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

Bi-monthly release with minor bug fixes and improvements

Problem syncing a dome to a scope (MaxDome II INDI driver indi_maxdomeii)

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Thank you for your reply Ferran - the results of my test is;
0). with the dome Meridian Side control set to "nothing " ie: netter East or West selected - I assume this is "auto"
1). Mount at 0" DEC and the OTA in the West (counterweight bar horizontal with the weights in the east), the dome slewed to 325 or so as expected! Result!
2). Mount "flipped" with the OTA pointing north but this time on the eastern side of the pier and the counterweights on the west, the dome slaves to 318 degrees or so - again Meridian side side to auto
*** the aperture is NOT in the right location, it is missing the OTA by some 90" or so by the look
3). If I change the OTA offset to be 0 meters then it reverts to roughly 360" as expected - this was a simple test to make sure there wasn't another bug
4). If I set the mount asset to -.45 (NEGATIVE) then the dome slews to 34" - amazing! (I through the code ignored a negative OTA offset?)
5). If I manually intervene and set the Meridian side in the Dome Control Panel to East, the dome slews to 34"
6). I get a big bottle of red wine, sit down and cry :-)

I assume this is a "pier side sniffing" problem, or something else?
3 years 6 months ago #59241

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Hi Paul,
I’m following this discussion and all the troubles you’ve got : you get all my sympathy because I got all these troubles too.
I finally found a solution after two steps .
1/ CAREFULLY POLAR ALIGN YOUR SCOPE. This is THE basis to get a good sync scope-dome.
I think that your polar alignment is far from good enough.
2/ The most important dome params are the N displacement and the E displacement
The third most important param is the park position angle. Verify this.
Each time you change the polar alignment you should check the dome params.
Chris ROLAND gave a good guide line to define them empirically :
www.indilib.org/forum/general/7125-probl...maxdomeii.html#55264
Now my dome syncs perfectly with my scope
Oh by the way, the big bottle of red wine will not help !
The following user(s) said Thank You: Paul Muller
3 years 6 months ago #59242

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If the mount pier side is reported incorrectly then there's little to be done, garbage in, garbage out. i don't know if there is a prospect of correcting this in the INDI driver, maybe looking at other parameters. It will almost certainly need to be managed on a mount by mount basis.

The SB ASCOM driver is the only one which I have formally withdrawn support from because it was so inconsistent and varied so much depending on the mount and unnotified SB software changes.

As for the Z position, yes I glossed over this because I don't see a good way to check this. The dome slit is vertical so shifting he mount up and down won't make much difference. The position where Z will have the most effect is looking East or West because this is where the mount hour angle axis tilt WRT the dome azimuth is greatest. This seems to mean that the NS offset and the Z offset will be to some extent interdependent.

Come to think of it the NS offset could be set by having the mount with an hour angle of 0 or 12h, the counterweight shaft horizontal, and the scope looking exactly vertically up. If the NS offset is zero the dome azimuth should be 90 or 270 and shifted towards the N or S if the offset is N or S. This will be insensitive to the Z offset.
Ten set the mount with an Ha of +6h or -6h and dec 0 so it's looking at the E or W horizon and adjust the Z axis.

BTW I don't think there is a requirement that this is done at night. A permament observatory should already be polar aligned and pointing to within a fraction of a degree should be possible simply by using index switches or marks and a quick align. Dome positioning should only be needed to the degree. Maybe a single star alignment on the Sun. First magnitude stars and the major planets can also be visible through a scope in daylight.
The following user(s) said Thank You: Paul Muller
Last edit: 3 years 6 months ago by Chris Rowland.
3 years 6 months ago #59244

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Thanks for the words of sympathy JCJ - I really need it I think!

1. I am pretty confident that my mount is superbly polar aligned, as in a few arc seconds off - the TPoint model for my Paramount is reporting a 12 arc second pointing accuracy and that typically requires a very accurate polar alignment - so I am 99.999% confident that it's not it. But I've learned never to say never!

My tracking/guiding is under 0.7-0.9 arc second peak to peak RMS over a 6 hour window - again I get the feeling I would be seeing larger variations if I was far enough off PA to cause the azimuth to be so egregiously wrong.

