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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Meridian Flip Configuration

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Indeed, thats wrong. The meridian flip is issued as soon as the constraints are met. If a capture is running, the mount waits until the running capture is finished an pauses it until the flip is completed.

So for testing with the real hardware, there is no need to wait for good weather, Simply position the scope close east of the meridian and have it tracking. Then a meridian flip should take place.
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4 years 1 month ago #49366

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Mea culpa then - has this changed? ISTR that I had run into this, though about a year ago.....
4 years 1 month ago #49367

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I would say we introduced it roughly a year ago. Meanwhile the meridian flip is completely independent from Capture and Scheduler
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4 years 1 month ago #49368

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Despite your comment that the meridian flip is independent of the capture module, my simulation didn't perform the flip unless the capture module was running. This seems consistent with my experience under the stars.
4 years 1 month ago #49369

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Hm, that's strange. Could you please post the logs? Maybe there is something else wrong - or just a new bug occurred.
4 years 1 month ago #49372

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Replied by Brian on topic Meridian Flip Configuration

Just tried this inside and it seems to perform the flip without any capture taking place. Using Kstars 3.40 01-06-20
4 years 1 month ago #49375

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I ran another simulation without capture, and the mount did the meridian flip on schedule. I must have erred on my previous simulation.
4 years 1 month ago #49419

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OK, good to hear. There are still some seldom situations where at least the simulator does not do the full roundtrip, but I think we have eliminated most of them.

And what about your real hardware? Did you do any dry runs?

- Wolfgang
4 years 1 month ago #49423

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I haven't been able to make any dry runs with the mount. Hopefully, I'll be able to get some during daylight tomorrow (and image tomorrow night?).
4 years 1 month ago #49441

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Out with the mount only just now. The target is at +0h 2' + and the mount is on the west side pointing east. However, if the scope were on the mount, it would have already hit the pier. Any suggestions on how to define the mount motion so this doesn't happen? All my issues to date have been with the scope hitting the west side of the pier.
4 years 1 month ago #49472

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That's two minutes - 0.5 degree past the meridian? Had you just done a slew to this position? It could be in the zone where the mount may think it hasn't passed the meridian.

If you can't track two minutes past the meridian then you will have problems with long exposure imaging. Imagine if you are taking 5 minute images. An image starts one minute before you reach the meridian but it won't finish until 4 minutes past and that's the first time that a check can be done to see if a flip is needed.

What i think is needed are hour angle limits. They are:
A tracking hour ange limit. This is the hour angle beyond which the mount must not track. When it reaches this limit tracking is stopped and the acquisition process is paused. Normally this would be well past the meridian, 30 minutes or so, but it could be less, even in some cases before the meridian is reached.
A flip hour angle limit. This is the hour angle which is the earliest that a slew command will do a flip. Normally this is a few minutes after the meridian but some mounts - the Celestron ones for example - can be set to do the flip up to 20 degrees before the meridian.

The flip process should also be managed using the Pier Side property when this is available. At present this isn't used, it uses hour angle. As a result there's a lot of scope for confusion where a mount does a flip earlier than expected and the flip process does another one or, worse, the flip process does one too early. The system now thinks that a flip has happened but it hasn't and it tracks into a hard stop.

Given these things the acquisition process could be made more flexible and reliable. With reliable pier side (NOT simulated, that just moves the problem into the driver) the flip process can be managed correctly and witth hour angle limits things such as mounts with restricted movement can be handled.

I'd have liked to have sorted this out but the complexities and lack of documentation in the Ekos sources make it impractical for a newcomer. I've tried and the majority of my time is spent fighting my way through multiple layers of undocumented code trying to deduce what it's doing. That's not my idea of fun.
4 years 1 month ago #49480

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Good news, folks, we are starting to work on it. It will make the meridian flip more robust - hopefully - but the code complexity will grow again. Since there are mounts that now their pier side, others not, some can be forced into a meridian flip, others not etc.

- Wolfgang
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4 years 1 month ago #49497

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