Technical Specs
The Celestron CGX, while being a new, innovative design in the world of astrophotography mounts, still shares some features with its EQ6 style predecessors, and as such, there are still some basic technical specs that you should know.
- The Payload Capacity
The CGX has a weight capacity of 55 lbs, or 25 kilograms, which I found to be far improved over the Sky-Watcher EQ6-R or Celestron CGEM, being 5 and 7 kg more, respectively. This means I’m able to load the CGX with far more weight while still getting good guiding.
However, this payload number can sometimes be difficult to interpret for starters. That’s because Celestron, along with most other mount manufacturers, is unfortunately not very specific as to how much weight on the mount is acceptable for specific purposes and how it affects the tracking and guiding accuracy of the mount.
- It is commonly accepted amongst astronomers that if we are doing visual observing or planetary astrophotography, we can load up the mount to the weight limit or even exceed it by a few kgs, as small-scale errors are not very noticeable visually.
- In contrast, when we’re taking images, the mount’s tracking accuracy has to be far more precise because the images we take will show streaking easily. Adding more weight to the mount can increase the magnitude of tracking errors and ruin any images we would take. As such, I recommend using no more than ½ and ⅔ of the supposed weight capacity for astrophotography.
It is important to keep in mind that this is a very broad statement, and tracking/guiding accuracy depends on many factors that are too numerous to list here.
- Dovetail Saddle Style and Counterweights
The mount accepts both Vixen V (narrow style) and CGE or Losmandy D (wide style) dovetail plates, which allows me to use any telescope that has a standard mounting system with the CGX, provided I can balance the mount with enough counterweights while keeping the weight on the mount under around 55 lbs.
The CGX uses a standard ¾” diameter counterweight bar and thus accepts any of the weights designed to fit this size, such as the two included 17-lb counterweights as well as smaller 11-lb and 7-lb units designed for other mounts.
- Nexstar+ Hand Controller
The CGX also includes a Nexstar+ hand controller, which is also used across all of Celestron’s computerized mounts. It includes over 40,000 objects with Messier, NGC, IC, and custom coordinates for finding any target in the sky that I choose.
- The Portability
The CGX weighs 44 lbs, not including the tripod, which is also somewhat heavy at 19.2 lbs. This can be somewhat of a problem for some to carry the mount, but this is necessary for the mount to withstand strong wind gusts and vibrations while keeping images sharp.
For me, once I got a good grip on the mount, it wasn’t too hard to move. The built-in carry handle also helped.
Mechanical Features That I Loved
The CGX is packed full of new features and overall improvements. Celestron listened to its user base and remedied many of the issues and concerns found with their mounts, like the CGEM II and AVX.
- Addition of Belt-driven Worm Drives
For starters, the CGX comes with belt-driven and spring-loaded worm drives, an incredible upgrade over the CGEM that greatly improves guiding accuracy. Mounts like the Sky-Watcher EQ6 and CGEM use gears to connect the motor to the worm drive (the most important gear in any mount), which can create problems where too much space is between the gears, causing an issue called backlash.
Backlash can be seen during guiding. It effectively makes some guide pulses ineffective, as any corrective action is stuck in the gap between gear teeth.
A belt drive cuts out the middle gear and instead connects the motor to the worm gear with a toothed belt, which eliminates all backlash. The worm gear is also spring-loaded, which ensures it is well-tensioned. This also reduces backlash and makes adjusting the spacing manually not necessary. Luckily, the CGX comes with belts preinstalled, whereas in mounts like the EQ6 and AVX, belts were something I had to manually install, and worse, in the CGEM, I had no option to install the belts at all.
- Homing System
The CGX features a homing system. This is a system where the mount can locate its “home” position without any external input, which is where the mount rests when not pointing at anything.
Homing moves both mount axes (Right Ascension and Declination) automatically to their home positions without any sort of outside input. This is especially helpful for observatory systems where the mount is always polar aligned but you may not have access to the mount. With homing, you would be able to be sure of the mount’s positioning without something like plate solving or star alignment.
Homing is a rarely seen feature in mounts at this price point and is a premium feature found in the CGX, sure to make the lives of astrophotographers easier.
- Improved Polar Alignment
The CGX features a completely new, redesigned polar alignment base plate. In the case of the CGEM II mount, when I tried to adjust its azimuth polar alignment, the mount stuck and skipped, making it impossible for me to align the mount closely to the celestial pole. With the new and improved polar alignment plate in the CGX, the amount of friction between the mount head and tripod has been greatly reduced.