2. Chris has given the world of dome management a great gift - I will need to work with him to write it up - just need to figure out what vector is impacted but eh Z axis :-)

The red wine is looking more tempting - so is golf!
3 years 6 months ago #59247

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Thanks Chris - you're THAT Chris Rowland - wow! (bows deeply)

My fears are starting to come true. One more reason to ditch the Paramount (which is otherwise quite amazing) and look at something with a beefy payload and is remote/robotic ready (this whole setup moves 1000km away as soon as lockdown is over.

I'll do some more digging around to see if there's an API call that might give us more certainty - to be honest I would have thought that the minute the mount gets beyond a certain RA that it would be obvious which side of the meridian we're on, but I have not spent enough time thinking about the math for that to be more than a wild ass statement.

Is now a good time to bring up my old Apogeee AP6EP (the parallel port model) that I have a not so secret desire to get working under INDI - 24u pixels go so nicely with a 3000mm+ FL and I would hate to see a lovely old piece of equipment get thrown out!
3 years 6 months ago #59248

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re: your BTW, I do most of the testing during the day if I get a chance, it's only down to trying to weave the hobby between work and play that forces things into teh wee hours (oh and that person who apparently I share a house with, keeps muttering something about "you love that bloody telescope more than you love me" or something - it's hard to hear her properly inside the dome, so not 100% sure ;-)
3 years 6 months ago #59251

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I've seen so many people moaning that doing this sort of set up and testing has wasted hours of precious imaging time...

The mount property that defines pier side is actually the declination axis position. For one pier side the axis position is in the range -90 to 0 to +90 and in the other +90 to 180 to 270/-90.
If you are at a dec of -30 and do a pier flip the hour angle axis moves through 180 degrees and the dec axis from -30 to +90 to 210 for the Northern hemisphere or -30 to -90/270 to 210 in the south. The mount alignment model sorts all this out to give you Ra and Dec.

You can't use Ha because if you track through the zenith the Ha goes from -ve to 0 to +ve (or just under +12h to +12/-12h to just over -12h) The pier side does not change. Really pier side is a poor name, pointing state would be better.

Some mounts also change "pier side" around + or - 6h hour angle, this makes things OK to the N or S but very worng if you move between the two. There's one driver that uses Ha for the -4h to -9h and +4h to +9h range, the mount reported pier side close to 0 and +-12h except for declinations close to 90 where it reports unknown.
The following user(s) said Thank You: Paul Muller
3 years 6 months ago #59264

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When you're next in Australia or I'm wherever you are (UK)? I'm buying you a drink - the first and only time I've seen someone document pier side in a way that makes sense "The pier side does not change. Really pier side is a poor name, pointing state would be better." Explains why I've never been able to wrap my head around it!

Thanks Chris.

I'll dig around and see if there's a way to get the meridian side information out of TSX - I assume the Alt/Az position results from www.bisque.com/wp-content/scripttheskyx/...2b4a030fc235df42cab3 aren't helpful?
3 years 6 months ago #59270

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With that problem apparently identified (and while it seems unlikely that Im the only person running a Paramount in a dome and am the first to hit this issue), I am wondering for the sake of completeness do I log it as a defect/bug in the INDI Github- if for not other reason than to help other poor fools like me avoid days (weeks) of fruitless pain trying to fix an impossible situation?

I've had a quick look at the TSX API and the good news is that I should be able to write/map the dome proxy between the two systems and keep my dome under the control of INDI provided that I treat it as a Roll-on/Roll-off in INDI (open, close, park, etc) and leave TSX to manage the dome slaving and actual hardware management.

IT does slightly bugger up my plans as I had hoped to be able to cable the mount/OTA with only an Ethernet and a power feed with the dome and flat fielder being controlled by the second "dome" RPi INDI device server over WiFi but unless I am mistaken (happens a lot), I will need to run the USB cable back to the NexDome controller from the OTA computer.

Thanks for all your help everyone who chipped in - I'll put the million monkeys back into the typing pool, they've got the complete works of Bill Shakespeare to crank out and the universe ain't getting any younger...
3 years 6 months ago #59274

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