The C6N Optical Tube
The Celestron Advanced VX 6″ Newtonian’s optical tube assembly is a 6” (150mm) f/5 Newtonian reflector, which has a focal length of 750mm. This is similar in specs to many imaging Newtonian astrographs out there, along with 6” f/5 tabletop Dobsonians. As is typical for these scopes, the optics in the Advanced VX 6” Newtonian are quite good, and at f/5, coma is barely visible at the edges of the field of a 1.25” eyepiece, though cheaper wide-angle eyepieces will have other aberrations at low powers away from the center of the field.
The Celestron Advanced VX 6” Newtonian uses a simple 1.25” rack-and-pinion focuser (albeit one made of metal and not plastic, at the very least). For visual use, a 1.25” focuser limits the achievable field of view. For astrophotography, a single-speed, cheaply-made rack-and-pinion focuser is insufficient to hold a heavy camera, and the 1.25” diameter prevents the use of a coma corrector to achieve sharp stars across the field of view as well as causing vignetting with larger camera sensors. You can retrofit a new focuser onto the C6N, but such an upgrade can easily cost several hundred dollars, and for imaging use, this induces worries about correct positioning and tilt if you do the installation yourself. The 1.25” adapter on the focuser unscrews to reveal standard T-threads to attach a DSLR or mirrorless camera, but as we mentioned, this is not ideal due to the focuser being prone to sagging or slipping out of focus under a heavy load and lacking any fine adjustment capabilities.
Collimation of the C6N optical tube is achieved through the use of three collimation screws on the back of the primary mirror cell and three hex screws on the secondary mirror holder, allowing you to adjust the alignment of the mirrors as needed. You’ll need a collimation tool, sold separately, to accurately collimate the C6N, since one is not included with the telescope by default.
The C6N attaches to the Advanced VX mount with a pair of tube rings, which allow for rotation of the tube as well as sliding it for balance, bolted to a Vixen-style dovetail plate that can be interchanged onto a variety of different equatorial and alt-azimuth mounts.
Like most Celestron computerized telescopes, the Advanced VX 6” Newtonian includes only one eyepiece, a 25mm Plossl providing 30x with the C6N optical tube and with a roughly 52-degree apparent field of view, which translates to a true field of 1.75 degrees across in the sky, or 5.5 times the angular diameter of the full Moon. While the 25mm Plossl does not max out the true field of the C6N, it is pretty close and is a decent ocular for low-power views of deep-sky objects. Additional eyepieces are necessary for higher magnifications.
The only other accessory provided with the Advanced VX 6” Newtonian is a 6×30 finder scope, which shows stars a couple of magnitudes fainter than the unaided eye and has an upside-down 7-degree field of view (similar to 7×50 binoculars) and crosshairs. It is adequate for the task .
The Advanced VX Equatorial Mount
The Advanced VX mount is Celestron’s low-cost GoTo computerized German equatorial mount. It is priced lower than competitors with a higher weight capacity, but makes compromises in its quality in order to achieve this. The biggest of these compromises is the use of cheap servo motors in the Advanced VX. Servo motors provide less precise tracking and guiding capabilities than stepper motors found in most other mounts, which can be problematic for deep-sky imaging. The Sky-Watcher HEQ5 Pro, EQ6R Pro, and various mounts from iOptron are vastly superior for deep-sky astrophotography purposes compared to the Advanced VX.
The other mechanical and technical aspects of the Advanced VX mount are also noticeably inferior to more expensive designs; the declination shaft is improperly supported by its bearing, and the mount saddle accepts Vixen and CGE-style dovetail plates but is a hair too narrow to support a true Losmandy D-style plate (millimeters wider than the CGE design) and grips dovetails with a simple pair of screws that dig into the metal and do not provide as secure a grip as a clamping design. Interfacing with the Advanced VX via a PC can be done with ASCOM drivers, but the mount requires you to use a MicroUSB cable and connect via the hand controller, rather than directly to the mount with a cable. This means that the Advanced VX also does not support EQMOD software and requires you to autoguide through its own ST-4 port rather than via a PC connection due to its lack of software support. Celestron also neglects to include a polar scope for polar aligning the mount by default in order to keep the retail price as low as possible.
In spite of its flaws, the Advanced VX can still work fairly well if you take its limitations into account. The 6” f/5 C6N optical tube is a fairly hefty payload for the Advanced VX to handle, at about 12 lbs bare, rising to 15 lbs with a camera and guiding equipment attached. However, if you don’t take overly long exposures and can achieve a good polar alignment, you should be fine.
Apart from the additional steps of balancing and polar alignment, the Advanced VX handles a lot like Celestron’s cheaper alt-azimuth GoTo mounts, using the same NexStar+ hand controller should you not elect to operate it through your PC. The C6N attaches to the dovetail saddle and balances with a single 11 lb counterweight, though barely, so you’ll need an additional weight or counterweight shaft extension for imaging purposes. Polar alignment can be accomplished with Celestron’s All-Star Polar Align, a polar scope, or a tool such as the PoleMaster.
