Re: GTO CP3 connection problem via COM port in Windows 10

Ray Gralak

Hi Henry,

Before connecting the driver open Windows Device Manager and find the COM port(s) that are present on your system. Then open the AP V2 Driver ASCOM Setup. The driver does not automatically discover which port the mount is using so you must select the proper COM port. Select each port and click "Check Port" until you locate the port. Then close the window. The driver should now connect

Also, do not run Voyager or any other ASCOM client as administrator. It should not be required to run any ASCOM client applications as administrator as that may cause a second instance of the driver to start if you also have another application connected.

If you still have problems with take notice of the COM port the driver is trying to connect with to make sure it matches the COM port the mount is connected to. If you are using a USB/serial converter sometimes they try to allocate a new COM port every time they run or after booting. If you have one that does that then try updating its device driver. If that doesn't help try a different USB/serial converter, or if you have a desktop get a serial port add in card.

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:

-----Original Message-----
From: [] On Behalf Of Henry Kwok
Sent: Saturday, March 14, 2020 12:51 PM
Subject: [ap-gto] GTO CP3 connection problem via COM port in Windows 10

Hi Ray (or anyone else who can help):

Since I have upgraded to Windows 10 (from Windows 7) I have a problem connecting to the mount via COM port
using ASCOM.
Basically the first attempt at connecting to the mount after a fresh boot up of the machine will always fail.
However, if I try again the second time it will work.

For example, I normally start APJog, then click connect. It will launch the mount ASCOM driver window, but it will
fail to detect the mount.
To solve the problem I will have to click connect again (which does nothing), then click disconnect (so to close the
mount driver window), then click connect again and then everything will work fine from there.

I have also tried to connect to the mount from Voyager - and I see the same problem (i.e. first attempt at connecting
to the mount after a fresh boot will fail).

This is a fatal issue, but more a nuisance.

I have noticed this problem since upgrading to Windows 10. Windows device manager does not report any error.

BTW, Voyager always run in administrator mode. I have set APJog to run as administrator as well, because if I
don't and try to run Voyager after APJog the mount will not connect.

Is there some setting I am missing?


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