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Guiding lost after meridian flip

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#1 kyle528

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Posted 23 April 2019 - 06:08 AM

Things last night were going pretty smooth, all up until the flip. I was doing sub 1” according to phd2, crystal clear, incredible seeing. My flip was right on time, a couple degrees off which a go to took care of. The real problem came when I went to start guiding again. Nothing but problems. First, it seems like guiding us going well, all is normal, then all of a sudden about 30 seconds into guiding dec just drifts wildly off course several degrees if I let it go long enough). I restart guiding and the same thing happens, always after a few seconds of what looks like good guiding. I end up restarting phd2 and then it does. The exact same thing.... but now in RA??? Dec guides fine, then RA is wildly spinning out of control. From 1.5” guiding to out by a degree. Restart phd2 again. Guides fine for one 4 minute exposure, then back to the same problem with dec. at this point in the night I’ve wasted enough time, and need to sleep, so that’s when I gave up on it. Has anyone had problems like this before? Was it caused by the meridian flip?


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#2 pyrasanth

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Posted 23 April 2019 - 06:28 AM

I had a similar problem with PHD2 a few years back. The cause was a setting that had not been ticked which reverses the guiding direction after a flip. Some mounts need this and some don't. If it worked before after a flip with no issues them something unknown has changed.

 

A solution I found, and not the best, until I found the setting, was to run a new calibration after the flip but that takes a bit of time.

 

I would explore on the PHD2 forum where the issue could lie.

 

Good luck with getting this resolved.



#3 Dynan

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Posted 23 April 2019 - 07:05 AM

Did you shift counterweight to 'Heavy East'?



#4 kyle528

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Posted 23 April 2019 - 09:29 AM

Did you shift counterweight to 'Heavy East'?


Yes. No change


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#5 StephenW

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Posted 23 April 2019 - 10:22 AM

What mount are you using and how are you connected to it (ASCOM, ST4?).



#6 kyle528

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Posted 23 April 2019 - 10:36 AM

What mount are you using and how are you connected to it (ASCOM, ST4?).


I’m using a CEM25, and was connected via ST4 with “on camera” setting in PhD2. I started the night out connected via ascom/hand controller with a usb/serial connection but guiding would stop randomly and PhD gave me the notification to check my cables. After switching to st4 “on camera” I was guiding flawlessly until after the flip.


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#7 OldManSky

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Posted 23 April 2019 - 10:40 AM

pyrasanth above is correct -- using PHD2 with the CEM25, you *must* check the setting to reverse direction after a flip.  If you don't, it'll do exactly what you've experienced.

I learned that one the hard way, too.  Going to the other side of the mount (east to west or west to east), guiding would go nuts.

Once I ticked that checkbox, everything worked fine.



#8 StephenW

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Posted 23 April 2019 - 11:03 AM

>After switching to st4 “on camera” I was guiding flawlessly until after the flip.

 

Yep, as others have pointed out, when using the ST4 interface, PHD2 doesn't know which side of the meridian the mount is on so you have to explicitly tell it to switch guiding output after the flip has occurred.


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