Optical Tube
The Advanced VX 700 Maksutov uses Celestron’s “700” Maksutov-Cassegrain telescope, a 180mm (7”) Maksutov-Cassegrain telescope with a focal ratio of f/15 and a 2700mm focal length. It is identical optically and mechanically to the Sky-Watcher Skymax 180 and the former Orion 180mm Maksutov-Cassegrain. The “folded” optical configuration of the Cassegrain design uses a convex secondary mirror and a hole in the primary mirror to achieve a very long focal length in a compact package, with the 700 Maksutov having a physical length of just 22″, despite the focal length being equivalent to over 100”.
Maksutov-Cassegrains use a spherical meniscus front corrector lens, which looks like a salad bowl or contact lens, to correct the aberrations of their spherical primary mirror and secondary mirror. The corrector is made of crown glass, just like what is used in the lenses of many eyepieces and refractors.
The Maksutov corrector lens is machined out of a larger block of glass and precision-polished to a spherical curvature, rather than being subject to the complex cutting, bending, and grinding processes that go into making a Schmidt corrector. The spherical curve of a Maksutov corrector is also easier to test for quality than the complicated shape of a Schmidt corrector. In most Maksutovs, the secondary mirror is just a reflective spot on the surface of the corrector lens, sharing its curvature. This means that one less optical surface needs to be made, and mechanical misalignment is less likely to happen. As such, Maksutov-Cassegrains are easier to manufacture to a high standard of quality than Schmidt-Cassegrains and seldom require collimation, though knocking one out of alignment is still possible, and the back of the Celestron 700 has push-pull hex screws to adjust collimation if it is truly necessary. You would collimate it just like a Schmidt-Cassegrain by pointing at a defocused star, but by adjusting the primary instead of the secondary mirror.
Maksutov-Cassegrain telescopes actually require a slightly larger primary mirror than the corrector plate itself due to how the corrector plate spreads the light out. Older 180mm Maksutovs made by Meade or imported from Russia have 8” diameter primary mirrors to solve the problem, which is the reason 180mm became a standard to begin with. The Celestron 700 Maksutov and other versions, such as those sold by Orion and Sky-Watcher, do not. As a result, the actual aperture of the Celestron 700 is estimated to be between 170 mm and 175 mm, depending on the position of the primary mirror and the focal plane of the eyepiece or camera being used.
Like many other catadioptric telescopes, focusing the Celestron 700 Maksutov is conducted by adjusting a knob at the back to move the primary mirror backward and forward to adjust the spacing between the two mirrors, which has a huge effect on the placement of the focal plane thanks to the “magnifying” nature of the secondary mirror. This also stops an eyepiece or camera from moving physically, which helps keep it balanced on a mount. Any moving-mirror telescope can suffer from “image shift” when focusing, causing the view to appear to rock back and forth or wobble. This can be easily confused with mechanical vibrations until you notice that your target doesn’t return to the field of view when you let go of the telescope. Image shift can be a big problem for a telescope with a long focal length, especially when taking pictures, but the Celestron 700 Maksutov doesn’t have this problem very often.
The Celestron 700 Maksutov has a proprietary threaded port on the back, which the included 2” visual back screws onto. Similarly to the C6 and C8 Schmidt-Cassegrains, the Celestron 700 Maksutov and most other Maksutovs offered by Celestron and Sky-Watcher cannot fully illuminate a 2-inch field. It would have to have a larger central obstruction to do so, which would impair performance and contrast. The interior baffle is 33mm wide at the back, so you can get a maximum field of view of a little over ¾ of a degree before vignetting starts to kick in. This is negligibly wider than the field stops of the widest-angle 1.25” eyepieces, so most 2” eyepieces are basically useless in this telescope. The provided 2”, 28mm eyepiece does not have a field of view larger than that of a 32mm, 1.25” Plossl, so you won’t see any vignetting with it, but pop in a big SWA or UWA ocular and you’ll notice.
To attach to the Advanced VX mount, the 700 Maksutov has a CGE-style dovetail plate running the full length of the tube. The CGE plate is similar to a Losmandy-style plate and will fit any mount saddle capable of carrying either design.
