NexRemote Telescope Control for CGEM

My review of the Celestron CGEM continues. This article is dedicated to my experience with NexRemote telescope control. This is the first time that I have ever used NexRemote and some things were a bit tricky. But after figuring it out, I thoroughly enjoyed using it! So I hope to provide some helpful hints on getting you started using NexRemote.

The first thing I noticed when I received my CGEM is that Celestron provided an RS-232 cable for connecting NexRemote to the telescope. One end of the cable has a DB9 connector and the other end has a modular phone jack. This was a surprise since most newer computers do not have a DB9 serial port. Thus, I had to buy an adapter cable to use the USB port on my laptop. Unfortunately, not all USB to RS-232 adapter cables work with NexRemote. I had to do some research to determine which one to buy. I selected Celestron’s USB to RS-232 Converter Cable shown below (note: click on photo to open product page):

Celestron USB to RS-232 Converter Cable
Celestron USB to RS-232 Converter Cable

According to Celestron, the cables listed below are supposed to be compatible with NexRemote as well:

Aten Technologies UC232A USB to DB9 Serial Adapter
Belkin USB PDA Adaptor Cable
Digi 301-1003-10 Edgeport 2C 2-Port DB-9 Compact USB Converter
IOGear USB to Serial/PDA Converter Cable GUC232A USB-to-RS232 Serial DB9 Adapter Cable (ICUSB232)

Installing NexRemote

There was a little snag while trying to install the NexRemote program from the CD. The following screen auto-loads when the CD is inserted:

NexRemote Installation Setup

I clicked on “NexRemote Installation” on the menu and started following through with installation. But then I got this error: NexRemote is not allowed to run on WinNTx. Setup aborted!

Nexremote Error- NexRemote is not allowed to run on WinNTx. Setup aborted!

It turns out that there is a compatibility issue with my version of Windows. To fix it, I shut down the NexRemote installation program and went to the NexRemote files on the CD through Window Explorer. There is a file called “NexRemote Install” in the list as shown below. I right clicked on this file.

Nexremote Compatibility

Then I clicked on the “Compatibility” tab and checked the box to run the program in compatibility mode. Windows XP (Service Pack 2) was the default in the drop-down box which was the correct selection. Here is a screenshot of the final settings:

NexRemote Compatibility

After pressing the OK button, I launched the installation  program from the NexRemote Install file that is shown above. The installation was a success! Note that a restart is required after installation.

Launching NexRemote

Now that NexRemote was loaded, I launched the program from the desktop icon. An odd pop-up box came up telling me that I have 30 days remaining in my NexRemote trial period.

Nexremote Trial Period

At first, I wondered if my CD was just a trial version and not the full program! It was like one of those free trials you get to use for a period of time to see if you want to buy the full version. However, it was simply a matter of inserting my license key that was found on the NexRemote disk envelope. After adding the key, I didn’t see this message again.

Virtual NexRemote Controller

The next surprise was when I launched NexRemote. CGEM was not listed in the “mount model” drop-down. This was odd given that NexRemote came with my CGEM.

CGEM not listed in the available mounts.

It turns out that I did not receive the latest version of NexRemote. The version on the CD was 1.6.14. I figured out that the latest version had to be downloaded from the Celestron site.

Latest version of NexRemote (click on the “Support/Files” tab and scroll down to the software section).

Although the download file says that it’s a “30 day trial”, I did not have to insert my CD key again. I just downloaded the file to my desktop then ran the setup program. When I went back into NexRemote, the CGEM was listed! The new version is 1.6.25.

Connecting NexRemote to CGEM

It took some trial and error before I could actually connect the NexRemote to my CGEM. I had the USB connector (of the USB to RS-232 adapter) plugged into my laptop. Then the serial cable that was provided with my CGEM was connected to the USB to RS-232 adapter cable. The modular phone jack on the other end of the serial cable was plugged into the jack in the bottom of the CGEM hand controller.

