While checking something else out with my ASIAIR and my mount simulator, I stumbled on something interesting this evening (cloudy outside as usual). The ASIAIR's Telescope Setting has set itself to start always with the Lunar Tracking rate, and not Sidereal Tracking rate.
I placed some breakpoints in my program and discovered that the ASIAIR really did not initialize my (virtual) mount to any particular rate (which in itself is a bug), so it did not do any harm since my software initializes itself to use sidereal rate when I open the serial USB port.
However, if your mount does not initialize itself to sidereal rate (or if ASIAIR actually initializes it to Lunar rate), you could have a problem.
To do a check, first start tracking (with almost all mounts, tracking automatically starts right after ASIAIR sends it a GOTO command; tracking can also be started from the ASIAIR Telescope Setup page's Tracking switch). And then check your mount's hand controller to see what the tracking rate is set to at that point.
For mounts that support multiple (solar, lunar, sidereal, King) tracking rates, once ASIAIR starts tracking, the different tracking rates also show up right below the Tracking switch selector.
If you find that the mount is not tracking at Sidereal rate, use the hand controller and force it to sidereal rate. For good measure, also change the tracking rate in ASIAIR's Telescope Setup window to the sidereal rate.
By the way, the difference between Lunar Rate and Sidereal rate is about 0.356 arc second of RA movement in 1 second of time. If you are using a 3 second guide exposure, that corresponds to a movement of more than 1 arc second. This will not only cause a guide star to form an oblong star on the guide camera, changing the true centroid, but it also imposes a constant bias (think of it as a force) of 1 arc second per guide frame that the guide pulses have to fight against.
If you have no access to the hand controller, you can try toggling the tracking rate (change to Solar rate, and then change back to Sidereal rate) in the ASIAIR interface to manually set the mount to sidereal rate.
Chen
