I am thoroughly pleased with my purchase of this telescope. Alignment and tracking feature works very well as long as you follow Celestron's tips in the manual. I leveled the tripod and put in the time and my lat and long to give as accurate a location as possible. It has several options for alignment but I find skyalign to be the simplest and quickest. I used skyalign and chose betelgeuse, jupiter and a bright star that I didn't know to align with and I was up and running. I observed Jupiter for over an hour with barely any perceptible drift. The tour function works pretty well, though I recommend a lower power eyepiece to start because it seems that how far away you are from your alignment stars (or planets) has an affect on accuracy. Sometimes it puts objects dead center, sometimes it will be toward a side of the eyepiece. The good news is that you can center it and the scope will continue to track it very accurately allowing you to swap in a more powerful eyepiece. On the topic of eyepieces, the ones that come with the scope feel very cheap. I would describe them as "plasticky". They work decently, but if you have any interest in making amateur astronomy a long term hobby, you will absolutely want to get some new eyepieces and a barlow. I won't fault Celestron for the eyepieces, I planned on buying better ones anyway. My only gripe, and not against the scope itself because it does its job splendidly, is that this scope doesn't come in a 6" or 8" aperture. It was working so well that I got selfish and was yearning to see more. As far as accessories go, you will certainly want a power source that is NOT 8 AA batteries. The AC adapter and an extension cord comes highly recommended. I would also recommend the car cigarette lighter power cord as well if you plan on traveling for darker skies. I considered purchasing a power tank but the majority of reviews have been negative. The RS232 cord might be worth purchasing if you intend to connect your scope to a computer but bear in mind that you will need a USB to RS232 adapter unless you have a decade old computer that you still use. Why they use such a byzantine cable is beyond me. To sum this up, I highly recommend the Nexstar 127 SLT if you have a serious interest in taking up astronomy as a hobby. Operating the scope is a simple task and it provides some very nice views. Just invest in some quality eyepieces and a power adapter.

Nice telephoto lens for the money I had been looking for a while couldn’t afford the others like 2500.00 and up this on does just as good and a lot cheaper

This is simply the best telephoto lens I have ever used. It arrived about 3 weeks ago and has performed flawlessly on both my 30D and my film camera (the old EOS 630). The blurred backround at wider aperture settings is satisfying and seamless, while the contrast, color and sharpness of the image are remarkable. There is a very slight, but barely perceptible, softening of the image on film when the lens is wide open at f=2.8, but by f=3.5 I can't detect any lack of sharpness even on enlargements.The IS works perfectly. There is a little motor noise (very soft) while the IS is engaged, but nothing that would disturb a nearby subject. As others have stated, IS is no complete panacea for hand-held shooting in near total darkness, but I have been able to get a lot of great exposures that would have been impossible with any other telephoto.Another huge plus is that this lens allows full time manual focus; you don't have to flip a switch to override the auto focus. All you need to do is start turning the focus ring. This saves a lot of time and missed shots when the autofocus is choosing something other than what you want to shoot.On the other hand this is not a "walk-around" lens. It is very serviceable off the tripod for short sessions, or even hanging around for a couple of hours. If you watch Art Wolfe on "Journeys To The Edge" (highly recommended show on PBS)he uses this lens a lot, and often hand carries it around without using the neck strap. But it does get heavy after a while. And it is a long,fixed length lens. But the weight and length are just the price we have to pay for a lens that retains its maximum 2.8 aperture through its entire range.If you are serious about the images you create, and can afford the price, this lens is an investment you cannot afford to pass up.

Definitely a good lens, probably use it more than telephoto lenses.

