I've been trying external guiding with PHD2 and there are a couple of things that could work better.

1. It would be nice if connecting to the external guider would launch PHD2 - right now you have to launch it via VNC - not so terrible since I generally work with it a little in this mode.
2. when you disconnect from PHD2, it remains looping. or I haven't found a way to stop looping remotely . This is only really an issue because when using INDI camera in PHD2, images are sent to the local Ekos and updated in a fits viewer. Can't stop this without going PHD2 via VNC again.

Anyway, a little more control over PHD2 to start and stop things , and why is the camera image displayed in a fits viewer instead fo the image window in the guide module?

So for #1, I don't think there is any way to easily do this from KStars. You would have to execute a command on the remote computer to start up the program. KStars is running most likely on a different computer so it cannot launch PHD2. Your INDIServer is operating on the remote computer, but which driver would launch PHD2? Would it be a child process of one of the drivers? One possibility could be that INDIWebManager could get a button that could launch PHD2, you might ask Jasem about that. For me, I just made PHD2 one of the startup programs on the PI.

For #2, when you say it remains looping, do you mean you were guiding at the time you disconnected? If you stop guiding, the looping would stop too, and if you started looping without guiding then you probably started this looping from PHD2 not Ekos since Ekos currently doesn't have a looping button, so I am not sure I understand this.

In terms of the camera image, I discovered that PHD2 sends back a star image with every guide command it executes so that is currently what is displayed in the guide module. I guess there could be an option to choose whether to display the guide image or whether to display the star image from PHD2. I found that sending back the entire guide image takes a lot more bandwidth and was preventing my system from guiding efficiently, since PHD2's star image is so much smaller and still lets you monitor the star its tracking.

I found that the best solution was to have my guide Camera, which is a ZWO 120, connected directly to PHD2 instead of using INDI for it, so that all of the guiding information is kept on my Raspberry Pi and I am just using the star image from PHD2 to monitor what is going on. Without using a camera connected through INDI, I found that my guiding was about several times more responsive and the error ended up being much smaller. The reason was because it didn't have to transfer the entire image frame over the network. There is an option in KStars to disable the remote images coming in so if you do happen to be using an INDI connected camera you can still get the same results that I have hopefully.

I think we could still improve PHD2 support a little more, but hopefully the changes I made back in December went a long way to fixing the issues.

Thanks @rlancaste for the comprehensive answer! Thats a good idea to make PHD2 a startup program. I'll do that.

For #2: When you guide internally, you can capture, loop, guide and stop. It would be nice to have those same capabilities when running PHD2 remotely. However, the looping was running because a failure to find a star terminated the guiding - looping was left on.

#3, yes I work this way too. But I have to disconnect the guide cam in Ekos before using it with PHD2. It would be nice to use the INDI camera (WITHOUT reduced performance) so connecting and disconnecting was not required - i.e. leave both Ekos and PHD2 connected to it. As it is, its not so terrible because once I've finished with the guide camera for polar alignment, PHD2 can then use it exclusively.

In reference to #2, PHD2 doesn't provide all the options for KStars to use. Here is what PHD2 provides: github.com/OpenPHDGuiding/phd2/wiki/EventMonitoring. Capture and looping are actually a couple of the options that it does provide, but since PHD2 doesn't send back a full image and because it only sends the star image while guiding, unless the camera is connected to INDI, you cannot get the exposure back to put it into the guide module. In the case of my setup, if I were to tell PHD2 to capture or loop from Ekos, I would not be able to see anything happening in KStars since my guide camera is not connected to INDI. Obviously if you have an INDI connected camera, we could display the images in Ekos since they are being sent to all clients. Currently there is an option in KStars called "Receive external guide frames" which either allows an INDI camera to send its guide frames back to Ekos or you can select to not have that happen and select your guide camera so PHD2 gets the images but Ekos does not.

If you have the option that I mentioned above not selected, then you can use the camera in Ekos all you want, and then when you are guiding, you can select your camera so the frames are not all downloaded.

I found the "Receive external guide frames" setting but it was not checked. I tried guiding again and this time there was no guide cam images popping up. Also checked the network traffic and it was very low - in the KB/s region.

I see whats going on here. The images were popping up because I had done a preview from the guide cam with the capture module so there was a connection to the guide camera and it was being refreshed. Normally, at this point, the guide camera would not be selected except in the guide pane, and here receive is disabled. I haven't been able to test this just now because I don't have my imaging camera right now.