darkmatter The graph shoots off the scale, RA RMS keeps increasing and the only way to get it back is to do a new calibration.
Next time, perhaps you can look at the rate it that it shooting off: how many arc seconds of RA (on the graph) per second.
If it is shooting off at a rate of about 1x sidereal rate (16 arc seconds in RA per second of time), then it might be because tracking got turned off.
If it is shooting off at other rates, then it could mean that the pier side is somehow changed and autoguiding has the wrong sign (-RA instead of +RA, or vice versa)-- the problem did not happen to appear within 1 hour of the object transiting the Median, did it?
Also worth noting is whether an eastern star always shoots off in the same direction, and if a star west of the Meridian always shoot off in the opposite direction (or the same direction). All that could help in guessing what could be wrong.
It is not just the Avalon, but pretty much no other mounts has a special setting for guiding. You simply send a slew rate of between 0.25x to 1.0x sidereal to the mount, and you then pulse guide by literally slewing it for N milliseconds, where N is determined from how much PHD2 wants to correct, multiplied by the scale that is obtained during autoguiding calibration. So, if the slew rate is somehow changed after a dither then something is bad -- the slew rate really should not change, since dither should be also done at the current guiding rate, so no one should be changing the rate.
Do you know where I can get a copy of the StarGO Communication Protocol? If so, I can try to add it to my mount simulator and see what ASIAIR is trying to send to it.
The StarGO protocol might be based somewhat on the LX200 protocol, since the StarGO Legacy protocol is very close to the LX200 protocol. But I have not come across any document that describes it and since I don't own an Avalon, I never bothered to write them to ask.
By the way, did you try switching to using the StarGO Legacy protocol (in StarGO and in ASIAIR) to see if that works?
If anything like what you are seeing happens to me, I would have abandoned ASIAIR for INDIGO Sky a long time ago. The only thing still missing in INDIGO Sky (which also runs on a Raspberry Pi) is a simple Polar Alignment routine; but Polar Alignment does not work for you on ASIAIR anyway.
The stars around your Crescent does show about a one pixel drift in RA tracking, but you are right, the focus is pretty good. The elongated pixel could be caused by a wind gust, too.
It is interesting that you have a Linear. I nearly bought a M-Zero when I was upgrading from my EM-11 mount's load capacity, but in the end went with the RainbowAstro RST-135 instead. But I still crave that single fork design :-). Avalon knows good design and elegance.
Chen