I also like that it features improved adjustment knobs, which make alignment far easier than with the awkward, circular knobs found on the CGEM.
The mount is also able to go all the way down to 3 degrees latitude and a maximum of 65 degrees, which allows me to use the mount in locations very close to the equator and very far from it.
Software Compatibility
The CGX, of course, is Celestron’s best astrophotography mount yet. There are some features listed above that make this an excellent mount on the inside, but I need to point out that CGX also includes some great features that make the mount a joy to use in the field.
As with any other Celestron mount, the CGX works with the StarSense AutoAlign, SkySync GPS, and SkyPortal WiFi adapter accessories. If you don’t want to use WiFi or a PC to control it, you can use the provided NexStar+ controller instead.
The CGX has full computer control and support, based on the new Celestron PWI software/interface. The PWI software allows me to completely bypass the hand controller, which was an unnecessary step when we’re doing deep space astrophotography.
With PWI, the time-consuming step of entering the time and date into the hand controller is not necessary either. This is thanks to the CGX’s included USB Type B port, which allows you to connect directly to the mount without a hand controller or adapters—just get the suitable cable, and you are good to go.
Celestron PWI is a fully functional planetarium software that is built around CGX support. With this software, I can see where the mount is pointing in real time. It also allows me to update the mount’s positioning model without having to do any star alignment via plate solving.
Luckily, the PWI is also ASCOM compatible (ASCOM is an open-source program that allows devices to communicate with software), which means the mount is controllable with any standard image capture programs, for example, SGP, NINA, APT, and other similar programs, which you can use to plate solve (align your mount via images of stars), slew to various targets, and perform meridian flips automatically.
Using the CGX for Visual Astronomy & Planetary Imaging
The CGX mount is sure to make visual observation a joy.
I could use a very large 14” SCT or similar Cassegrain or a 12” Newtonian atop the CGX for visual and planetary imaging purposes; these are some of the largest non-Dobsonian scopes available on the consumer market.
The mount uses the Nexstar+ hand controller, which is, in my opinion, superior to the Skywatcher alternative as it is easier to use, which becomes an important factor late at night.
The Nexstar+ hand controller also includes over 40,000 objects in its database and an internal time clock, which means that I do not have to enter the time and date every time I start up the mount if I choose to enable it. The controller includes nine slew rates for intricate and accurate slewing and pointing, which means I can go from rate 9, which moves the mount several degrees per second, to rate 1, moving at half the speed of the stars. The Nexstar+ also includes a red backlight, which lights up the text on the hand controller without ruining my night vision.
The pointing accuracy of the mount after a 3-star alignment is also excellent.
The CGX includes a built-in polar alignment feature/routine, which was incredibly useful to me for visual observation. It calculates your alignment error based on your three-star alignment, which is incredibly useful for observers who do not want to use the polar scope or those who have no clear view of the celestial pole.
The CGX can take a very high amount of weight for visual use, but that also means that the mount itself is fairly heavy. This becomes a major issue that you will have to think about if you want a mount with such a high payload capacity as the CGX.
Using the CGX for Deep-Sky Astrophotography
Thanks to many new features and improvements, the CGX is an excellent performer in the field regarding guiding accuracy, which is sure to make your images look excellent without streaking. Thanks to the easy computer connectivity, I can slew around with ease without ever even having to use the hand controller.
Users of the CGX can expect sub-arcsecond guiding with appropriate payloads and guiding setups. I could easily use an 8-9.25” SCT/reducer, 11” RASA, 6” refractor, or 10” Newtonian on the CGX for long-exposure imaging. A 10-11” SCT also works if I don’t push exposure times too long.
Should I buy a Used Celestron CGX?
The CGX is a fairly new product, so you might have trouble finding a used one that’s in working order. However, if you can do so, there’s no reason not to buy a used CGX.
Replacing missing counterweights or the hand controller is fairly trivial.
Alternative Recommendations
The CGX is one of my top picks for an equatorial mount. However, here are a few other mounts that you may want to consider:
- The Sky-Watcher AZ-EQ6i is smaller and has slightly less capacity than the CGX but features stepper/belt drives along with a retractable counterweight shaft, the ability to be used in alt-azimuth mode with two telescopes, and Sky-Watcher’s FreedomFind technology to allow for manual aiming.
- The Sky-Watcher EQ6Ri Pro is similar to the AZ-EQ6i but lacks a USB-B port, FreedomFind technology, or an alt-azimuth configuration.
- The Losmandy G11 Gemini II has similar weight capacity to the CGX, though it’s not nearly as technologically well-equipped.
