astrosatch Is it possible to measure dec backlash with asiair somehow?
If you mean your mount's declination backlash, check the PHD2 Guide Log that is saved to your storage (inside ASIAIR/log folder).
If you want to measure declination backlash well, first rotate your guide camera angle so that the red and blue lines in Calibration Data are aligned with the x and y axes (the gray axis lines).
You can set guide camera angle quite accurately by plate solving the guide scope. The plate solve solution shows the camera angle -- if you set the camera angle to 0º, 90º, 180º or 270º, the following steps should give you a pretty good idea of your declination backlash.
Then do a Guide calibration. The Data that are shown are in the following columns
Direction,Step,dx,dy,x,y,Dist
For declination measurement, look at the North-South movements. The "direction" should start with North steps. The step number will go from 0 to N (N is determined solely by the Calibration step size (in milliseconds) in Guide Settings. Try to calibrate so that it finishes the North steps in 10 to 20 steps.
The dx and dy units are in pixels.
If you have set the Guide camera angle so that red and blue vectors in Calibration Data are aligned with the x and y axes of the camera, either the dx or dy column will be small. The dx or dy column that changes more is your declination axis (in pixels).
Watch the numbers go from 0 pixel north to past 25 pixels north. ASIAIR will then start a southwards movement. When it finishes the south movements, a perfect mount should return dx (or dy) back to zero. If it is not zero, that is the amount of backlash (in pixels).
The plate scale of your guide scope then determines how many arc seconds the backlash in pixels corresponds to.
If you want to see where the backlash is primarily occurring, just manually plot the dx (or dy) values. Depending on how your gears are meshing, it may not be a sudden backlash recovery, but a slow recovery until the gears have fully meshed and you are in the linear dx (or dy) change again.
You can use the phdlogview program to see other problems of your gears during calibration. ASIAIR does not show the details in its Calibration Details.
Chen