Hey there
First off, I don't claim this as my discovery. There are a few older posts on CN about this; however, there a lot more posts about the same issues asking questions and seeking clarification.
This thread is intended to try and help other Nexstar mount users who wish to connect to CPWI without the hassle of a USB connection to the hand controller (HC). I also talk about the changes I have made connecting my Nexstar mounts to ASCOM to virtually eliminate connection drop outs.
Background
I stumbled upon this connection technique through a problem solving experiment that I ran on my CPC1100. I was having constant connection drop outs when connecting to CPWI. I was using CPWI as an ASCOM gateway / hub to then connect things like APT & Stellarium, so that I could do plate solving for my EAA.
Solving problems with CPWI connection drop outs - changes to ASCOM set up
The first thing I did was to disconnect the GPS module. This can be done by lifting the grey plastic azimuth motor cover and then disconnecting the GPS wire connection inside, it's actually marked 'GPS'. I had read about that particular fix years ago but had never got around to doing it. I did it when I had the grey cover off when I upgraded all my azimuth bearings, both the single roller bearing and the small ball bearings in the lower race.
I had read that many users reporting that the GPS can cause unnecessary electrical chatter within the system and can interfere with ASCOM connections. All I can tell you is that I did it and it did instantly reduce the drop outs massively. I don't actually use GPS anyway. Even for people who use various observing locations, it doesn't take 30 seconds to look up where you are and input as a Custom Site.
The second thing I did and perhaps the most significant, was to change the way I was connecting to CPWI via my ASCOM Device Hub Manager. When you install ASCOM onto your laptop, you will by default also have installed ASCOM Device Hub Manager (let's call it ADHM). This is an extremely useful and important part of your ASCOM set up that you should have on your desktop and be familiar with its functions.
To place a short cut to it on your desktop:
C:\Program Files (x86)\Common Files\ASCOM\DeviceHub
Then right click 'Device Hub' and create a shortcut.
Normally, this is how you want ADHM set up. Open ADHM, then:
Tools>>Set Up>>Telescope Device Choose>>CPWI>>OK (You can populate 'Properties' later when you are connected to CPWI)
The changes I made to how other software such as APT & Stellarium connect to ASCOM
So up until now, I had ADHM pointing to CPWI, which is fine, but I also had APT, Stellarium, etc pointing to CPWI in their ASCOM connecting defaults - which was not fine. That is what was causing so many of the drop outs. I conclude that because after I made the changes, the problems stopped.
What I did, was change both APT's and Stellarium's ASCOM defaults to Device Hub Telescope and not to CPWI as I had it previously.
Making this change meant I could connect to CPWI and have APT & Stellarium all playing nicely with each for hours!! Heaven.
The changes I made connecting my mount to ASCOM (and therefore CPWI, APT, Stellarium, etc)
So, with the connection drop outs solved I then investigated my mount / ASCOM connection with a view to seeing if improvemnets could be made.
Improvements in this case meaning freeing up the hand controller (HC) from being connected to my laptop via USB Mini to USB A.
Up until this point, the only Nextstar mounts that could connect to CPWI without a HC USB connection were the CGX & CGXL. They have a USB 'B' port on their mounts for a direct connection to the laptop. That is how I connect my CGXLs when imaging.
However, I also have other Nexstar mounts - Evolutions and a CPC - that I wanted to free the HC of its USB to mount connection.
Long story short - if you have a Celestron Focus Motor installed, you can use the USB 'B' port underneath the motor to connect to your laptop. You still have the Focus Motor connected to the mount via the AUX cable in the usual way.
Using that connection, you can now connect to CPWI without any USB cables having to go through the HC, which I love.
Before I wrote this article this morning, I went into my telescope workshop and tested all this to make sure I was giving you accurate information. I tend to have a big mouth. My heart is in the right place, I believe, but my mouth can get in the way of my brain sometimes. Anyway, I tested my Nexstar mounts and all of the was tested and proven to be correct.
Additional surprise discovery
During my testing, I also discoveerd something else I didn't know before.
If you connect the Focus Motor to a laptop using only the USB B cable and not the AUX cable as well, you can still connect to CPWI but you will only have control of your Focus Motor but nothing else. I'm not sure how much benefit that will be to anyone but I do love discovering new things.
Of course, there is always Celestron Focus Motor Utility, which is a stand alone programme to control your focus motor outside of any ASCOM connection. I have used it often and love it. Find it here:
Open https://www.celestro...pport-downloads
then
* RIGHT CLICK on "Celestron Focuser Utility Program"
* Select "Open in new window"
* When new window opens refresh page
* You should see that the Focus Motor Utility exe has downloaded
Sorry for this long post but I wanted to, and felt it was important to, have all this co-related information in one place with the intent that the trials and experiments I have been through may prove of benefit to some other Nextstar mount users down the line.
With best wishes, the clearest of skies & happy astronomy,
Siouxsie
