Help with controlling a Telescope via Macbook.


I’m trying to connect the Plugable pl2303-db9 adapter to control a telescope (Synscan and EQ5 mount).

I’ve downloaded the latest drivers but cannot connect via Stellarium or Skychart. I’ve been through all their help files but nothing appears to recognise the cable.

I’m using:

Macbook pro (usb2)
OSX Yosemite
RS232 cable supplied with Synscan controller
EQ5 mount

The drivers seem to be installed ok under USB.

I don’t understand the pinout diagrams and can’t find any more info, so I’m stuck! Any help, gratefully received! !](](


Hello Jurgen,

I am sorry to hear this. We either have a long and strenuous path ahead of us because of legacy software issues, or this is going to be a quick and easy fix.

I will take the path of “least-resistance-advice” for now and start with the easy fix.

In your terminal, take a look at the output of the following command -> ls -l /dev/tty.*

If you installed the appropriate Prolific kernel module, one of the instances should be labeled as “/dev/tty.usbserial” in your output. Instead of ttyUSB0 try using usbserial (/dev/.tty.usbserial). I hope this information helps.

Kind regards,
Plugable Technologies


Thank you Patric.
I get the correct result in Terminal as described: /dev/tty.usbserial

I’ve tried this in Stellarium and Skychart(CdC), but I’m afraid the software doesn’t connect to the telescope.

Best wishes,


Hi Jurgen,

I profusely apologize for the delayed response. Can you please try /dev/cu.usbserial?

Under connection settings, do you have more options than only localhost? Does it list COM ports? Is there anywhere in the menu where you can set a COM port?

It is really hard for me to reproduce since we do not have a telescope to test this with.

Kind regards,
Plugable Technologies


Hello Jurgen,

Just wanted to ask if you are up and running or still need any assistance on this matter?

Kind regards,
Plugable Technologies


Hi Patric,

Thank you! Yes it all works fine now. Thank you very much for all your help :slight_smile:


Hi Jurgen,

You are welcome. I am happy to hear, you are up and running again. For more timely responses please contact us anytime at

Kind regards,