Corsair So, for mounts such as mine - HEQ5 Pro, where an EQMod cable is used to connect the mount from a USB 2.0 port on the ASIAIR Plus to the HC Port on the mount, the ASIAIR Plus is now the "Hand Controller" for the mount and that is controlled by the device you use to run the ASIAIR App.
Actually very close to the truth.
The details are this:
You can typically separate a mount into two sections. One section is just the mount's two motors (one for RA axis and one for declination axis). These motors only know their angles relative to the mount itself. For example, instead of RA, the motors only knows its own Hour Angle (the angle the mount makes relative to the Meridian), and the declination angle is a fixed amount, independent of the pier side -- i.e., it does not understand how to meridian flip.
The other section of a modern mount (which does not exist back in the 1960s) is a computer that converts RA and Declination angles in the sky to the HA and declination motor angles. This section of the mount makes it a "GOTO mount." For example, the relationship between RA and HA is:
HA = Local Sidereal Time (LST) minus RA.
The RA of a target is a fixed coordinate. LST changes as time passes, so the HA also changes as time passes, As a result, when tracking the target, the mount moves the amount LST changes, or 15 degrees per hour.
If LST is wrong (as in the ASIAIR during Daylight Saving Time) then you will not be pointing at the correct part of the sky.
OK, on to EQMOD. What EQMOD is is some code (a library) in your computer (e.g., ASIAIR) that replaces the second section above. I.e., EQMOD computes HA from RA, etc, and send the motor angles directly to the mount, instead of sending RA. All the time offsets etc are now inside the computer (ASIAIR) and are now consistent. Meridian flips are now also performed by EQMOD instead of by the mount's microprocessor.
BTW, except when using EQMOD, ASIAIR does not know how to perform Meridian Flips. All it does is to issue a GOTO command to the mount when the OTA is on the wrong side of the pier, and the mount executes the Meridian flip. With EQMOD, ASIAIR sends the EQMOD library a GOTO command, and if the OTA is on the wrong pier side, EQMOD then creates a path through the pole to drive the two motors to perform the meridian flip dance.
I have not seen where ZWO has acknowledge using EQMOD code or what they did to it to incorporate into ASIAIR. EQMOD requires the GNU LGPLv2 license, and any modified code has to be be publicly published. If not, it is in violation of intellectual property laws.
Chen
