As I research and learn more about guiding, the equipment used for guiding compared to the equipment used for imaging seems to be awful important. I recall several anecdotes about how your guiding setup should scale to your imaging setup, with many arbitrary ratios and “golden rules” thrown about.
My current imaging setup is a Nikon D5300 in a Skywatcher 300P. The pixel scale for this is 0.54 arcsecond/pixel. The guiding setup is a 60mm refractor, at 240mm focal length, with a Touptek guide camera. The pixel scale for this comes to 3.22 arcsecond/pixel. This gives a guiding to imaging ratio of 5.96. I’ve read that several people have successfully used a scale similar to this for years.
In an ideal world, if we wanted guiding accuracy of one pixel in the image, we would need to catch and correct a movement in the guide camera of the same size as the size of a pixel in the imager. This would be require detecting a movement of at least 0.54 arcseconds.
\frac{3.22 \textrm{arcsecond}}{1 \textrm{pixel}} = \frac{0.54 \textrm{arcsecond}}{x \textrm{pixel}}\implies x \approx 0.17 \textrm{pixel}
This is the “MinMo,” or “minimum movement,” setting in PHD2.
