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

Bi-monthly release with minor bug fixes and improvements

What is the right way to control meridian flips?

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If the mount tracking can be disabled that would be ideal.

I wonder if it would be best to handle these details in the driver's though as a set of limits that fall within the mount's capability. These would be exclusive of any flip function requested by Ekos.
4 years 10 months ago #39144

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A well designed mount will have hour angle axis movement limits, it will stop tracking, or any other movement, past the limits. Similarly for the declination axis.

Personally I see no need for an automated pier flip when an automated process is not running. The mount stops at it's soft limit.

ASCOM has a number of properties and methods associated with pointing state:
PierSide SideOfPier(); // normally get but can be set.
bool CanSetpierSide {get}
PierSide DestinationSideOfPier(rightAscension, Declination); // returns the pointing state that the mount will end up in if the slew to the specified position is done now.

Only a few mounts can do a flip early, one I know of is the Celestron GEMs, they have a Meridian Mode state which can be set so the mount will do a pier flip up to 20 degrees early, determined by the Ra limit settings. Once the mode is set a normal slew to the current position will do the flip. DestinationSideOfPier can be used to check if the pier flip will be successful and throw an exception if the pier flip will not happen.

One thing that is very useful in the automation application is to check that the flip really has happened and to retry at the next opportunity if it hasn't.
4 years 10 months ago #39146

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Well, then I guess my SkyWatcher HEQ5 is not a well designed mount since I have had more than one occasion where the meridian flip failed to initialize and the mount kept on tracking all night long. I was asleep at those moments and when I woke up next morning I found the telescope hanging at the lower side of the hour axis and still tracking. Fortunately it was pointing at a safe declination... I guess what I am trying to say is that it may not be wise to depend on these soft limits. Perhaps there is a way to check if the mount has soft limits and, if not, enforce a limit?

Anyway, as I wrote in an earlier comment, as long as it is possible to do an unattended meridian flip this is all fine by me.


Wouter
Last edit: 4 years 10 months ago by Wouter van Reeven.
4 years 10 months ago #39147

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Seems like nobody needs such a dialog - myself included.


The design idea is slightly different. The meridian flip behaviour is simply an attribute of the mount and not of a capture or schedule sequence. As long as you do not change the meridian flip behaviour, it remains the same for all your captures and schedules. I do not see a reason turning this behaviour on and off for specific sequences.

Yepp, this remains unchanged. The Mount module requests a meridian flip permission from the Capture module. As soon as a frame capture is completed, the Capture module grants the permission and waits, until the flip is completed. As soon as it is completed, it re-aligns and restarts guiding. By the way, this behaviour remains untouched.
4 years 10 months ago #39155

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Please accept my humble apologies. I did not intend criticism or disrespect with the statement.

Got it. Thank you for the clarification.
4 years 10 months ago #39158

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I also agree that the global control for meridian flip should only be located in the mount tab. Keep it simple.
Also, if it's not too off topic. Re:EQMod Target Pier side, when enabled areas of the sky become 'unreachable'. In that event it should ignore target pier side and slew normally.

Thanks all for all your hard work.
4 years 10 months ago #39168

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