The Optical Tube
The Celestron StarSense Explorer 12” Dobsonian is a Newtonian-reflecting telescope. As the name would suggest, it features a 12″ (305mm) primary mirror with a focal ratio of f/4.9 and a resulting focal length of 1500mm, which exceeds the focal length of standard 6″, 8″, and 10″ Dobsonians, which are generally available with the same focal length of 1200mm. The cost of manufacturing a 12” f/4 or f/4.5 mirror would be significantly higher, and it is less compatible with less expensive eyepieces, which is why commercially available 12” Dobsonians tend to be around f/5.
The choice of a slower f/4.9 mirror minimizes the impact of coma that may appear at the edge of low-power eyepieces’ field, and less expensive wide-angle eyepiece designs like Erfle, SuperView, and “SWA” oculars still manage to produce pleasing images unless scrutinized closely around the edges of the field.
The primary mirror of the StarSense Explorer 12″ is mounted on a 9-point flotation cell to prevent any distortion of the mirror under its own weight, and it can be adjusted (collimated) without the need for any tools. While the cell does adequately support the mirror, its too-weak springs can sag, causing the telescope to go out of collimation if you don’t replace the stock springs or overly tighten the locking knobs on the cell, which you can actually remove if you upgrade to stiffer collimation springs. Replacement, stronger springs can be found at any hardware store for a few bucks and installed in a few minutes.
Adjusting the StarSense Explorer 12” Dobsonian’s secondary mirror requires a hex key, but you’ll rarely need to do so. Resist the urge to replace the hex keys with thumbscrews; they tend to loosen over time and necessitate frequent readjustments.
Collimating any Newtonian reflector may seem intimidating or complex, but there’s no need to fret. Though it might be a bit confusing initially, the process of collimation isn’t overly difficult or time-consuming, and the StarSense Explorer 12″ typically maintains its collimation between uses, even when transported. However, you might want a more accurate tool than the included collimation cap due to the stringent tolerances at f/4.9 compared to a slower telescope.
The StarSense Explorer 12” Dobsonian is nominally capable of handling magnifications up to 600x thanks to its sharp optics and large aperture. However, atmospheric conditions, as well as the telescope itself, are likely to limit you more often to less than half of that. Unlike some of its competitors, this scope lacks a built-in cooling fan, though it’s fairly easy to add one, and threaded holes are provided at the back of the mirror cell for mounting a fan.
The single-speed 2″ Crayford focuser on the StarSense Explorer 12″ Dobsonian is identical to those found on many Orion and Sky-Watcher Dobsonians. It uses thumb screws to secure your eyepieces, and reaching focus with most eyepieces requires a 2″ extension tube (included). The provided 1.25″ adapter, thankfully, includes a compression ring and is threaded for 2″ filters at the bottom. Unlike Sky-Watcher’s Dobsonian range, these scopes bypass the issue of separate 1.25″ and 2″ extension tubes.
The tube of the StarSense Explorer 12” Dobsonian is furnished with the same knob and carry handle as the smaller StarSense Explorer Dobsonian telescopes. While it’s a nice thought, in practice, you might need an additional lifting strap or handle installed to adequately grip the scope, and the tube is so wide that you rarely end up using the knob at the end anyway.
The Celestron StarSense Explorer 12″ Dobsonian comes with a single 25mm, 1.25” Plossl eyepiece, which provides 60x magnification. With a 52° apparent field of view, this translates to a true field of about 0.9°, or a little under twice the angular diameter of the sun or moon in the sky—not terribly wide but not too narrow either. This eyepiece is a decent starting point, but you’ll quickly realize the need for additional eyepieces of varying focal lengths to achieve a range of magnifications. For instance, a high-power eyepiece is essential for observing the moon and planets, while a 2″ wide-angle eyepiece can provide sweeping views of deep-sky objects. These are just a couple of examples of the types of eyepieces that will likely be immediately useful.
A collimation cap is provided with the StarSense Explorer 12” Dobsonian to assist you in aligning the optics. While not as precise as a fancy metal Cheshire, it will do the job. Check out our collimation guide for more information on collimation tools and how to use them.
The StarSense Explorer 12” Dobsonian also comes with a standard red dot finder. This accessory allows you to manually aim the telescope when you’re not using the StarSense Explorer app or phone dock.
The mount of the Celestron StarSense Explorer 12″ Dobsonian is of the Dobsonian design, quite akin to those from other manufacturers—specifically those made by Sky-Watcher and older Orion products from the same OEM, Synta. In line with the classic Dobsonian style, it’s an alt-azimuth design that relies on plastic pads for smooth left/right (azimuth) and up/down (altitude) motions, leveraging friction to eliminate the need for gears or locks.
