Multiple VCurves -which ones to say yes and which ones to say no or delete for best Autofocus results in calculating a RoboFire V curve. I have studied the manual and the Wiki. The Wiki says that autofocus can be improved by making more than one VCurve. Looking at my table of VCurves what comprises a good VCurve that should be checked “yes” vs. no” to use in the calculation. I know what the data is showing but not what it means as far as how to interpret which is the better curve(s) for the best autofocus result. For example do I want the lowest or highest PID? Do I want the left and right steps HFD to be as close to mirror images of each other? Or do I choose the curves with the smallest step increments?
My related question is once the actual visual curve is no longer shown on the screen is there a way to have it display again from the table of individual Vcurve data?
Leonardo has been very helpful and responsive answering my new user specific support questions but I thought this was a good general forum question coming from someone new to VCurves and truly automated focusing.
Thanks so much,
Bob
Dear Bob,
we have talk about in this forum but happy to answer.
Vcurve if your focuser work fine and without backlash or slippage and your resolution is on human capability its all equal so nothing to do, just 3/4 vcurve are enough. I see this on 90% of user running VCurve.
To decide the vcurve when things are different you cannot only based on the number in the table but you mus see the vcurve graph during the realization and see how V shape is your vcurve and decide after to remove. If have an horizontal series of points (backlash or cable retains or slippage) , if one side have a total different slope pendence, if seeing ruin the running with outliers points: this is a curve to remove.
Looking at table you can only decide to remove the vcurve having a slope left/right value really different from the average. In a real world this will be not possible (ideal vcurve = equal slope value with different sign). Different value of slope right/left from average means a bad vcurve, if the resolution is so high this diffrence can be amplified in this case more vcurve are need to have a good average.
Before delete always use the yes/no mechanism, in this case you can reinclude the vcurve if needed. Press the recalculate button and apply.
PID is something in second order to evaluate, depends on your focuser resolution the difference so better to not evaluate. Also because it is a direct result of slope difference.
What means slope difference : uncollimated instruments, tilt of sensor / focuser tube, particular correction system like Petzval can amplify this difference
In all of this there is the AI engine fixing things for you during the real autofocus.
I hope this helps.
All the best
Leonardo
Thanks Leonardo. Very helpful information verifying what I had assumed. I did notice that the graph being realized for my latest VCurve, after having made a few settings adjustments, showed the points on the curve progressing in a nice straight 45 degree line on both sides with no horizontal outliers. So if it looks pretty and uniform then basically it is good. 
All the best,
Bob
I will try to comment on this old topic.
I have much more difficulty to get a good set of Vcurve using SCTs (C11 and C14) than with my refractors.
Regarding the SCTs data set I have put the data table of Voyager in a spreadsheet and calculated the offset from my near focus HFD in number of focuser steps, for left and right slopes and PID of each recorded Vcurve.
I see that initial result seems to me bad, as the spread of the calculated move to focus from near focus HFD exceeds the scope CFZ.
I then looked at the calculated results to remove the Vcurves giving most distant focus point versus average. I had to remove (using No) more than 50% of initial dataset ending with only 5-6 Vcurves to get a spread of focus point well inside the CFZ.
I don’t know though if this selection method is valid.
Leonardo, would you comment on that?
Clear skies
Antoine
Hi Antoine,
SCT are not a good telescopes for astrophotography , they are affected by so many problems. If you want to use be sure to not oversampling too much and using it on a night with a really nice seeing and overall when acclimatated (usually a couple of hour).
If you need to put data in a spreadsheet !!! you are doing something wrong, I suggest to use support email and ask support.