Example: If pixel scale is 1 arc sec per pixel, then Dec movement would be 15 pixels per second. This parameter (15) is then used to determine the amount of move command that is sent to the mount. Therefore if the error is 1 pixel, the mount would be commanded to move 1/15 sec at 1x guide rate. This also means that the loop gain is 100%, which means that a 1 pixel error is compensated by a 1 pixel move command.

 

Knowing the pixel scale and the calibration result (parameter number obtained after calibration run) allow you to know if the loop gain is 100% or not.

 

If calibration number is wrong, your resultant loop gain might be more than 100%. If the parameter number obtained after a cal. run is only 7.5 rather than 15 in the above example, then for every 1 arc second position error the mount gets a 2 arc second (1/7.5 second) move command. Loop gain is now 200%. So, the net result is overshoot after every error with the axis constantly bobbling back and forth. The smaller the number relative to the correct number, the larger the overshoot.

 

Rolando