Accessories
The Advanced VX 700 Maksutov telescope includes a 2-inch screw-on visual back and a 2-inch mirror diagonal. As was already said, most 2″ eyepieces can’t be used with this instrument because they vignette too much. You get one eyepiece, a 28mm L.E.T. ocular (essentially a Kellner) with a comfortable twist-up rubber eyecup. This eyepiece has a magnification of 73x and an apparent field of view of about 60 degrees. With the 700 Maksutov, the true field of view is about 0.8 degrees. This eyepiece is suitable for low-power viewing, but additional eyepieces with shorter focal lengths are going to be necessary to use this scope for high-magnification observations of the Moon, planets, and double stars.
The Advanced VX 700 Maksutov also includes a 9×50 finderscope, which would be overkill for a GoTo telescope were it not for the extremely long 2700mm focal length of this instrument, which can make attempting to aim with a 6×30 or red-dot sight irritating. The magnification and crosshairs of the finder provide additional accuracy, which helps speed up alignment.
The Advanced VX Equatorial Mount
The Celestron Advanced VX mount is a fairly cost-effective equatorial GoTo mount, making it an ideal match for the 700 Maksutov. The heavier CGEM and CGX mounts really serve no purpose with the 700 Maksutov, as it is fundamentally not meant for deep-sky imaging, no matter how good a mount you use. The Advanced VX can comfortably hold the 700 Maksutov with plenty of capacity to spare, requiring two 11 lb counterweights which are provided with the telescope. The dovetail saddle on the Advanced VX can hold both Vixen-style plates and the 700 Maksutov’s CGE-style plate, but Losmandy-style plates won’t fit without an aftermarket saddle – keep this in mind if you’re considering using the 700 Maksutov in conjunction with another telescope that shares the Advanced VX mount.
While marketed and designed for deep-sky astrophotography, the Advanced VX is not the best option for imaging, mainly due to some poor mechanical design choices and software complications. The Sky-Watcher HEQ5 is better for this application, but it would not be able to hold the 700 Maksutov due to its smaller tripod and lower weight capacity. However, for the purposes of visual use and planetary imaging with the 700 Maksutov, the Advanced VX is pretty much flawless, and it will work well enough for imaging if you don’t push its limitations too much. Our full review of the Advanced VX goes into more detail on some of its drawbacks for deep-sky astrophotography.
To set up the Advanced VX, you’ll need to assemble the mount, install the counterweights, and then slide on the 700 Maksutov optical tube assembly. Don’t put the telescope on until the weights are secured to the mount. Once these are in place, you balance the telescope on the right ascension axis with the counterweights and balance it in declination by sliding the tube back and forth in the dovetail saddle. After your first time doing this, you can mark the dovetail and counterweight bars to know exactly where to place the counterweights and telescope tube for proper balance in the future.
Once the telescope and Advanced VX mount are completely put together, balanced, and level, you’ll need to do a polar alignment before you turn on the mount and use the hand controller to do a star alignment. Celestron does not include a polar scope with the Advanced VX by default, which appears to be a cost-cutting measure, but with a heavy, long focal length instrument like the 700 Maksutov, polar alignment is critical for frustration-free viewing or astrophotography. Without a polar scope, you can try alignment with Celestron’s All-Star Polar Align, but it takes longer and isn’t as accurate as just sighting through a polar scope.
After a simple 2- or 3-star alignment process, the NexStar+ hand controller that comes with the Advanced VX mount can automatically point and track over 40,000 objects in its database. The mount can also be controlled by WiFi using the SkyPortal WiFi adapter or by connecting the NexStar+ controller to a PC using a MicroUSB cable. The Advanced VX’s GoTo and tracking accuracy are generally fine with the 700 Maksutov, assuming you did a good job leveling, balancing, and polar aligning it. But at a focal length of 2700mm, even small errors caused by bad alignment, balance, or mount problems will show up over the course of a night. To compensate for this problem, the Advanced VX allows users to sync the mount on new alignment stars throughout the night.
Should I buy a Used Celestron Advanced VX 700 Maksutov?
Since the 700 Maksutov just came out, it’s unlikely that you’ll find a used one in bad shape. However, as always, make sure that the mirror coatings are clean and bright and the front corrector lens is free of fungus. If the “spot” on the secondary mirror is broken, it is hard to fix and re-coat, and it can’t be replaced because it is a part of the corrector. Cracks in the corrector will completely rule out any chance of it being usable. The Advanced VX mount should be able to power up, slew, and track flawlessly, though if it is missing a tripod or hand controller, these parts are fairly easy to replace, as are the star diagonal, finder scope, or eyepiece. A missing visual back is rather annoying to replace, but a new one can be found online.