The StarSense Explorer 12” Dobsonian’s motion is dictated by a pair of altitude bearings resting on plastic rollers fixed inside the rocker box. The scope seamlessly drops onto these bearings, and brake/clutch knobs on either side can be slid into slots in the rocker to adjust the friction for the up-and-down motion of the scope. This system is a slightly refined version of the one implemented by Sky-Watcher in many of their Dobsonian designs.
Due to the small size of the altitude bearings on the StarSense Explorer 12”, they tend to be overly sensitive to pressure, hence why Celestron included a clutch knob to generate friction by pressing them against the rocker box’s sides. However, the small size of the bearings means that balance issues are inevitable with heavy accessories.
When a heavy eyepiece or additional accessory is mounted on the StarSense 12” Dobsonian’s front end, the entire device tends to gradually tip over due to being top-heavy, especially when it is aimed lower in the sky. The additional weight at the top shifts the scope’s center of gravity outside the altitude bearings. Tightening the clutch may prevent the scope from moving up and down of its own accord, but it inevitably hampers your ability to smoothly aim and track the telescope across the sky, unlike other solutions implemented by manufacturers such as sliding the bearings along the tube to compensate for center-of-mass shifts or using spring-tensioning to create a larger virtual bearing.
Constructed entirely from particle board, the StarSense Explorer 12″ Dobsonian’s mount isn’t built for prolonged durability or resilience. This may not necessarily be a problem since a dented or slightly warped mount due to moisture exposure can still function. Should the need arise, creating a new and improved base from plywood is relatively simple and inexpensive; it could also reduce weight, and bigger bearings could be added to lessen balance issues.
Celestron’s StarSense Explorer Technology
Operating the free Celestron StarSense Explorer app and setting up the phone dock attached to the 12” Dobsonian is straightforward. Following a brief alignment process, the app aids in locating thousands of deep-sky objects. It does so by tracking and indicating where your scope is aimed at in real-time, utilizing your phone’s camera and gyroscope data. The level of accuracy depends largely on your smartphone’s quality but can be as precise as approximately a quarter of a degree, or half the full moon’s width. Celestron has enhanced and updated the app for their Dobsonian telescopes, furnishing it with a significantly larger database than before. The previous, smaller database had rendered the StarSense Explorer technology somewhat ineffective for locating anything beyond the most conspicuous and bright targets.
The StarSense Explorer system is limited to an accuracy of a bit better than 0.25 degrees, or half the width of a full moon. This is much less precise than a real GoTo system or encoder-based digital setting circles, but more than accurate enough for locating most deep-sky objects.
Should I buy a Used Celestron StarSense Explorer 12″ Dobsonian?
The Celestron StarSense Explorer 12″ Dobsonian is a relatively new product. As such, it’s unlikely you’ll find a used one at the moment unless it was bought and never used outside. There simply hasn’t been sufficient time for many of these telescopes to endure neglect or damage. Nonetheless, the standard advice still applies: inspect for any damage to the base or mirror coatings. Cosmetic damages or minor dents on the tube are generally tolerable. A damaged base can be replaced, but it may require a bit of carpentry skills or a considerable amount for a custom-made one.
Alternative Recommendations (USA)
The Celestron StarSense Explorer 12” Dobsonian is more portable but less well equipped than its immediate competitor, the 12” GSO Deluxe Dobsonian, sold by Apertura, Zhumell, and Orion as the AD12/Z12/SkyLine 12, respectively. You might also want to consider a truss tube or a smaller computerized telescope. Here are some options we’ve picked out:
- The Apertura AD12/Zhumell Z12/Orion SkyLine 12 features similar optics to the StarSense Explorer 12” Dobsonian but includes features like a dual-speed Crayford focuser and a pair of quality eyepieces, as well as a fan, which the StarSense Explorer Dobsonians lack. However, the AD12/Z12 base is considerably inferior to and heavier than that of the StarSense Explorer 12″, and the scope must, of course, be entirely manually aimed with its 9×50 finder scope.
- The Apertura AD10, Zhumell Z10, and Orion SkyLine 10 share numerous characteristics and accessories with their larger siblings, the AD12 and Z12. However, they come in a markedly smaller design that favors portability. A 10″ telescope is significantly less costly than a 12″ version, freeing up your budget for additional accessories or trips to dark-sky locations, which could potentially compensate for any performance differences.
- The Celestron StarSense Explorer 10″ Dobsonian is somewhat less hefty than the AD10/Z10, and it incorporates Celestron’s proprietary StarSense Explorer technology and a lightweight base like the 12” model.
