Nebula42 I did it, it does but approximately, there is like 10 degrees missing.

The Daylight Saving Time bug in ASIAIR will cause an error of 1 hour in Hour Angle, or 15 degrees.

Try doing a GOTO (not slew) between two targets that are about 1/2 hour east of the Meridian, and about 1/2 hour west of the Meridian. They don't have to be real stars, just coordinates that have different Right Ascensions -- simply use the same declination angles. If the time settings are all kosher, then the mount should automatically execute a meridian flip between those two targets -- i.e., the mount moves from one target to the other target via the pole. If the time in ASIAIR is bogus, then the GOTO between the two pier sides will simply move the OTA directly about 15 degrees from one target to another (if their declinations are similar).

This will narrow down what bug you are facing.

Chen

Nebula42 Just one question : should I put the real time or the UTC time with the daylight savings?

Nobody knows for sure, since ZWO never published the code where they compute Local Sidereal Time from Local Date/Time and Longitude.

ZWO is somewhere conflating Daylight Saving Time into the equations, where Daylight Saving Time has no place to be.

Local Sidereal Time should be determined only from UTC, Julian Date and Local longitude. Somehow, ZWO people haven't taken any beginner Astronomy classes or read any astronomy textbooks, and they try instead to deduce Local Sidereal Time from Local Time (which includes Daylight Saving Time). Utter rubbish.

Celestial navigational only needs the Julian Date, the UTC and how many degrees of longitude your are from UTC.
Julian Date is easy to compute from Unix Time (it tells you how much time has passed from the time the Sun crossed the celestial equator in Spring). The internet or a GPS unit gives you precise UTC (which is different from British Summer Time in that UTC has no Daylight Saving offset), and you can get local longitude from GPS or Google maps. I don't know why ZWO turned such a simple thing into a bug they have not been able to fix for over 5 years now.

Chen

Nebula42
Actually, I'm pretty sure it would be more like:

In summer, IF the place where you live uses DST, then: you need to put the time back 1 hour. So:
Local Time: 23:00
Time to put into ASIAIR: 22:00
DST: Off

In winter, the place where you live will not have DST, then:
Local Time: 23:00
Time to put into ASIAIR: 23:00
DST: Off

I live in Australia. Everywhere but one state - Queensland - observes DST.
So in the summer - during DST - it is like this in Australia:
Queensland: 22:00
Everywhere else in Australia: 23:00

This means that if you are in the "Everywhere else in Australia" zone then you would have set the ASIAIR back one hour.
i.e. Local time: 23:00, ASIAIR Time with DST Off: 22:00
However, if you live in Queensland, then you would have set the ASIAIR time to be the same as your local time:
i.e. Local time: 22:00, ASIAIR Time with DST Off: 22:00

Happy to be corrected if I'm wrong.

For reference: https://bbs.astronomy-imaging-camera.com/d/12251-daylight-saving-time-reminder

Nebula42 What do you think?

Yeah, follow what Corsair said.

You typically do not have to set the time in the hand controller. Simply turn the Daylight Saving Time (DST flag in the mount off, and let the ASIAIR (in the tablet) push ("sync") the time and location to the mount. From monitoring the USB traffic, ASIAIR appears to "sync" by itself right when it connects to a mount (it used to be haphazard, but the recent versions of ASIAIR appear more consistent).

However, there may be mounts that are stubborn and will reset the time back again. For those mounts, you will need to set the handcontroller's local time manually. FWIW, I do not have to do that with the RainbowAstro mount. I don't even use my hand controller when using ASIAIR -- I simply turn DST off.

Much of this "stubborness" comes from the GPS that are in some mounts (i.e., the mount will try to use GPS). If you have GPS in your mount or handcontroller, turn the GPS off, although just turning DST off will often do the trick.

Basically, ASIAIR only understands Winter time. China does not use Daylight Saving -- Korea also does not use Daylight Saving, but the RainbowAstro mount understands it perfectly. So it is no excuse.

So, just undo the "Spring forward, Fall back" like you do on your clocks and always use Winter time as the local time for your mount even in Summer (turning the DST flag off will also adjust the UTC offset).

All this is because of a huge bug in ASIAIR code. The ASIAIR is using Local Time (which therefore involves DST) as part of the computation for the fundamental time for astronomy called Local Sidereal Time (LST).

LST depends on UTC (Universal Coordinated Time, referenced to the Greenwich Meridian) and your local longitude. It does not depend on Local Time -- I don't know which school ZWO went to, to learn the wrong stuff. And after years of being told to use only UTC and longitude (I even emailed their higher ups directly), they persist on using Local Time, all for the sake of the lowest common denominator - moronic customers who do not know what UTC is, and only know the time on their "smart watches."

Chen