Nexremote Cabling Setup

Since the cable was coming off of the USB port of my laptop, I was not sure which PC Port or Virtual Port on the NexRemote to select. After experimenting, I found that the following settings allowed me to connect to my CGEM:

  • PC Port- Com4
  • Mount Model- CGEM
  • Firmware- GEM 4.16
  • Virtual Port- None

Screenshot of the NexRemote settings:


Virtual Controller Setup

After connecting to the CGEM, the virtual hand controller on my screen prompted me to do a setup just like the first time I used the actual hand controller. This included my time zone, date, time, etc.

After the initial setup was complete, the NexRemote prompted me to do a star alignment. It was doing everything that the actual hand controller does when turning on the telescope.

Using NexRemote!

From here on out, it was all fun! I was using the NexRemote virtual controller to hop from object to object. I even got to see the planet Uranus for the first time in years. It was just a small blueish dot, but was interesting none-the-less. NexRemote was working perfectly!

Now I can start setting up my remote operation. My observatory has been vacant since I had the LX200 mounted in there. I need to make a few modifications inside the observatory to accommodate my CGEM. The NexRemote software will be key to controlling the CGEM remotely- from inside my garage!

If you have any questions or comments, please post them in the “Leave a Reply” section below. Also, I have added a survey below to find out if this review was helpful to you.


Clear Skies! Ray Shore

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  1. Please feel free to add comments or ask questions here regarding my article: “NexRemote Telescope Control for CGEM”

    Ray Shore

  2. Jeffry Turner


    This was my first time using nexremote also. I did get it to work by selecting all on the version on cd for the scope mount. Will have to download latest version online so I have it updated. One thing I am very disappointed in is the hand control and being required to plug into the hand control when connecting computer. It seems for a few pennies more Celestron could have put a longer cable on the control and also had a female jack on the hand control so the cable could be unplugged like my meade control does. I can see why so many people have had hand control failures at the cable.

    Needless to say besides this major design flaw the scope did control via nexremote very well, although being an lx user it took some time to get comfortable with the interface.

    I have had a chance to run my mount mount through the paces and did get some imaging accomplished. The mount performs very well. I am waiting for another small scope to arrive so I can test autoguiding out.

    I am very please with how portable my setup is, the very quick alignments, and very impressive goto which drops the object in my ccd fov each and every time.


    J. Turner

  3. Hello Jeffry,

    Thanks for pointing out that “all” can be selected if CGEM isn’t available.

    I’m a bit dissapointed that the computer cable has to be plugged into the hand control too. I didn’t need my hand controller plugged in with my LX200 when operating remotely. But as you say, Nexremote does work very well. Sounds like you’re having a good experience with the CGEM overall. Same here.

    Say, are you going to use the Awesome Autoguider Package by Orion? I’m thinking about getting one of these myself. Looks like a great deal for the refractor and guiding camera.

    Thanks for your feedback.

    Ray Shore

  4. Jeff Turner


    I have the Orion star shoot autoguider already. I ordered up the Orion short tube 80 to mount onto my existing meade 80 APO. Will be guiding with this setup and PHD. I will be getting the new 8″ HD OTA soon, which I already have all the hardware to mount my meade to. I like the flexibility of haveing my 80 with the second 80mm as a quick throw in the car and travel setup.

    Yes, so far overall I am very impressed with the new mount, besides the limited hand control cable issue, everything else has been outstanding so far.

    I am using the celestron polar scope with the mount and found that shiningg a small red led light off to the side of the polar scope lights if up perfectly to rotate the polar scope constellation guides for the night sky and NCP alignment. I am thinking of making a small mod and having this red led permanent to this polar scope.

    I jumped through about 12 various objects the last night I was out with only my DSI IIIC imager in the 80mm scope, and every object was almost perfectly centered in my imaging chip on each goto once I fine tuned my aligment.

    One definite must have item which I had a chance to finely try one from a friend, was the Bahtinov Mask, these are the best small item to own if you image, and make focusing a snap! If you image pick one up or make one yourself from online templates, these are the best item ever invented for focusing!

    The weather has been bad this past week, and snow is coming our way up North. Hopefully, the new short tube 80 arrives and I will have it mounted and ready to try my hand at autoguiding in the near future.