- The Explore Scientific 10″ Hybrid Dobsonian stands out for its extreme compactness thanks to its truss tube design. The design also facilitates straightforward collimation adjustments for the primary mirror. Nevertheless, the telescope is notably deficient in accessories, necessitating further investment and enhancements before you can fully enjoy its functionality.
- The Sky-Watcher 12″ FlexTube Collapsible Dobsonian employs a collapsible FlexTube design that condenses the tube length sufficiently to fit within a regular vehicle. It also includes a simple yet suitable accessory kit to get you started. Although it’s not as compact as the Explore Scientific or Orion truss tube scopes, it’s significantly simpler to assemble.
- The Explore Scientific 12″ Truss Tube Dobsonian is equipped with a high-grade dual-speed Crayford focuser and has an optimized, compact all-metal structure when disassembled. Its manual movements are exceptionally fluid and precise. However, it lacks useful accessories like eyepieces or a finder and requires additional components, such as a shroud to function optimally.
- The Orion SkyQuest XX12i Dobsonian features a condensed shape that is similar to the Explore Scientific 12″ Truss due to its truss construction. However, both its upper and lower assemblies are taller, and the base is substantially more cumbersome. Orion’s bundled IntelliScope encoders can assist you in locating deep-sky objects, although the system isn’t as user-friendly or quick to set up as the Celestron StarSense Explorer, which is regrettably not available with a 12″ Dobsonian option at the moment.
- The Sky-Watcher 10″ FlexTube GoTo Dobsonian offers full motorized GoTo and tracking functions in a design that is more compact compared to the manual 10″ and 12″ FlexTube scopes. More recent models support remote control through your smartphone or tablet, and you can manually aim the telescope without affecting its GoTo and tracking capabilities.
- The Orion SkyQuest XT10G Dobsonian provides comprehensive motorized tracking and GoTo functionalities while also allowing for manual aim. It retains the same general functionalities as the Sky-Watcher 10” FlexTube but enhances user experience with a dual-speed focuser and a simpler, solid tube design.
- The Celestron NexStar Evolution 8, although it gathers and resolves less light than a 10″ or 12″ Dobsonian, is exceedingly compact and includes an integrated battery. Additionally, it comes with comprehensive motorized tracking and pointing capabilities, controllable through your smartphone or tablet.
Aftermarket Accessory Recommendations
For optimal use of the Celestron StarSense Explorer 12″ Dobsonian, consider securing a few high-quality eyepieces for both low and high powers. You might find a 30mm or 24mm Explore Scientific 82-degree (providing 51x or 64x magnification, respectively) or a Meade 28mm PWA (yielding 55x) an excellent choice for expansive, low-power views. Supplementing these with a 12–16mm eyepiece, like the Meade 16mm PWA, 16mm Nagler Type 6 (95x), 13mm Nagler (117x), or 14mm Explore Scientific 82-degree (109x), should effectively cover your medium-power requirements.
Medium to high magnification with the StarSense Explorer 12″ is elegantly handled by a 9mm goldline/redline (offering 169x magnification). If you have a bit larger of a budget, the 8.5mm Explore Scientific 82-degree (providing 179x) promises broader and sharper visuals. Depending on how favorable your atmospheric conditions tend to be locally, it might be beneficial to consider additional eyepieces for up to 300–500x, such as the 6.5mm and 4.5mm ES82 LER eyepieces (yielding 235x and 339x magnification, respectively), or similar short focal length, high-quality, wide-field oculars. However, bear in mind that with this scope, magnifications above 300x might not frequently provide optimal viewing, as minor atmospheric disruptions can compromise image clarity at such high power.
For precise collimation and crisp visuals, you might be better off spending the money on a good laser collimator or Cheshire, which is more precise than the collimation cap provided with this telescope. Furthermore, you might want to contemplate acquiring a coma corrector, such as the Explore Scientific HRCC, Baader MPCC, or Tele-Vue Paracorr II. Although these devices can be rather pricey, they offer clear, edge-to-edge views of the stars when used with this telescope and a high-quality wide-angle eyepiece.
Lastly, a narrowband Ultra High Contrast (UHC)/OIII nebula filter can significantly enhance your viewing experience of many nebulae, like the Orion Nebula, when used with virtually any telescope, including the StarSense Explorer 12″ Dobsonian. This filter also amplifies the visibility of planetary nebulae by reducing the apparent brightness of stars through the eyepiece without diminishing that of the nebula, thereby increasing contrast and facilitating their location at low power against a dense backdrop of stars. Additionally, it offers enough contrast improvement to unveil details in objects that might have previously been entirely invisible, such as the Veil Nebula or Flame Nebula. These are just a few examples of what can be observed with the StarSense Explorer 12″ Dobsonian under appropriately dark skies.