Alternative Recommendations
The Advanced VX 700 Maksutov is a very specialized instrument, and most good telescopes of equal or larger aperture can usually provide on-par performance for small targets while winning on deep-sky objects with larger fields of view and greater light-gathering ability.
Under $1200
- The Apertura AD10/Zhumell Z10/Orion SkyLine 10 offers considerably more capabilities than the Advanced VX 700 Maksutov, such as more light gathering and resolution along with a wider field of view. It’s easy to set up and transport, and includes a plethora of provided accessories.
- The Explore Scientific 10” Hybrid Dobsonian offers a lot of capability in a compact, quickly assembled package with high-quality optics and a sturdy Dobsonian mount. The 10” Truss Tube also offered by Explore Scientific is even more compact and adds features like cooling fans and a dual-speed focuser knob.
- The Celestron NexStar 6SE is a bit less powerful than the 700 Maksutov but cools down considerably quicker and offers a wider achievable field of view, as well as weighing less and being a lot more compact for storage and transport.
- The Sky-Watcher Virtuoso GTi 150P is only slightly less capable than the Advanced VX 700 Maksutov but thanks to its collapsible tube and tabletop Dobsonian mount it is hardly bigger than the 700 Maksutov optical tube when collapsed. The GTi 150P features full motorized GoTo and tracking operated via your smartphone, and can be aimed manually as well.
$1200-$1800
- The Apertura AD12/Zhumell Z12/Orion SkyLine 12 easily bests the 700 Maksutov in all areas, though it’s somewhat bulky even when disassembled. As with the AD10/Z10, you get a variety of high-quality features and accessories.
- The Sky-Watcher 12″ FlexTube Collapsible Dobsonian is more portable than a standard solid-tube Dobsonian of its size but doesn’t include as many features or accessories as the AD12/Z12. A GoTo version is also available which adds motorized slewing and tracking but can still be aimed manually if you wish.
- The Sky-Watcher 10” FlexTube GoTo Dobsonian has a collapsible tube to slightly increase portability as well as fully motorized GoTo and tracking capabilities, while still allowing manual aiming too.
- The Celestron NexStar Evolution 6 is similar to the NexStar 6SE, but includes a battery and Wi-Fi adapter built in for added convenience. It also uses higher-quality gearing in the mount head.
$1800+
- The Explore Scientific 12″ Truss Tube Dobsonian is extremely portable owing to its collapsible truss tube and features a high-quality, all-metal build along with a dual-speed 2” Crayford focuser and built-in cooling fans.
- The Celestron NexStar Evolution 8 is similar in planetary viewing capabilities or slightly inferior to the Advanced VX 700 Maksutov but is considerably more portable and offers more options for deep-sky viewing and astrophotography.
- The Celestron Advanced VX 9.25” SCT is similar in its delivery of high-quality planetary views to the 700 Maksutov but is superior for deep-sky objects owing to its larger aperture and shorter focal length. It also boasts much faster cooldown time on account of the thin Schmidt corrector plate.
Aftermarket Accessory Recommendations
The included 2”, 28mm LET eyepiece provided with the Advanced VX 700 Maksutov is just fine for low-power, wide-field viewing. For higher power, an f/15 telescope can handle even the lowest-quality eyepieces, such as goldlines, redlines, and cheap SWAs, but this telescope is expensive enough that premium oculars are worth the additional cost. We would recommend something in the 18-22mm range, another ocular between 12-16mm, and your highest power ocular be between 8-10mm. Even the best 7” telescope cannot handle above 350x magnification, even under the best atmospheric conditions one could ask for. The Explore Scientific 82-degree range are great eyepieces, and the set of their 18mm (150x), 14mm (193x), and 8.5mm (318x) units would be ideal for the Celestron 700 Maksutov, as would the much cheaper option of the 20mm, 15mm, and 9mm goldline/redline oculars.
While a Maksutov-Cassegrain is primarily a planetary telescope, a UHC nebula filter never hurts to add for enhancing views of nebulae under any sky conditions at low power. The Orion UltraBlock is a great pick; a 2” unit can screw onto the provided star diagonal for use with either 1.25” or 2” eyepieces.
