Few nights with Celestron CGX – night I

It is pretty close to summer solstice, so plenty of time for preparing setup for night session. Day is extremely long, and night ends in no time. But for Celestron CGX mount (that I received from Delta Optical for tests and review)  you don’t need much time for preparing, although the process differs a little, when compared for example to EQ6-R mount. Night of June, 19th I decided to spend on some visual observations and lucky imaging. Soon after dusk I assembled CGX mount. It took me about 10 minutes of work. Mount head is attached to the tripod with three screws and required allen wrench is placed under the mount head handle. The same allen wrench is used to tighten and loosen four azimuth locking screws. It is worth to notice, that CGX has no polar scope as standard equipment. This is available as separate purchase, and it is mounted in remote arm. There is no place for polar scope in RA axis due to internal cabling. There is an advantage of this solution – all mount head sockets are placed at fixed mount part, so they do not move when mount is working. This way we can avoid some twisted and turned cable problems.  Azimuth adjustment range is not large, so it is recommended to set up tripod accurate to north, because if you miss it for more than three degrees you will need to move it legs later. 

Celestron CGX mount with SCT 11" tube attached
Celestron CGX mount with SCT 11″ tube attached

When first stars popped up I turned on power. Here are the steps I followed to align CGX mount – the whole process took me less than 10 minutes:

  • set up home position – it is done automatically, because CGX has built in home position indexes. For this reason the head should be levelled before we star alignment (there is bubble level indicator)
  • enter location coordinates. CGX has built in real time clock, so you do not need to enter date and time
  • select first alignment star and centre it. I used 16mm eyepiece attached to Celestron C11 scope (175x magnification)
  • select second alignment star and centre it.
  • add one calibration star – Ras Algethi. Centre it.
  • select Polar alignment function. Hand controller displayed polar alignment error for 10’ in altitude and 2 degrees in azimuth.
  • start polar alignment. Mount rotates to calculated position and you need to centre star using only azimuth and altitude knobs 

That’s it. Then I collimated C11 tube and did a quick goto to Jupiter. Planet has landed about 10 minutes from the 16mm eyepiece field of view centre. Although Jupiter was pretty low in the sky (altitude below 30 degrees) view was pretty spectacular – belts, divisions and few curly details were obvious. I quickly replaced eyepiece with QHY163C color camera and made a picture – probably last time in this season.

Celestron CGX mount back - supply and hand control cables attached
Celestron CGX mount back – supply and hand control cables attached
Jupiter on June, 19th imaged with SCT 11" on Celestron CGX mount. Planet was pretty low, below 30 degrees.
Jupiter on June, 19th imaged with SCT 11″ on Celestron CGX mount. Planet was pretty low, below 30 degrees.

Then I moved scope to epsilon Lyrae double pair. Both components were split and one of them landed almost in the field of view centre. There was still not dark (about 10pm), so I left the setup and went home for some time. I came back around midnight to catch a little of dark sky. Epsilon Lyrae was still near the centre in the eyepiece. Conditions were not bad (at least for my suburban location) – seeing was good and transparency as well – I estimated NELM little bit better than 5mag, Milky Way in Cygnus was hardly visible. I pointed telescope to some well known objects – M57, M56, M27, some small globular clusters. Targets always landed no further than 1/2 of 25mm eyepiece field of view (112x magnification). At the end I reached for harder target – Minkowski 1-64 planetary nebula in Lyra. Hard target, but successful with averted vision. After few last nights with astro imaging sessions and 24h Le Mans race I was little bit tired, so at the end I put back QHY163C camera to focuser and did M57 lucky imaging. It is totally 200 frames 3 seconds each unguided – lucky imaging. Pixel scale was 0.29”/px.

M57 Ring nebula in Lyra. Lucky imaging with QHY163C camera and SCT 11" on Celestron CGX mount. 300 x 3 seconds frames, unguided
M57 Ring nebula in Lyra. Lucky imaging with QHY163C camera and SCT 11″ on Celestron CGX mount. 300 x 3 seconds frames, unguided

At this first test night Celestron CGX mount passed the exam. Setting up is quick, alignment is accurate and polar alignment pretty convenient (despite lack of polar scope). DC motors and gears do not racket too loud, and goto is pretty fast. There was no problem with finding targets with 16mm and 25mm eyepieces (magnifications 175x and 112x). C11 tube wobbles a little when pushed with hand – mainly in RA axis. I suspect it is due to spring loaded worm gear mesh. This gear can be adjusted by customer, but I did not want to do it now. Anyway it is not disturbing even in moderate high power magnifications (up to 300x) and does not happen when you push your eye against eyepiece. You need to use more power. 

C11 on Celestron CGX - nice tandem. Astroshed with astroimaging setup in the background.
C11 on Celestron CGX – nice tandem. Astroshed with astroimaging setup in the background.

3 thoughts on “Few nights with Celestron CGX – night I”

  1. HI there,
    Thanks for your review. How well does this mount track with and without autoguiding ? Thanks for your prompt and kind reply.
    Henri-Julien Chartrand
    Mont Royal QC Canada

    1. Hello Henri-Julien,

      Unfortunately I had no opportunity to check it – the weather broke and I needed to return the mount to the shop. But in this price range I may recommend iOptron CEM60 (version without encoders). It is well tested by amateurs, periodic error is in the range 3-5″, and guided tracking RMS is at the level of 0.5″ (both axes cumulative). It is pretty much enough even for sites with good seeing. Both worm wheels are large diameter (146mm) so the accuracy is quite good (assuming the Chinese manufacturers quality is similar, larger wheel provides better precision).

      Clear skies!

  2. Hello Lucas,

    I was able to get a sweet deal on a brand new CGX. I totally agree with your conclusions so far. As for tracking, it is excellent, meaning I can nail the object dead center in a 12mm eyepiece with a 900mm refractor well over 5 minutes. PEC is between 5-6”.
    With guiding, I can bring my total error down to 0.21. As you know, some conditions apply. Happy with that. I tried imaging M51 last weekend from my backyard. Out of 120 subframes, only 4 showed some elongated stars. I don’t know about your final evaluation of the CGX but I am happy with my decision. True, the CEM 60 is not only lighter but a better value and performer overall. Pricing got me on the Celestron.
    Your posts represent still excellent references for me. Keep them coming.
    Henri-Julien Chartrand
    Montreal, Quebec, Canada

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