What can you see with the Celestron StarSense Explorer 12″ Dobsonian?
The Celestron StarSense Explorer 12″ Dobsonian, with its significant aperture, is a superb choice for deep-sky observations. Under unpolluted, dark skies, it will enable the viewing of thousands of galaxies, highlighting details such as spiral arms and dust lanes in galaxies like M51 and M82, individual stars in the Andromeda Galaxy, and even extragalactic globular clusters. However, the allure of galaxies might be diminished under light-polluted conditions, appearing more like faint smudges. This underscores the benefit of the StarSense Explorer 12″ Dobsonian’s portability, making it an ideal companion for stargazing under dark, clear skies far from city lights.
This telescope also excellently unveils details in a variety of planetary nebulae, rendering vibrant colors and intricate patterns. Even in the light-polluted city or suburban skies, the brilliance of these nebulae is undiminished. Some, like the Blinking Planetary Nebula, even exhibit visible white dwarfs at their centers. Emission nebulae such as Orion and the Lagoon Nebula take on an exceptional visual appeal with the StarSense Explorer 12″, especially under dark skies and when paired with a UHC filter. On exceptional nights, the elusive Pillars of Creation within the Eagle Nebula, M16, might just become discernible. Furthermore, the StarSense Explorer 12″ provides opportunities to resolve globular star clusters like M13 and M15 into individual stars at high magnification. You’ll also enjoy viewing numerous open star clusters showcasing vibrant stars, even under city-lit skies.
Observing the Moon and planets becomes a visually stunning experience with a high-quality 12″ Dobsonian like the StarSense Explorer. Expect to distinguish the phases of Mercury and Venus, Mars’ ice caps, dark markings, and countless lunar details. Jupiter’s cloud belts and Great Red Spot are present in a striking fashion, and the disks of its moons become clearly discernible when atmospheric conditions allow, along with their shadows during transits and even some features on Ganymede and Io. The spectacle of Saturn’s rings and the Cassini Division within them is breathtaking, and under ideal conditions, even the Encke Gap within the rings is observable. Saturn’s cloud bands and a blue-gray polar region, housing the planet’s hexagonal polar storms, are visible. Approximately half a dozen of Saturn’s moons can be spotted around the ringed planet, with Titan appearing larger than a mere point source, presenting a golden-yellow color.
Under the best viewing conditions, Uranus’ greenish disk might reveal faint cloud markings, and its four brightest moons—Ariel, Umbriel, Oberon, and Titania—emerge faintly with the 12″ Dobsonian. Neptune, although half the angular size and dimmer than Uranus, is clearly seen as a bluish disk, and its largest moon, Triton, is more noticeable than Uranus’ moons due to its larger size and more reflective surface. Pluto can also be detected as a dim, star-like point under dark skies using a telescope with this aperture.
While it is possible to carry the StarSense Explorer 12” Dobsonian (as the tube weighs only about 50 lbs and the base is less than 40), the tube is about the size of a short adult human. It is awkward to carry, no matter what you do. Thus, moving it over any considerable distance without wheels is not recommended. It should also be noted that with a 5-foot (1.5 meter) long tube and a base about as wide as a typical office chair, you need a large vehicle to transport this telescope to dark skies or on any other excursions.
For quick at-home transportation and setup, you could consider placing the scope on a dolly or something similar like JMI’s Wheely Bars, but cheaper dollies can cause the mirrors to lose collimation due to vibrations, and the latter can be bulky to store and expensive. Furthermore, these options typically remain attached to the telescope during use, which may position the eyepiece too high for shorter users, especially when the scope is aimed vertically. These options work best if the scope is only moved from a garage or shed across paved surfaces and the added height is not a concern.
The ideal solution for a quick, cheap, and easy way to roll the scope around seems to be strapping the StarSense Explorer 12” Dobsonian to a hand truck and using padding to prevent scuffing the tube. This is cheaper, easier to store, and more maneuverable than a dolly. If you’re lucky enough to have good skies right outside your door or garage, the StarSense Explorer 12″ can be stored on a hand truck, ready to be used at a moment’s notice. It’s as convenient as a much smaller scope. It’s also quite straightforward to tip it into a vehicle off the hand truck. Pneumatic tires will prevent uneven terrain from loosening the collimation knobs/screws on the scope’s optics. If transporting the telescope in a car, be sure to detach the optical tube from the base after you load it up.
Like all Dobsonians, the StarSense Explorer 12″ is too large and cumbersome for a carrying case or bag, though nonetheless, somebody will try to sell you one. Wrapping the tube in a blanket or towel suffices, and the base should ideally be transported upright, resting on its feet The foam from the shipping box can be used to secure the scope in a car and brace it against a hand truck if need be.