescope due to the somewhat greater weight compared to ordinary three and four element single power eyepieces. Stated weight is 4.8 ounces. It also comes in a real nice case with a screw top as well as a rubber top cover and a plastic slip on cover for the bottom. The image appears sharp over the field of view (an F5 telescope is a bit more demanding of eyepieces than say an F10 refractor). So this is a good eyepiece considering that it zooms from 24mm to 8mm. Apparent field of view is 40 degrees at 24mm and 60 degrees at 8mm. Refocusing is necessary in going from long to short or vice versa, but it isn't too much trouble. Much easier than swapping out eyepieces in the dark anyway...

I purchased this eyepieace for my Celestron C90 MAK (ships with a 32mm eyepieace). The C90 MAK is 1200mm focal length, i.e. the 8-24mm translates to x50-x150 (divide the focal length by the eyepiece focal length for the magnification). The eyepiece easily connected to the telescope - standard 1.25" diameter. The image initially appeared clear. My first target was the moon. It was a bit bright, but if I really want to do many lunar observations I should get a filter. Then came the real pleasure - I looked at Jupiter. With the original eyepiece I have, all I saw was a dot. At the lower magnification (24mm), I saw Jupiter with what I thought might be a few moons. As I zoomed in, I saw the moons more clearly. Some focusing showed the moons very clearly, but initially I thought Jupiter might be off-zoom, then I realized I'm seeing the planet as a real object, it was in focus but I could see that it has some size to it (not the way you see a distant star, more like the way you see the moon). And all of this was close to a full moon at an urban environment. Highly recommended. I love this eyepiece and the fact I can zoom in and out. It does not seem to lose much light (which was my concern when I originally bought it).

So, if you're like me then you've probably heard a lot of terrible things about zoom eyepieces. They kind of fall into the same boat as Barlow lenses: they exist, but any "pro" will tell you to never go near these sacrilegious pieces of junk. When I was first getting into amateur astronomy I spent countless hours reading through forums and gathering as much information as I could from these "seasoned veterans" in order to make the best possible purchase decisions. Over time, I have come to my own very different conclusions. I believe the technology has improved so much in the past few years that the original stigma associated with zoom lenses is largely vestigial. I consider myself to be a hobbyist; I make no claims to being some elite seasoned astronomer. I'm simply an amateur that enjoys spending a couple nights a week gazing into the cosmos, and if you consider yourself to be in the same boat then BUY THIS EYEPIECE. When this zoom first came in, I spent an hour or two comparing the image quality of different steps of the zoom to equivalent focal length Orion Sirius Plossl eyepieces. My verdict? There was absolutely NO reason to use the Plossls. AT ALL. I am so pleased with this eyepiece that I don't even bother taking my fixed focal length eyepieces on most trips any more. For the price and the utility that this zoom offers, there is simply no better deal. The fact that there is a built in T-thread for astrophotography is simply icing on the cake. The eyepiece comes with a nice hard plastic shell that makes transporting it safe and easy. It is a little bit on the heavy side, so if you are equitorially mounting your scope, you will probably have to re-balance the whole deal. If anyone is wondering about measurements here are a few estimates, NOT INCLUDING the base that should sit inside of your focuser / Barlow lens: - With the eyecup up: 8.5 centimeters - Without the eyecup: 7.25 centimeters Regarding the zoom action, it is stiff enough that you won't accidentally shift focal lengths, but it is also smooth enough that you can rotate it without holding the base of the eyepiece with your other hand.

I used this in an 8" F/6 manually guided reflector (providing 50-150x magnification), and I use it mostly for visual use. As a visual zoom this is very convenient for star parties and the like, when you don't want more expensive eyepieces getting dropped. As with all zooms, expect a decent apparent field of view at the highest powers, but a reduced apparent field of view with higher powers (this is the "looking down a tube" effect common with most/all zooms). It's not quite parfocal, but required focusing was negligible. The magnification ring is stiff, with no clicks. If it's not secured very tightly in your focuser, the entire eyepiece will rotate when you attempt to change magnification. Eye relief was good (and I wear eyeglasses), again making it good for star parties. The outer edge does show coma at f/6 and is slightly distorted in general. For casual, single exposure eyepiece projection photos with a DSLR and an alt-az mount, you can get great moon shots, and adequate planetary shots, but expect significant light loss and vignetting when using it for photography via the t-ring with a basic unmodified DSLR.

I first could not achieve focus with the scope I have. This is probably because of the nature of Newtonian reflectors. However, with a zero-profile adaptor, I was finally able to achieve focus. It may also help to use an adaptor that is recessed (negative profile). The zoom feature is great, but image quality deteriorates rapidly at higher magnifications. Still, it is convenient to have the zoom feature, where you don't have to change eyepieces and re-focus while holding the telescope steady in the meantime. The build quality is excellent, although a bit on the expensive side. Recommended, if you have the right eyepiece adaptor (or scope).

Excellent

Great eyepiece to have when you feel like 'surfing the sky'. The 24 mm focal length is nice in viewing the 'bigger picture'. Not quite the 'wide angle' view of my 40 mm plossl, but definitely effective for viewing smaller star clusters. Being able to 'infinitely adjust' the focal length down to 8 mm is considerably easier than changing oculars and having to re-focus, making sure the object being viewed was solidly in the middle of the field of view before zooming in, of course. Images were sharp at the high magnification as well, something I was pleasingly surprised to find. Wish my zoom microscope was as effective. It's a great eyepiece for casual sky viewing with a Newtonian scope; the 'only lens you need' for the most part. The almost-par zoom capability meant little re-focusing adjustment between low (24 mm) and high (8 mm) magnification, so I could quickly explore objects of interest without a lot of need for adjustment. Worked well with the 2X Barlow lens as well, although the light reduction at that magnification with dim objects was very noticeable. Zoom action is a bit stiff; my hope is it's just a built-in 'tightness' as opposed to a lubricant which may become stiffer with winter temperatures. There were no 'click stops' for separate focal lengths, just markings on the outer barrel . . . which isn't a big deal, just an observation. Zooming was always smooth but tight. Solid mechanical arrangement. As is typical for zoom lenses the effective aperture decrease at the higher magnification (8 mm) results in a noticeable dimmng. It was necessary to increase the focal length a bit to be able to still discern a dim spiral nebula in deep space. Viewing the moon was a delight, however, as that is normally so bright a neutral density or double-polarizing filter is necessary to reduce the intensity. Images remained sharp at all focal lengths. Great addition to my accessories . . . but too long to fit into the space I have left in my larger accessories kit. However, don't usually take that with me unless I'm planning a long observation session.

Si bien su precio es elevado, las prestaciones son excelentes. Gracias al zoom evitas el engorroso cambio de oculares durante la observación. Muy recomendable.

Excelente!. Es muy cómodo cambiar de distancia focal sin cambiar de ocular. La imagen es muy clara y nítida. No he notado aberraciones. Soy novato en esto pero hasta el momento he disfrutado mucho este ocular.