Hi folks,
If your hand controller has a Daylight Saving Time (DST) setting, turn it off. You should then enter UTC offset and local time as if it is winter.
Turn off DST and if your city observed DST, set the Date and Time of the mount by subtracting an hour off current observed UTC offset and add an hour to the local time.
Long answer:
I just looked at what the ASIAIR is sending to my mount simulator. My longitude is about -122º (I am in the Pacific Time zone), and my current time zone offset is -7 hours, with Daylight Saving active.
The local time is about 10 AM and the Local Sidereal Time (LST) is 23.
When I ran my simulator and connected the ASIAIR to it, the ASIAIR firmware sends 9 AM and a UTC offset of -8 to my virtual mount.
Notice that local time 10 AM with UTC Offset of -7 Hrs and DST on will convert to the same UTC as local time of 9 AM with UTC offset -8 and DST off.
The time ASIAIR sends to the mount will generate the correct UTC if you also turn any DST flag off. If the DST flag on your mount/hand-controller is on, then the time that ASIAIR sends will be an hour off.
UTC is normally used to compute the Local Sidereal Time (LST) from the local Longitude. Those three numbers are related, and they don't change with the seasons. It is very important to get LST correct -- that means UTC and Longitude needs to be correct.
The Right Ascension (RA) of an object is related to the LST by: RA = LST - HA, where HA is the hour angle of your mount. If the mount is physically pointed at the Meridian, its hour angle is precisely zero.
The LST is how the mount determines the RA of the object in the sky, from the HA on the ground. The HA is the mechanical angle of the polar axis and does not change if the mount is not moving or tracking.
If Local Time, UTC Offset and Daylight Saving is wrong, then UTC is wrong. If UTC is wrong, or Longitude is wrong, then LST is wrong. If LST is wrong, then RA is wrong. If RA is wrong, nothing works properly -- GOTO will move to the wrong coordinates, Meridian flips will occur at the wrong time, etc.
As long as the UTC is correct, all should be good.
However, if you have turned on DST on your mount or hand controller, then the local time that ASIAIR pushes to your mount will be converted to the wrong UTC if the mount thinks it is operating in Daylight Saving Time.
In one of the past versions, all you need to do is not click on the "Sync To Mount" button. That way, the mount keeps its own preset time. Sometime in the last couple of releases (there has been so many beta releases, I no longer remember when), ASIAIR always pushes the local time and UTC offset (but without DST) to the mount upon initial connection.
So, again, turn off DST on your mount, let the ASIAIR send the wrong time to the mount with the non-DST UTC-offset. The UTC should then be correct.
If your hand controller also reads out UTC, you can check to confirm.
My primary mount (RainbowAstro RST-135) also has an LST display. If your hand controller has LST display, you can check that too with the LST time that you can get from web applications, or with the SkySafari's advanced data and time window. Remember that penultimately, everything depends on the Local Sidereal Time, and not on Local Time, and not even on UTC.
At least you can test it all out in the day time.
For what its worth, my RainbowAstro (Korean) mount also does not understand DST. China and South Korea do not use DST, so unless their engineers are western trained, they may not be sensitive to the problems from seasonal time changes.
Clear skies,
Chen