    Sorry about all the typos in last post………fingers were not functioning and was going on zero coffee!

    Clear Skies!

    Jeff Turner

  5. Jeff,

    Good post…lot’s of info!

    I think I’m going to order the Orion Starshoot autoguider too. I plan to do astrophotography with my Canon Digital Rebel DSLR and ED80. I’ll mount the Orion Awesome Autoguider package on the ED80.

    Interesting info on the Celestron polar scope. I didn’t realize they had contellation guides on them.

    Very encouraging news that your CGEM is accurate enough to put the object in the center of the imaging chip. This should be the case with my DSLR as well. I have to get an adapter to mount my ED80 on my CGEM before I can start imaging though. I’d like to see some of your results with the DSI IIIC.

    I’ve been looking at those Bahtinov Masks and it sounds like they work real nice for focusing. They are only about $30 for my ED80 so I will probably get one. Eventually, I’ll be back into Astrophotography!

    Ray Shore

  6. Jeff Turner


    Just checked shipping info and the new guide scope arrives this Monday! Not quite sure how the mounting will go I have several ideas to get it mounted to the rings on my Meade 80mm. Will figure it out when it arrives.

    Since I am new to astrophotography I had purchased Adam Blocks 1st DVD on using Photoshop and have been reviewing it this week. A great bit of confusion on post processing was answered with this dvd. Most importantly I now fully understand using levels and curves to stretch the images obtained and how the functions correlate. This has been a great eye opening experience the light bulb has finally clicked!

    Next time out I plan on setting up and trying out Nebulosity v. 2 which I purchased from Craig Stark. Nebulosity is geared towards controlling my DSIIIC and looks very easy to use to image with. I have spent some time last week reviewing the online NEAIC 2008 presentation by Craig on using PHD and Nebulosity with a great deal of the presentation dedicated to autoguiding, common problems experienced, and imaging on the cheap. This was a great presentation very informative, feel like I gained a great deal of knowledge on the topic. This is available at the following link and runs via online video or I believe may be available for download also

    Send me a private email and I can send off a few pics. I am really looking forward to raising the bar with autoguiding. I am hoping to be ready to image with the new setup by Tuesday. Hopefully, the weather breaks later in the week, and I am able to capture some new images with the new setup.

    I also have to add to my list of to-do’s to make a 6ft. extension cable for the hand control on the cgem. I am worried that the short cable is going to stress the joint where it connects inside the hand control. I believe I read somewhere that a straight through cable will work.

    The DSI IIIC has been great to use. My previous setup was the SAC8 which had a very small chip. My experience so far has been very positive with the DSI IIIC, although I think in retrospect that I would have more flexibility by using the DSI III non color with a slide filter or wheel, regardless imaging is much easier with the larger chip.

    When I am setup again I will snap a few photos of the CGEM and gear and post to the CGEM group at yahoo.


    J. Turner

  7. Jeff,

    I’m checking with ADM on the best way to mount the Orion Awesome Autoguider system to my ED80. Plus, I need an adapter to mount the ED80 directly to the CGEM saddle plate.

    I have a copy of Adam Block’s DVD as well. It is VERY informative! I hope to take my image processing to the next level.

    Thanks for the link to the Stark presentation. I have not done any autoguiding so this will be helpful for coming up to speed.

    I just sent you an email. Looking forward to some of your work with the DSI IIIC.

    Thanks again for all the helpful info!

    Ray Shore

  8. Jeff,

    Thanks for the link. I figured the polar scopes would just have a reticule showing the center of the eyepiece. Putting the constellation on there should help make sure you are aligning on Polaris.

    Once you have autoguiding in place, do you think you’ll need to use the drift align procedure or will the All-Star Aligment routine be enough?

    Ray Shore

  9. Ray,

    The reticule actually allows you to align right on to the NCP. I start by leveling my scope, then proceed to the polar scope and rotate the constellation guides to current star positions trying to be as accurate as possible(I shine a red down polar scope to I can see the guides readily). Once I have the orientation with the polar scope I then proceed to adjust mount to be on top of the NCP ocated in the reticule of the polar scope The whole procedure takes about 3 minutes. Once this is achieved I then do the all star align. I did notice that when doing this procedure and having very accurate coordinates on location that when doing aligment routine all of the alignment stars are very close from the beginning of the alignment procedure. I will have a better feel for exposure capabilities when I have a long night out and test out the new autoguiding setup, weather cooperating that is.


