PHD Log exhibits steps in the star SNR curve on the 1 degree dome moves

from firmware.

Proposal

• The existing @GAR "Goto azimuth degrees" command remains unchanged for backward compatibility.
• Introduce a new firmware command, @GSR,sssss "Goto step position". This allows the rotator to be moved to an exact whole step position. The firmware protocol was not designed to include floating point numbers so the proposal is to accept a step position and not an azimuth. The target whole step position must be computed by the driver or application plug-in.
• There are 55,080 whole steps per revolution, so this gives a theoretical positioning resolution of 360/55080 = 0.00654 degrees.
• Driver or application can compute the step position for a given azimuth as circumference / 360 * target azimuth
• Driver or application can obtain circumference using the @RRR command, which returns the circumference in whole steps.
• Dead zone still applies. Moves smaller than the dead zone will be ignored. Dead zone is settable using the @DWR command.

This will then require a new version of the ASCOM driver that uses the new command. Optionally, other drivers and plugins would also have to be updated.

Feasibility

Initial investigation suggests that this could be added to the firmware reasonably quickly and with low risk. The firmware would remain backward compatible with all existing drivers and plugins.

Recommendation

I recommend that this feature should be added to the firmware and a subsequent version of the ASCOM driver.

@nexdome Are you happy for me to go ahead and add this feature?

from firmware.

The experimental firmware version seems to work perfectly - I checked backwards compatibility with ASCOM driver 3.0.1 and ran it through its paces across the 0 point as well (left and right of zero azimuth)

from firmware.

from firmware.