I have stellarmate OS on a raspi 4 connected over wifi to w a windows laptop where i run kstars/ekos. The raspi has an explore scientific mount and a qhyccd guide camera.

I have been assuming that i should start phd2 on the pi rather than on windows and in preference to the internal guider -is this correct?

You have options, but probably best to run the internal guider (using multistar). You could run PHD2, but if you did this, you'd want to run it on the Pi4. With the latest updates to the internal guider, there's no real benefit to using PHD2 unless you can't see polaris (so need drift align from PHD2). The internal guider implements multistar guiding, Periodic Error prediction, and logs in a format compatible with the PHD LogViewer. So, probably best to just use the internal guider. The major difference you'll notice right away is that the calibrations are shorter in Ekos (but these are configurable if you so choose). You also won't have a "guiding assistant", but most folks don't really need that. Cheers, Doug

Ok. thanks.

You can guide equally well with either. And PHD2 could run just as well on your Windows client via INDI. EKOS guiding is probably simpler to set up in the EKOS environment. The main difference is that you CAN run PHD2 on your Pi4 if you want to. The main reason for doing that would be to minimise any latency in transferring the guide images over the network. If that is a problem for you then you have the option.