Once polar alignment is complete, you simply go through a 3-star alignment, and the Advanced VX will then automatically slew to and track anything in its 40,000 object database. Features such as a sync tool and PPEC are available to improve tracking and GoTo accuracy for visual use throughout an observation session if inaccuracies build up.
The Advanced VX accepts Celestron accessories such as the SkySync GPS, SkyPortal WiFi adapter, and StarSense AutoAlign. It runs off DC power with the supplied power cord, but an AC adapter is available separately.
Should I buy a Used Celestron Advanced VX 6″ Newtonian?
A used Celestron Advanced VX 6” Newtonian telescope may be worth purchasing, as the money saved by buying used may be sufficient to purchase a better focuser for the telescope’s optical tube as well as other accessories. Be sure that the mount powers up, slews, and tracks correctly, and is not significantly corroded. The optics in the C6N optical tube should be free of corrosion and other damage to the coating; recoating them can cost more than simply buying a new optical tube assembly. Missing accessories or counterweights can be easily and cheaply replaced, as can a missing NexStar+ hand controller. Parts like adjustment/saddle knobs or the counterweight shaft are also available as spare parts from Celestron or in upgraded formats from ADM.
For visual observation, here are some of our top picks.
- The StellaLyra 10″ f/5 Dobsonian boasts a considerably larger primary mirror, providing superior resolution and light gathering capabilities compared to the Advanced VX 6″ Newtonian. It also includes a wide range of accessories and features while maintaining portability. The 8” model is cheaper and includes the same high-quality features/accessories, but about the same physical size.
- The Celestron StarSense Explorer 8″ Dobsonian offers ample aperture and utilizes Celestron StarSense Explorer technology for easier aiming around the night sky atop its sturdy and easy-to-move Dobsonian mount. Various knobs, handles, and cutouts are included to assist in carrying the telescope.
- The Sky-Watcher Virtuoso GTi 150P shares the same optics and performance as the Advanced VX 6″ Newtonian’s C6N optical tube but offers a collapsible tube for increased portability and a GoTo tabletop Dobsonian mount with manual aiming and smartphone/tablet control. The manual Heritage 150P is identical except for the absence of electronics.
- The Sky-Watcher Skymax 127 AZ-GTi consists of a Maksutov-Cassegrain optical tube mounted on the multipurpose AZ-GTi mount and tripod, which includes motorized tracking GoTo abilities. The AZ-GTi also features the ability to be aimed manually by hand and is controlled via your smartphone rather than a clunky hand controller. The Skymax 127 optical tube delivers comparable performance to the Advanced VX 6″ Newtonian for observing planets and bright targets, all while eliminating the need for collimation adjustments, though it is inferior for deep-sky viewing on account of its narrow field and smaller aperture.
- The Celestron StarSense Explorer 10″ Dobsonian provides many of the same features and a similar form factor as the 8″ model but with extra aperture and simplified collimation. This makes for a user-friendly and relatively portable setup with much more power than the Advanced VX 6″ Newtonian, as well as a much simpler learning curve.
- The Celestron NexStar 6SE delivers marginally better planetary performance than the Advanced VX 6″ Newtonian while offering a much more convenient and portable package. Compatibility with a range of aftermarket focal reducers allows for some deep-sky astrophotography capabilities if the C6 XLT optical tube is removed from the NexStar SE mount/tripod and mounted on an equatorial mount.
- The Celestron NexStar Evolution 8 utilizes Celestron’s C8 XLT optical tube, providing superior light-gathering and resolution compared to a 6″ telescope while maintaining a remarkably compact size. The NexStar Evolution mount includes fully motorized GoTo and tracking features, as well as an integrated lithium battery and WiFi adapter for convenient control via your smartphone or tablet.
- The Sky-Watcher Explorer 200PDS NEQ6 Pro is an 8″ Newtonian reflector specifically designed for astrophotography and mounted on the high-quality NEQ6 Pro mount. This combination makes it a fantastic choice for those seeking a ready-to-go imaging setup. The NEQ6 Pro mount surpasses the Advanced VX with its increased payload capacity, more precise tracking/guiding, stepper motor drives, and enhanced mechanical design.
- The Sky-Watcher Skyliner 300P FlexTube GoTo Dobsonian, featuring a 12″ aperture, serves as an excellent midpoint between large 14-16″ Dobsonians and smaller 8-10″ GoTo telescopes, with the FlexTube design keeping it fairly compact when not in use. Its motorized tracking/GoTo are a huge boon at this size, while the Sky-Watcher FreedomFind encoders enable manual aiming.
- The Sky-Watcher Skyliner 250P FlexTube GoTo Dobsonian features a fully motorized GoTo and tracking system, allowing manual telescope aiming even when powered on, thanks to its FreedomFind encoder system. This model is more compact than a solid-tubed 10″ Dobsonian and offers the same performance advantages over the Advanced VX 6″ Newtonian.
- The Celestron NexStar Evolution 6 presents various mechanical enhancements compared to the more affordable NexStar 6SE and includes a built-in WiFi adapter and lithium battery to simply setup and usage.