I was in the market for a good small scope that I could use at a moment’s notice with a minimum of fuss and bother and that I could also use as a travel scope without having to baby it. I already own two telescopes (in addition to several binoculars) – a JMI RB-66 on a large alt-az mount (consisting of two 6” reflecting telescopes yoked together and used like a giant binocular) and a Takahashi Sky90 refractor on an equatorial go-to mount. I love both scopes, but the JMI is heavy, cumbersome and a beast to move around. The Sky90 is a lot smaller and lighter, but, when combined with the equatorial mount, it’s still a little too big and heavy to run outside and use on a whim. It was also expensive enough that I’m not comfortable using it as a travel scope where it’s likely to undergo some rough handling. As a result, what I usually found myself doing was grabbing a set of binoculars and using those. There’s nothing wrong with that, except that the image is too shaky to be of much use or to get much enjoyment out of. Enter this scope – at least on paper, the specs were ideal for my needs: It has an aperture of 80mm, which is a good compromise size that should permit decent planetary viewing, lunar viewing, wide-field star viewing (essential for sights such as the Pleiades and certain star clusters) and at least the more prominent individual stars. It’s got a short focal length of 400mm, which makes it more portable and lighter than scopes with a longer focal length. It appeared from the specs to have a stable mount, which is essential for steady viewing. It contains all the accessories necessary to get you started – 3 lenses, a diagonal and a finding scope. And finally, it is being offered at a low enough price that I wouldn’t hesitate to use it as a travel scope. But be aware that this is a compromise size for a telescope. A focal length this short pretty much limits you to lower magnifications. Push the magnification too high and you’ll end up with various optical aberrations, unless you spend a lot of money to get a premium scope that is built to overcome those limitations. This is just a matter of the physics of the situation and it’s going to be a limitation for this sized scope, no matter who makes it. On the other hand, a scope of this size gives you a wider field of view than a scope with a longer focal length and there’s a lot to be said for wide-field telescope viewing. In addition, more aperture is almost always better than less aperture, since the larger the aperture, the more light that will be gathered. However, each small increase in aperture results in much higher prices and much larger sizes. As I said previously, for my purposes, 80mm was a good compromise. There are two other “compromises” in the specs for this particular scope of which the buyer should be aware: First, the diagonal provides an upright image, much like a spotting scope would; and second, the scope uses an alt-az mount, rather than an equatorial mount. But for me, neither of these were a disadvantage. First, if you’re going to be using an alt-az mount and you’re finding targets using star hopping rather than a go-to mount, then it seems to me that using a diagonal with an upright image is easier and more intuitive to use than a reversing-image diagonal. Second, I think that learning to find targets using star charts and star hopping is a good thing to do and I think that it is easier to do that using an alt-az mount rather than an equatorial mount. Now, on to how this particular scope performed in real life: Unpacking: When I received the shipping box, it looked like it had gone through some pretty rough handling on the way from the seller to me. However, when I opened everything up, it was clear that it had been well cushioned and there was no damage to anything that I could see. Assembly: The only instructions are contained on a laminated picture board that details the steps necessary for assembly. However, the only thing you really have to do is to fit the already assembled optical tube assembly, finder scope and diagonal to the mount. Other than that, everything is already assembled. The only caution I would give you involves the finder scope. In addition to two collimating screws, there’s also a metal spring button that helps to secure the finder scope within its own small tube (which is then attached to the main scope). This metal spring button comes in four small pieces – a small metal canister which is already screwed into the finder-holder tube, a small metal spring, a second canister which slides into the first, and a small screw which holds everything together. In my package, the spring, second canister and screw were all loose in the packaging, so make sure you don’t throw anything away until you’ve found them and assembled them properly. The instructions don’t tell you how to assemble them but when you look at the pictures and see what the purpose of the spring button is you’ll find that there’s only one way that it all works. The second thing to note about the finder scope is that there should be a rubber O-ring near the objective lens side of the finder scope. This O-ring fits in a groove on the finder scope and when the finder scope is inserted into its holder, it needs to be pushed in far enough that this O-ring actually fits inside the holder. This is an important step, because it ensures that the finder scope is securely held in its holder and doesn’t slide around. I saw a You Tube review that complained about a loose finder scope on this scope and it was clear that he had not followed this step, which was the cause of his problem Calibrating the finder scope: In daylight, take the assembled scope outside and insert your lowest powered eyepiece into the diagonal (that’s the 25mm eyepiece). Then aim the scope at a far-away object, center that object in the scope and focus the scope. Then, look through the finder scope. Before you do anything else, focus the finder scope until you get a sharp image of whatever it’s pointed at. You do that by twisting the front barrel of the finder scope. Once it’s focused, turn each set screw in the finder scope separately until the same object that is in the center of your main viewing lens appears in the X crosshairs of the finder scope. If you want to fine-tune it, replace the lens with a higher magnification lens and reset the finder scope. At this point, the finder scope should be good enough to use for the first time. When you use it for the first time at night, you can then calibrate it one more time and, at that point, you shouldn’t have to fiddle with it anymore. I didn’t expect anything special from this finder scope and thought that I would probably have to replace it. I was wrong. It is not flimsy, it appears to have good optics, it is stable and it does exactly what it should do – it enables you to easily