As I mentioned above, the imaging scale of the combo main scope-main camera is 1.61 arcsec/pixel and the imaging scale of the combo guiding scope-guiding camera is 2.39 arcsec/pixel. This means that a 1 pixel movement on the guiding camera is equivalent to 1.48 pixels in the main camera.
Now if I want to have a total dithering of 13 pixels on the main camera, the guiding camera would have to move 8.77 pixel (13 / 1.48).
In this case and just to be clear, I should choose “medium” dithering in SGP while keeping 8.77 in PHD2 to get the desired movement in the main camera (13 pixels), correct?
Just to chime in a little here with a related tip. For settling, since you are using PHD2, I recommend figuring out what your guide RMS is in guider pixels, and set your settling in SGP to no less than that.
I’ve found in my own testing, as well as when assisting others with settling issues in SGP, that if you try to settle below your guide RMS, if and when it happens, it is mostly by chance. This can greatly increase the amount of time it takes to settle, without any clear benefit.
If you settle at your guide RMS in guider pixels, then you can settle pretty quickly (couple/few seconds usually, vs. say 30, 60, 90 seconds.) So if you have a guide RMS of say 0.55", in guider pixels with a scale of 1.61", that would be 0.89 pixels. You would want the settle factor in SGP to be say 0.9. On the other hand, if you had a guide RMS of 0.8", then you would want the settle factor to be 1.3 in SGP.