I’m wondering what the best setting for the autofocus is and what type of equations I need to calculate the best minimum diameter for the stars because I’m running into a problem where my focus isn’t good. After autofocus, I need to adjust some steps to get the perfect steps, and I believe some backlash may happen, yet getting the right setting may solve some problems also.
One more thing is it normal that the yellow rings around the stars be way too big comparing it to stars size?
Lately though, I have been using this somewhat simplified set of steps here (you’ll still need a basic understanding of AutoFocus in SGPro for some of the terms to make sense and the link above can help make sense of that):
I would recommend sticking with 9 data points (for now). This is a good value for dialing AutoFocus. In terms of the step size:
Step 1: Enable Image History and then start a Frame and Focus loop using your desired exposure length for AutoFocus. This will display, on each frame, the current HFR. The objective here is, using manual focus adjustments, minimize the HFR. This focus doesn’t need to be perfect.
Step 2: Note the current position of the focus controller and note the HFR at this point
Step 3: Once you have approximate focus, making sure to move the focuser in the SAME direction as the last movement you used to achieve this manual focus (eliminate backlash as a variable), move the focuser slowly until HFR is about 3 time larger than the “in focus” HFR above. It doesn’t matter if you rack out or in, just that you move in the same direction as the last focus movement in Step 1.Once here note the focus controller’s reported position.
Step 4: Find the delta (absolute value) of the starting focuser position and the focuser position that yielded 3x HFR. This value is approximately half of the distance a focus run should move. With that in mind, go ahead and double this value and then divide by 8. This should be your starting step size (not necessarily your final one though).
Step 5: Setup AutoFocus with the new values and run it. As long as you start AutoFocus from a position of focus, you should observe a “U” and, notably, the tips of said “U” should be approximately 3x of your in focus HFR. If they are not, this points to a different problem (focus movement issues… backlash, binding, slipping, etc).