find and center your scope on the intended target and then tighten down the telescope so that you can switch to your main eyepiece and be confident that your target will be in the center of your field of view. The quality of the finder scope was a pleasant surprise. The mount: From the pictures online and the specs, the mount certainly seemed sturdy, but the proof is in the pudding – is it sturdy and heavy enough to be stable, does it move smoothly and can it be locked down effectively so that it doesn’t drift? The answer is yes to all three questions. Bear in mind that the scope itself is very light. There is no need to use counterweights with this scope. In any event, the mount was rock solid. It didn’t tremble and it didn’t shake. The legs lock absolutely securely after they’re extended. The mount moves the scope smoothly in all directions and then locks down tight when you’ve centered your target. This is a quality mount. The eyepieces: There is both good news and bad news about the eyepieces (including the 3X Barlow lens). The lowest magnification eyepiece (the 25mm) and the middle magnification eyepiece (the 10mm) both performed fine. Good focus was easily achieved and the view appeared sharp enough for my purposes from edge to edge. The highest magnification eyepiece (the 5mm) was a piece of junk. Even in daylight, views were fuzzy. Using it to look at the moon, or Jupiter, or stars was a waste of time. It would simply not come into focus, no matter what I did. Maybe this was just bad luck with the particular eyepiece that I received, but I won’t be using it. However, another pleasant surprise for me with this scope was the 3X Barlow lens that came with the scope. It is a short lens and it’s entirely made of plastic so that it appears to be pretty flimsy. I’m not a big fan of Barlow lenses to begin with and I didn’t have high hopes for this one. However, when I found that the 5mm eyepiece was useless, I decided to go ahead and try the Barlow lens. Much to my surprise, it not only worked, it worked pretty darn well. Like all Barlow lenses, it darkens the image and it simply magnifies whatever image you’re already receiving with the underlying eyepiece – it doesn’t improve that image. But if you want higher magnification than the 40X provided by the 10mm eyepiece, you can either buy a new eyepiece or you can use the Barlow lens. This Barlow lens is good enough to give you both options. The optical tube assembly (the “OTA”): This is the heart of the scope. I ran it through four tests: First, when I was calibrating the finder scope, I also looked to see how the OTA performed. Second, I used the scope shortly after dusk. While there was some cloud cover and we were expecting rain later that evening, there was a clear view of Jupiter and also of a bright star, Arcturus. But because of high humidity, viewing conditions were not ideal. Third, I got up at 3:30 in the morning and went back out again. By this time, Jupiter was no longer visible, but the half-moon was clearly visible and there were also a large number of stars visible. Between my first viewing and the second one, we had had a good rain, which seemed to clear some of the humidity from the air, resulting in better viewing conditions. Finally, this morning, I used a collimating eyepiece to check the collimation of the OTA. Daylight views were fine, but they’re not much of a test for an astronomical telescope. Suffice it to say that the views were clear and well-focused (except when I used the 5mm eyepiece). My first views of the evening were also good. Using the medium eyepiece (10mm – 40X), I could clearly focus and see Jupiter and four of its moons. I was also able to clearly see two equatorial bands on Jupiter. Clarity was good but not exceptional, probably due to the high humidity. Arcturus resolved clearly. I did not see any color or other aberrations and the view using the two lower-powered eyepieces appeared to be sharp from edge to edge. Just for fun, I also used one of my own wide-field eyepieces, a 40mm eyepiece. It gave a spectacular wide-field view of the stars. That use of the scope is clearly one of its strengths. Finally, I did a rough collimation check by moving the scope slightly out of focus to see if the image remained round and without distortion. It did, suggesting to me that the tube was properly collimated (more on that later). My views later in the evening were even better. The details on the moon were sharp with no color or other aberrations in the view and the stars appropriately resolved to single points of light. I did the same rough collimation check as I did earlier and the results appeared to confirm my original impression that the scope was well collimated. The one point I should mention from both of my evening views is that the contrast is less in this scope than it is in my Takahashi. The Takahashi is a much more expensive scope and the lens coating and scope baffling is top-rate, so the comparison may not be a fair one. Moreover, the contrast in this Chinese-made scope (and most scopes today are probably made in China, even the most well-known brands sold in America) was perfectly fine and didn’t detract from my use or enjoyment of this scope. The buyer should just be aware that he or she shouldn’t expect the same deep contrast you get with more expensive scopes. Finally, after daylight, I used a collimating eyepiece from Orion to check out the collimation of the scope. I’m no expert, but it certainly appeared to me from that test that the scope is spot-on in its collimation. Bottom line conclusions: For my purposes, this is a great scope for the price. It is small and portable (I could easily move the entire scope and mount from place to place using only one hand). It performs very well indeed when used for wide-field views at lower magnifications, but still permits excellent lunar viewing and good planetary viewing. The acid test for me would be to see whether it clearly resolved double stars. I didn’t have the opportunity to try this last night. If and when I do try it with this scope, I’ll try to remember to come back and edit this review to add those results. But I expect that that might prove a challenge for this scope because of the higher magnifications normally required to clearly split doubles. In any event, if you require higher magnifications, you should probably be looking for a different type of scope altogether, but you’ll probably need a much larger and more expensive scope than this one. Also, because this scope doesn’t come with an equatorial mount or a motorized mount, don’t expect to use it for astrophotography. But for a small, portable scope with enough aperture to offer a large number of different viewing experiences, this scope was perfect for my needs. I highly recommend it. I received this scope at a discount for my honest opinion.