A dew shield for the Advanced VX 700 will prevent condensation from forming on the front corrector, which fogs up the images and can damage the glass and its optical coatings. The dew shield also helps reduce glare and improve contrast while providing a physical barrier to avoid accidentally touching the corrector. A heated dew shield is unnecessary due to the thickness of the Maksutov corrector, which makes it cool down a lot slower than a Schmidt corrector plate. Conversely, however, the telescope takes so long to cool down to ambient temperatures that wrapping the whole tube in reflective insulation and/or installing a cooler that inserts into the telescope is almost required to achieve sharp views.
While you’re not going to be doing any deep-sky imaging with this telescope, inaccurate polar alignment with the Advanced VX will be irritating when attempting to do high-power planetary viewing or imaging as well as GoTos across large stretches of sky. As such, a polar scope or PoleMaster is needed. You’ll also need either an AC power cord or a rechargeable battery of some sort to run the mount, such as the Celestron PowerTank Lithium or a similar generic battery which can be attached to the tripod legs of the Advanced VX if you wish.
What can you see with AVX 700 Maksutov?
The extremely long focal length of the Advanced VX 700 Maksutov limits deep-sky viewing. Most open clusters do not fit in the field of view, though smaller ones, such as M11 or M35, still look great. The brightest globular star clusters, such as M13, M3 and M15, are able to be resolved into individual, sharp stars. Thousands of double stars can be split and should display perfect concentric Airy disks under good seeing conditions with the 700 Maksutov.
During moments of good seeing, planetary nebulae such as the Cat’s Eye or the Ghost of Jupiter delight, displaying their turquoise or blueish colors and revealing fine detail with the 700 Maksutov. You can also split double stars right up to the theoretical limit of a 7” telescope with the 700 Maksutov, and nebulae such as Orion and the Lagoon delight—particularly with a UHC filter—though the view of them can feel a bit claustrophobic. Galaxies will require dark skies, but you can see dust lanes and hints of spiral arms in some of them, as well as galaxy groups and clusters.
The 700 Maksutov is, of course, a planetary, lunar, and double-star telescope, and that’s where it does best. The phases of Mercury and Venus are easy to see, and the Moon shows limitless detail, with tiny surface features such as Rimae Alpes or craterlets in Clavius visible during moments of good seeing. Mars shows a number of dark markings and its polar ice cap when it is at its closest to Earth, and by blocking out its glare at high power, you can even see its tiny moons Phobos and Deimos if you’re lucky. At high power on a good night, Vesta appears slightly out of round when it is close enough to Earth. Jupiter shows myriad colorful cloud bands, storms, and the Great Red Spot too. Jupiter’s four large moons, the Galilean moons, are resolved as clear disks, with perfect jet-black shadows during transits; you can visibly tell Io’s poles appear a darker shade and might even be able to resolve Galileo Regio, a brownish spot on Ganymede, on a very good night.
The 700 Maksutov can of course show you Saturn’s rings, as well as the Cassini division in them; it’s a little small to be able to resolve the Encke gap, but it can be observed too on an exceptional night. Saturn’s brown and tan cloud belts appear along with its blue-gray poles. Saturn’s moon Titan appears as a tiny gold dot, with the other half-dozen visible moons of Saturn observable as star-like points.
Uranus’ green-blue disk is resolved clearly at high magnification, but its moons are just beyond the light-gathering power of the 700 Maksutov. Neptune will require good seeing to clearly resolve it as a tiny azure ball and not a dancing fuzzy “star”, but the 700 Maksutov should be able to reveal its moon Triton next to it even on a mediocre night. Pluto was once bright enough to observe with the 700 Maksutov but is too dim to see without a larger telescope for the foreseeable future as it retreats from the Sun and grows dimmer with each passing year.
Astrophotography Capabilities
The long focal length, incompatibility with a focal reducer, weight of the Advanced VX mount, and limited illumination of the cameras mean that the Advanced VX 700 is essentially incapable of deep-sky imaging.
Planetary astrophotography with the 700 Maksutov can be done with a 2x Barlow lens, a high-speed, high-resolution planetary video camera connected to a laptop, and the appropriate capture software. A more powerful Barlow than 2x will bring the telescope above f/30, which is simply too powerful; even f/30 can be a bit much, and you may want to look for a specialty 1.5x or 1.8x unit. If the telescope has been properly cooled down, the 700 Maksutov will delight with high-quality photos of the moon and planets taken under good seeing conditions.
