These options are distinct.
Guide->Options->Guide -> Settle:
In the KStars code, this option is known as ditherSettle.
I can tell you this option is used by both the Internal Guider and by PHD2 Guider. I haven't looked too much into how the internal guider uses it, but PHD2 is sent this parameter BOTH any time it is told to guide AND anytime it is told to dither. The parameter is not optional, so we have to send it even if it is 0. So when using PHD2, KStars doesn't use this for option itself, but tells PHD2 to do it. I know this because I worked on the code that allows Ekos to communicate with PHD2. Here is the documentation which explains how PHD2 uses the parameter.
github.com/OpenPHDGuiding/phd2/wiki/EventMonitoring. Now, it is possible that it gets ignored under certain conditions or its also possible that maybe it doesn't always use the full time, or it is possible it was changed in a different version. I don't know, since all I know is what they say in their documentation. PHD2 is a little cryptic about it, but they say "minimum time to be in-range before considering guiding to be stable" and I believe it should be how long they wait until PHD2 reports "SettleDone." We programmed Ekos to wait for the "SettleDone" event before confirming that the dithering is completed or the guiding is started.
KStars->Settings->EKOS->Capture -> Settle:
In the KStars code, this option is known as guideSettle.
I can also tell you about this option. This is an option that is used by the Capture module and is independent of your guiding method. This is implemented entirely in KStars and is not sent to PHD2 to handle. Basically KStars starts a timer after the dither success is reported, and KStars waits this long before it begins taking the next exposure. It is a very simple option.
My thoughts:
It is my belief that what should happen is that the dither command is sent, then the mount moves, then the it waits the ditherSettle time, then the guider starts trying to guide, then it waits the guideSettle time, then the next capture is started. So if both of these options work as advertised, then I think both are necessary.
- The ditherSettle time is needed because you wouldn't really want your guider to try to start guiding until the mount is done its motion.
- The guideSettle time is needed because you wouldn't really want your image to start capturing until the guider has settled down and is guiding well.