oneredpanther
Yes, i understand a great PA is a prerequisite. I always start by leveling the tripod first, and when i put the mount head on it i check the level again and adjust if necessary.
Next, when doing PA, i get it as close as i can, and then tighten the Az bolts and the Alt knob, and then i hit Refresh to plate solve again. Tightening the Az bolts and Alt knob usually throws off the PA again, so i redo the process until it's very precise. I can usually get it under 00° 00' 30" total error without much trouble. Under 10" would be nice, but will need a lot more work i think. Will definitely put more effort next time.
Now, after some more reading through these forums, i understand that my calibration step was way off (8000). Apparently i first need to determine the pixel scale (arc-seconds per pixel) for my guide scope, using a tool like this:
https://astronomy.tools/calculators/field_of_view/
I have a 174mm mini and a WO 50mm guide scope, so the resolution turns out to be 6.04"x6.04" per pixel.
I want to scope to move about 2 pixels per calibration pulse. The plate scale will convert that to arc-seconds per calibration pulse. So if the plate scale is 6" per pixel, and i want 2 pixels, then i want to move 12 arc-seconds per pulse. I use 0.5x sidereal rate as the guide rate, so this 12 arc-seconds corresponds to 12/(15*0.5) = 1.6 seconds. So, the Calibration Pulse should be set to 1600 milliseconds. If i find that it takes more than 12 steps to complete 25 pixels, i should just increase the Calibration step, and vice versa. Done.
Next, the Ra and Dec Max Duration: i understand this needs to be left at default values, so either 2000 or can be set to 2500. It simply limits how much PHD2 is permitted to apply per guide frame. If i set it too low to match my mount, it will not be able to keep up with the mount errors.
Aggression: i see that the default value was 70% for Ra, and 100% for Dec. This part i need to read more about because i don't really understand if i should leave it at default, or start from 0% for both axes and move up and experiment.
Guide camera exposure: since this is a harmonic mount, the general recommendation seems to be to give it 1s exposures, some even recommend 0.5s. But again some conflicting info there, supposedly it can be 3-5s as well.
Assuming i have average seeing, no wind, in a Bortle 4 location, with 10" PA total error, would this be a good starting point to start dialing in the guiding?
I just want to learn how to control and troubleshoot this stuff on my own, and help the folks in my astronomy group do the same.
Cheers!