I'm giving this 4 stars - 5 stars for what it does, and 3 stars for the fiddly.I use a Panasonic Lumix G6 MFT camera, and use full-size DSLR lenses with adapters for telephoto along with the occasional adapter that doubles the focal length of the kit lens. Hey, I'm on a budget!The Booster absolutely performs as advertised. When I first got it, I noticed that it was, well, *plasticky* and didn't feel very strong. It came with two adapters for the hot shoe (which I promptly misplaced but found again), and full directions. It took a bit of fiddling with the shoe mounts to get it seated correctly on the camera. I found that the only way to get it to perform properly was with one of the shoe adapters. With an adapter and the Booster in place, miracles happen.Everybody knows that the pop-up flash that every camera comes with is pretty much crap. Well, this little item with the War of the Worlds looking fresnel lens solves a lot of the issues.This will not work with your regular kit lens. This is meant for telephoto distance shooting, and that's how it best performs. Anything shorter than telephoto means that you'll have a blown out white circle in the middle of your picture! Ask me how I know...The pros of this item are pretty simple: It gives your pathetic pop-up enough power to brighten telephoto pics. After the fiddly part is done, it works perfectly. And it's made in the USA. Boom.The cons are simple, too: Plasticky feel, but may be stronger than it seems. It works on telephoto and ONLY on telephoto. Wish that they'd make one for wide angle!So to sum it up, I'm completely happy with the device and like the way it works. I just wish that the fit and finish would give me a little more confidence in its longevity. If it lasts, I will update it to five stars.

i love this combo. the lens's give me everything I need to shoot. kinda wish i had a telephoto but this works for now! thanks canon

Assembling is as easy as placing lens on eyepiece and tightening with fingers.