Hi!

I'm using a Losmandy G11, and have experienced something that I think is a bug in the side-of-pier identification by the driver. At least that is what Patrick Chevallier suggests in the longer discussion here:

groups.google.com/forum/#!topic/open-phd-guiding/s2TVIS3_K_Y

What happens is that the mount reports a shift in side-of-pier when I slew from southwest to northwest, as the mount crosses the azimuth 270 degrees. THis then causes PHD2 to run amok. As I get it, it is better if the driver uses hour angle.

I am relying on Patrick here. But the issue really causes troubles for my standard 20-variable job that crosses the 90 - 270- degree azimuth line several times.... and PHD2 runs amok.

I don't attach a log for the moment because I do not have one. But look at the discussion in the link for more details.

Best,

Magnus

Looking at the lx200gemini.cpp file it sends the ':Gm#' command and expects either 'E#' or 'W#' If that's changing as you describe then it's wrong and needs fixing in the mount code. That would be up to Losmandy. It doesn't seem to be in the driver.
Verbose driver logs showing what is going on after slews to the NW, NE, SW and SE would help to confirm this. They need to show the commands being sent to the mount and what is returned.

It might also be worth checking the version of the Losmandy code, perhaps there is an update.

Hi!

Thanks!!! Here is a log after preforming the following sequence, and with the reported side-of-pier (s-o-p): (MF means after a meridian flip)



I have little hope for a change in Gemini code, though. That is not something that happens frequently.... But Patrick Chevallier mentioned in the OpenPHD forum that perhaps the indi driver could use hour angle instead....? I'm not a coder, so I would not understand the consequences.

And the log file is the indi log. Kstars did not produce any log of this.

Magnus

Magnus,

Using the :Gm# command is the right way to do it.
A pier side simulation using the hour angle is only the last resort for mount that not implement it natively.

It can be interesting to see the result from the same test by other user.
But are you sure you use the latest firmware in the Gemini?

Patrick

Hi!

Stupid me, you are of course Patrick... sorry....

I just flashed the Gemini with latest firmware - however, I don't know if it is the one I already had. DO you want me to redo the log-file? A quick test shows me precisely the same behavior - going from SW to NW leads to shift side-of-pier.

Magnus

The INDI code is using the :Gm# command.
it's tricky because i don't have hour angle, just Ra, Dec and pier side. the time is seconds from start

There is a slew between 1410 and 1464 where the pier side reported changes from E to W but no evidence of a pier flip

Then a slew starting 1469, the pier side changes from W to E at 1488 and the dec increases to 89 deg, then decreases at 1493 which is evidence of a real flip with movement through the pole.
this slew finishes at 1548 because the Gv response change to T but there is no slewing to tracking message.
At 1549 another slew starts, this finishes at 1593 with no evidence of any pier side change.
1597 a slew starts. At 1616 the PS changes from E to W but no evidence this is a flip. It finishes at 1655.
Next slew start at 1657. At 1691 a pier side change but no evidence of a flip, the slew finishes at 1704.
1716 slew starts. 1727 pier side change, again no evidence of a flip, finshes at 1765. W
1769 PS W slew starts. 1804 PC W -> E 1823 mount flips through pole. 1875 slew finishes, no indi notification PS E
end of log

i'm not sure how to correlate this with what you report but it seems to me that the pier side reporting by the mount is sometimes wrong. It should only change as the mount goes through the pole, at a declination of 90, but it's changing at other times. This might be at hour angle 6 so the pier side is correct between hour angles -6 to 0 to +6 and incorrect from -12 to -6 and +6 to +12.

If that is the case then the problem might be hidden by swapping the pier side using the hour angle ranges where it is wrong. Or reporting the pier side as unknown. But who knows, maybe it isn't using hour angle.

Using hour angle directly isn't a good idea because it will be wrong when the mount tracks past the meridian.

I'm unsure whether this is the same issue. But my G-11 reports a change in pier side as soon as it crosses HA -00h 41m 00s, without actually performing a flip. The same occurs at +11h 19m 00s, regardless whether the mount is tracking or the user is slewing.

I did the very same test today and now it doesn't change side of pier anymore. Hell knows why. BTW, mine is a Level 4 V1.05 Gemini 1. If you want me to run tests, let me know what I should do.

Maybe it has been fixed by the firmware upgrade but it didn't take immediately, perhaps it needs some sort of hardware restart to load or initialise the new code.

There's very little I can do but the information needed is:
Slew to hour angles of -9h, -3h, +3h and +9h. read the pier side at each. They should be W, W, E, E.
If the pier side changes between -9 and -3 slew to a little less than -6h so the pier side is the same as the -3h value and wait for the mount to track through -6h hour angle. It should not change but then neither should it with slews.
Slew to just before the meridian, at an hour angle a little less than zero and a pier side of W->E. Allow the mount to track through the meridian. The pier side should not change no matter how far it tracks.
Once well past the meridian a slew to the current position should do a flip and the pier side should change from W to E.
It should behave similarly on the West, tracking through +6h.

Hi!

I'm not sure if you benefit from more info from me, but I did what you described in your post - slewed through hour angles and noted the side-of-pier - in the logfile. What I noted:
Then I slewed to just before +6 hours and let it track trough the 6-hour mark. It did not change side-of-pier precisely at 5h but close.

Does this help?

Magnus

It took me a while to figure this flip thing out. I hope I got it. I've set the Gemini "Set Go To:" parameter to 90 and Ekos' "Flip if HA>" to 1 degree (4 minutes).

I cold started Gemini, started Ekos and found the pier side changes at HA -06h00m00s. It's WpE at -05h and EpW at -07h. (This is what I would expect, no?) [Ah, forgot to mention it changes pier side regardless of tracking or slewing]


That's what happened. 4 Minutes appears a bit tight. Occasionally the mount tracked through the meridian and 4 minutes later a slew was initiated. However, the mount barely moved, did not perform a flip but instead was set to a position slightly before the meridian again (like 6 minutes back to -00h02m). It then tracked past the meridian again and the next slew at 00h04m actually made the mount flip.

To be clear: are you not talking about another issue than the one I am? You seem to be talking about challenges of making the mount flip, that is, the side-of-pier shift that should be there, and when the mount should flip.

My issue is a shift of side-of-pier in a very different situation - when a flip should definitely not be initated. Not anywhere near the meridian. My unwanted side-of-pier changes makes PHD2 run amok with the mount.

Or....?

Magnus