    Jeff T

  10. Jeff,

    Looks like I need a polar scope for the CGEM! I’m looking forward to hearing the results of your autoguiding trials.

    Ray Shore

  11. Mike Wolski

    Thanks for the help with the nexremote software for the cgem. I got the same error message when I attempted installation. Now with your help I have it installed. now if i can find the adaptor cable mabey I can use it. also, if celestron has the usb cable can’t they have inclueded it since no one’s computer has serial ports anymore. makes no sense to me

  12. Mike,

    I’m glad I was able to help! I was surprised that they had a serial cable too. I’m not sure why they haven’t gone to USB yet. Ray Shore

  13. USB is more limited in maximum cable length compared to RS-232, that could be the reason. also makes an extension cable for the hand controller cable.

  14. Thank you again for yet more advice, this time on the CGEM-NexRemote-computer incompatibility issue. There really shouldn’t be such problems on a product that costs $1500. Celestron should bring their included software up to date, issuing it on a new CD, and so, not requiring the purchaser/user to have to search frantically for answers. What would we do without the World Wide Web and sites like yours?

  15. I have a C8-SGT Advanced Series, it is my first telescope as of last Chrismas. So far I only got a couple of pictures of the moon, I used an old camera lense and made a eye piece projection adaptor for a Canon EOS T2i that fits over 2″ eye pieces. I can make out the bands arround Jupiter on the camera’s display but so far have not got the exposure right for a good picture.

    I already have a USB to serial adaptor and made up serial to 4 wire telephone connector. Also picked up a 4 wire telephone handset cable that can be streched out to 20′. Must have done it right; the 1st time I ran NexRemote (downloaded trial version) everything works. The main reason I am trying out NexRemote is to see if the scope will track the ISS satellite with Satellitetracker. Is it just me? The only way I can exit NexRemote is do a restart on my laptop.

  16. Evilgenius747

    I recently got the handheld remote too. Does the port at the back bottom of the controller where you insert the modular telephone plug really comes with no cover?

  17. Bill Needgam

    Hi Roy was wondering if this will work on the newer next star 5+ version. I bought mine about 1 1/2yr ago had to replace the hand control, the clip lock broke off.
    I got a extension cable and had no more problems . love the CGEM had it supertuned by DR. Clay Sherrod of the Arkansas sky observatory.
    I thought nex remote was suppose to work with the hand control off the tele with a port cable that I bought. plugs into were the hand control goes. trying to figure this out before I buy the software. any help would be appreciate any help. thanks Bill

  18. It screws nicely into the CGEM mount, but there is no way to align with the mount axis. On mine, the mounting misalignment arc was off center by 1/2 degree. I unscrewed the back of the polar scope to evaluate the adjust screws (which turn out to not be alignment screws because there aren’t any) and discovered the thing is full of grease which promptly got on the lense. Its tough to clean grease off an etched lens so don’t do that. You can’t see the cross-hairs or etching at night, which is when you need to align to Polaris (unless you shine a red flashlight back into your view). You can get Polaris within 1/2 degree (depending on the mount misalignment) if you sight while the sky is still illuminated and Polaris is visible. I have a permanent pier mount, but if you are using a tripod which hasn’t been aligned you can get a rough polar align use the finder scope, and get pretty close if you know the angle to polaris relative to the rotation pole (see etching on the polar scope) and note that Polaris is about 3/4 degree from the pole. Overall I would say this thing is cute to look through when you get it out of the box, but operationally its pretty much useless for the CGEM. Use the Polar alignment software with the NexRemote instead. That works well with two star alignment and an illuminated crosshairs eyepiece like the Celestron CrossAim 12.5 mm Reticle Eyepiece or other brands. When using timed exposure you need polar accuracy to a few arcminutes.

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