Celestron StarSense Explorer DX Optical Tube Assemblies
The StarSense Explorer DX comes in two varieties: A 130mm Newtonian reflector and a 102mm refractor, being f/5 and f/6.5 respectively. They are carbon copies of many of Celestron’s other scopes.
At 650mm focal length and having very similar light-gathering capability due the slightly higher efficiency of the refractor, both the DX 102 and 130 have identical fields of view and basically the same views – the only difference is the more normal orientation and slight chromatic aberration seen through the refractor. The Newtonian should in theory slightly outperform the refractor (and lacks chromatic aberration), but in practice I would say there is really no difference between the scopes. The prices are almost the same, so I think it really comes down to personal preference. I myself lean towards the refractor.
The focusers on both scopes are rack-and-pinion designs, and technically 2”. Unfortunately, the DX 130 has a weirdly-sized 2.5” focuser with no direct 2” attachment, and the DX 102 cannot actually balance on its mount with a 2” diagonal and eyepiece, so in practice they are both limited to 1.25” eyepieces/accessories only. Thankfully, even with 1.25” eyepieces you can squeeze out a field of view of about 2.5 degrees with a 32mm Plossl or similar in either scope, so this should not be of a huge concern to a beginner.
About the StarSense Explorer DX Mount
The StarSense Explorer DX mount is nothing more than a repainted Omni XLT AZ mount with a bracket for the StarSense Explorer device. This mount is a little on the small side for either optical tube, but it works just fine. It’s a simple, aluminum-legged alt-azimuth mount with slow-motion controls on both axes. The accessory tray is a nice, sturdy affair and an actual tray rather than the silly eyepiece rack supplied with many scopes (which I have never understood the point of, it’s just a great way to get your eyepieces damaged and have them dew up faster).
One minor complaint about the mount, and one that bothered me especially with my sample: You cannot adjust the tension/friction on either axis without a socket wrench, and even then it is very difficult. My mount came EXTREMELY overtightened to the point that you could not actually move the scope in altitude, and it took me a fair bit of strength, some disassembly of the mount and overall around half an hour of work to fix. Adjusting the azimuth axis involves just popping off a small plastic cover on the center of the mount and loosening/tightening the lock nut as needed with a socket wrench/screwdriver.
Reviewing the Accessories
The StarSense Explorer DX scopes both come with two eyepieces: a 25mm Kellner providing 26x and a 10mm Kellner providing 65x. They are by far the weakest links in the scope. The coatings seem to be of very low quality, the whole build is plastic, and the eyepieces have lots of internal reflections and ghosting that are very evident on the Moon, planets, and bright stars. They would be fine for a sub-$200 telescope but for the price Celestron is asking for the DX scopes I would really like it if they provided even slightly better eyepieces.
Both telescopes come with Celestron’s standard “StarPointer” red dot finder which you see on pretty much all beginner telescopes these days. It is actually somewhat redundant with the StarSense Explorer technology, but I appreciate its inclusion.
The DX 102, being a refractor, of course comes with a star diagonal – Celestron’s standard, nearly all-plastic Amici prism diagonal. It works fine and provides a correct left-right/up-down view, but vignettes with any eyepieces with a wider field stop than the stock 25mm Kellner, has annoying diffraction spikes on bright stars, and seems to suffer from internal reflection and ghosting problems of its own. I would recommend replacing it once you’ve taken care of the eyepiece situation.
The StarSense Explorer Technology
The StarSense Explorer at its core actually uses a relatively old technology known as plate-solving. In essence, what it does is take a snapshot of the sky, and uses computer algorithms and star maps to figure out where it is pointing. Normally, this is done for astrophotography to avoid performing a time-consuming GoTo alignment, and is only used to find one target.
In principle, the StarSense Explorer tech is basically a bracket to point your phone at a small mirror which has been aligned to the telescope mount, then uses the phone’s onboard camera and processing power to plate-solve.
Thanks to your phone’s limited battery life and computing power, the StarSense Explorer tech obviously can’t take a new picture of the sky every time you move the telescope. It would kill your phone quite fast. Instead, it uses plate-solving technology occasionally when you first set up the telescope or move it across a significant portion of the sky, then tries its best to extrapolate finer movements using your phone’s relatively inaccurate gyroscopes and accelerometer. In practice, this system is limited to an accuracy of about 0.25 degrees – or half the width of a full Moon – much less precise than a real GoTo system with tracking, but much simpler, easier and more reliable than a motorized telescope.
The StarSense Explorer App & Interface
The StarSense Explorer app is stupidly easy to set up. All you need to do is install the app, enter the unlock code that came with your telescope, and dock the phone to your telescope. The bracket fits most phones, and will work just fine even if you have a relatively thick case (or even a PopSocket, which I was shocked by). Once you undergo a super-simple alignment procedure, the StarSense Explorer app has a couple hundred objects it can find for you – the Moon, planets, most of the Messier catalog, and some of the brighter NGC/Caldwell objects. I would’ve appreciated the addition of maybe a few hundred additional NGCs and some double stars, but the included catalog is sufficient for a beginner and Celestron could always expand it later. Overall I like it for what it does.
Many people have asked on astronomy forums and contacted Celestron themselves asking why the bracket and code cannot be sold as a stand-alone item. Celestron’s main explanation is that many beginners would buy the bracket and attempt to fit it onto substandard telescopes (or simply do it improperly) and become frustrated. I agree with this sentiment, but additionally I think the technology would simply be of little use on a large Dobsonian or high-end altazimuth mount. It is not accurate enough to be useful for a really big scope and the catalog is too sparse anyway.
Overall, while it would not always be my first choice the Celestron StarSense Explorer DX is definitely one of my favorite beginner scopes in its price range. I definitely recommend either model, especially if you plan on complementing the scope with something larger later on. However, do give some of our other recommendations like the Skywatcher 8″ Dob and Celestron Astro-Fi 130 some thought before making a final verdict.