I tried both (using Astroberry, PHD2 is already installed in the package).

For some reason, I could never get the internal guider to perform as well as PHD2. Even using the beautiful multi-star feature that PHD2 has been lacking. Until now.
When I say the same results, I am not talking about a couple of tenths of arc-sec, either. More like 25% to 75% higher total RMS error. This with both softwares using the predictive PEC algorithm and even on the same night, same subject, and few minutes after each other - so, seeing can't have changed that much, in such a small time window.

Another thing that PHD2 has and I highly appreciate is the Guiding Assistant, where it monitors a star and the behaviour of the mount and then suggests you the optimal settings for the guiding parameters.

Now they are finally adding to PHD2 the only thing that it was laking: multi-star guiding. People that have tried it already are reporting in a CloudyNights thread better guiding by 50-90% with it enabled vs normal single star guiding.
It's just a matter of waiting until they release it (it's in "DEV" state) and being ported to Raspberry/Astroberry. Can't wait!

There is one basic difference between the two systems. Ekos does fairly brief calibration every time you start it. PHD2 does a very long and comprehensive calibration once the first time you use it and stores the results for future sessions. This means, for example, that for a first-time use, PHD2 will take up to several minutes to calibrate, but then subsequent starts will use the initial calibration. Ekos will do about a 30 second to 1 minute calibration every time guiding is initiated.

One could argue that PHD2 is better, because it starts up quicker after the first calibration. Or one could point out that as the mount warms up or cools down, it is best to recheck calibration more frequently.

I personally like the Ekos internal guider. It is, for my mount, equal to PHD2 and more convenient. There are, however, a lot more bells and switches in PHD2. I think the good news in this discussion is that there is no real horribly wrong choice between the two.

Hi Jon, Pretty sure that Ekos internal guider can reuse calibrations. Also note that PHD2 can be configured for less calibration points, and Ekos for more calibration points (if that's desired). Given that Ekos internal guide log data can be viewed by the LogViewer app (previously just PHD), it's really a tossup. For me, I use PHD2 but only because I don't have a view of Polaris so I rely on drift alignment which Ekos doesn't have. I'll probably switch back to the internal guider since I've noticed that PHD2's predictive periodic error crashes quite often (and I haven't heard that yet about the ekos implementation of the same feature). A drift align in Ekos (or an align that works just on one side of the meridian) would be a wish list item for ekos...

You can have it today! The PHD directions for building it from source work seamlessly right on the Raspberry Pi. github.com/OpenPHDGuiding/phd2

It looks intimidating but it's really not. And I just followed the instructions in cookbook fashion, there was no need for my programming skills.

I wasnt a fan of the internal guider until ive tried the multistar guiding in the last clear night we had around here. Cant believe it wasnt the default option. So good!

Couldve been an extraordinary good balance and seeing but got down to 0.5", my personal best, with 8.5kg equipment in a eq6r, with 240mm guidescope.

Sent from my SM-G950F using Tapatalk

Depending on how you have your system configured there could be another advantage to phd 2. If you are using a raspberry pi connected to your equipment and connected from another computer controlling the session (not with VNC), then running PHD2 on the pi would could be better for a couple of reasons.

- The pi is closer to the equipment, so short cables for guiding rather than sending signals over the network. There might be less delay.
- Since the pi isn’t running kstars it has some extra processing power and ram that it can dedicate to guiding.
- Taking the burden of guiding off the main computer will allow it to focus on the other tasks rather than guiding.
- if you experience a kstars crash or issue on your main computer such as a power loss or network failure or computer shutdown, the pi will keep guiding and INDI will keep capturing the image, so as long as you can start KSTARS back up before the image is supposed to download, it will be ok. (This has saved me a few times)

That being said, if you are running KStars and INDI on the same computer, whether that is on a pi or on a laptop, most of those advantages disappear. Then it’s just a matter of preference, and as has been mentioned in other posts, the internal guider has some features PHD does not have and PHD has some features the internal guider does not.