Aftermarket Accessory Recommendations
For slightly increased magnification and a more immersive view than the C6N’s sole provided 25mm Plossl eyepiece, a 16mm UWA (41x) is an excellent choice, while a 15mm redline/goldline (43x) serves as a decent budget alternative. A 10mm UWA (65x), or a 9mm redline/goldline (72x), is ideal for medium-high magnification, while for higher magnification, a 4mm planetary eyepiece or 4mm UWA (163x) is a good pick. A Cheshire collimation tool is also a valuable item to keep around to ensure precise collimation for the sharpest possible views with the Advanced VX C6N.
The inclusion of a narrowband Ultra High Contrast (UHC)/OIII nebula filter in your assortment of accessories for the C6N is a wise decision, as it can markedly elevate your views of nebulae, for instance, the Orion Nebula, when employed with nearly any telescope, including the Advanced VX C6N. You can also, of course, use this filter with a bigger telescope in the future, so it’s certainly worth picking one up. In addition, it delivers ample contrast improvement to reveal the faint, wispy Veil Nebula supernova remnant and other low surface brightness nebulae with the Advanced VX C6N under sufficiently dark sky conditions.
A polar scope isn’t provided with the Advanced VX as standard for whatever reason, and attempting to achieve rough polar alignment with only the hole in the polar axis can be both imprecise and bothersome, particularly when it results in your telescope veering off track when you’re trying to locate a difficult target. The stock polar scope that Celestron sells can effectively solve this problem. You will also need some kind of DC power supply, like the Celestron PowerTank Lithium.
What can you see?
The Celestron Advanced VX 6″ Newtonian is capable of both photographing and delivering breathtaking views of nebulae and star clusters. Under moderately light-polluted conditions, the scope can easily reveal stunning details in the brighter emission nebulae such as Orion (M42) and the Lagoon (M8). As you might expect, darker skies and the use of a UHC filter enhance your viewing experience on these objects, and allow you to see fainter nebulae like the Veil, North America Nebula, and the larger planetary nebulae such as the Dumbbell (M27) or the Helix Nebula. 6″ aperture of also allows you to see the characteristic blue and green coloration in small planetary nebulae such as the Ring, Cat’s Eye, and Blue Snowball.
The wide field of view provided by the C6N means it excels at observing large open star clusters, thanks to its wide field of view. The Double Cluster in Cassiopeia, the Wild Ducks Cluster (M11) in Scutum, and the Pleiades (M45) in Taurus are just a few examples of the many clusters that will appear vividly in the C6N’s eyepiece. The brightest globular clusters, such as M13, M15, and M22, can be resolved into individual stars with the C6N, although you will need to use higher magnifications (typically 80x or above) to do so.
Galaxies are also within the C6N’s reach, with 6” of aperture providing enough light-gathering ability to see dust lanes in larger, brighter galaxies like M31, M64, and M82. The spiral arms in galaxies like M51 and M101 are not visible in any kind of detail, but their presence is detectable. The Virgo Cluster is another great target, with the C6N able to show you dozens of its member galaxies, with many individual galaxies fitting into the same low-power field of view.
The C6N does a good job on the Moon and planets as well, though you’ll need a good short focal length eyepiece or Barlow lens to get up to optimal magnifications for viewing the planets. You should have no trouble resolving the phases of Mercury and Venus, along with a wealth of detail on the Moon. Mars’ polar ice cap and a few dark markings are visible at high magnifications of 100x or more when the planet is at its closest to Earth, and you can resolve the disks of all four moons of Jupiter fairly easily, along with their shadows during transits. Jupiter shows the Great Red Spot, its prominent equatorial belts, and many other cloud and atmospheric details. You’ll also be able to resolve the Cassini Division in Saturn’s rings and the planet’s own moons and atmospheric details, the disk of Uranus, and Neptune’s moon Triton. Resolving Neptune clearly, as well as seeing the moons of Uranus or fainter Pluto, will require a larger telescope.
The Celestron Advanced VX 6” Newtonian telescope is, of course, not ideal for deep-sky astrophotography due to its 1.25”-only focuser, which limits what cameras you can use with it and inhibits the installation of a coma corrector. However, with a DSLR/mirrorless APS-C sized or similar small sensor, you can get great deep-sky images of smaller targets where coma can be cropped out, provided you don’t push exposures too long, as this can cause blurred/trailed stars thanks to the limitations of the Advanced VX mount.
Planetary astrophotography with the C6N can be accomplished with the use of a 5x Barlow lens and a suitable high-speed planetary video camera. A 6” telescope is a little on the small side for planetary imaging, but you can still get decent results with good collimation and precision focusing. The Moon, Jupiter, Saturn, and Mars will look excellent if you are fortunate enough to have decent seeing conditions. You can also use the scope with a solar filter to show sunspots, as well as resolve the phases of otherwise detail-less Venus and Mercury. Using short exposures or high gain can also allow you to image the tiny moons of Mars or the faint and distant moons of Uranus and Neptune.