Target Lost and Runaway guiding after Meridian Flip

[ShaunO ZS1RA]

Hi,

As I track a target across the sky my mount guides beautifully with a total rms error 0.4

When the mount flips the target is no longer in the FOV of the guide camera and obviously the guide star is then lost. A second problem is that I have to recalibrate PHD2 when I flip otherwise the mount will just run off. My immediate thought was that my Polar Alignment is too far off. I checked it with the Guiding Assistant routine in PHD2 and it gives me a PA error of 4 arcmins which I think should be good enough. Is it? As for the mount running off after the Meridian Flip I have tried several permutations of checking/unchecking the Reverse Dec and RA after MF in both Sitech and PHD2 without any luck. PHD2 will not guide my mount unless I calibrate whenever I cross the Meridian. When I do calibrate it will happily guide for a long time.

I would really appreciate some help with this.

Thanks
shaun

[ShaunO ZS1RA]

Here is the link to the log files. https://openphdguiding.org/logs/dl/PHD2_logs_kqyt.zip

Thanks

[bw_msgboard]

It looks like you've been chasing your tail here.  To begin, the fact that your target is no longer framed after a meridian flip is pretty common, obviously nothing to do with PHD2.  The most common techniques for dealing with this are 1) build a pointing model for the scope to improve the go-to accuracy and 2) use plate-solving to center your target after any slew. 

 

To straighten out the meridian flip problem, you need to start by setting the Sitech options the way they should be and then leave them alone.  It would be better to not have the Sitech controller trying to change things based on side-of-piier, I would disable that.  Once you've done that, leave those mount settings alone.  On the PHD2 side, start by reading the manual on the 'Reverse Dec output after meridian flip' topic.  It doesn't work the way you think it does, it doesn't "fix" your immediate problem.  Since you're having trouble with this, I recommend that you use the Meridian Flip Calibration tool:

 

1) Point scope close to celestial equator on either the west or east side of pier.  It doesn't need to be close to the meridian

2) Connect equipment in PHD2

3) Start looping, make sure you have a star to work with

4) Start the Meridian Flip calibration tool.  It will automatically do a calibration for you when you say you're ready

5) When the calibration completes, manually SLEW the telescope to the other side of the pier, pointing somewhere near the celestial equator. It doesn't have to be close to the meridian and it won't be pointing in the same area you were using before.  Leave the Meridian Flip tool running, it is trying to march you through the process and it will be waiting for input from you at various stages.

6) Start looping, make sure you have a star to work with

7) Tell the Meridian Flip tool that you're ready to proceed and let it do another calibration for you.

8) Once the wizard has completed and the option is set appropriately for you, leave it alone, don't fiddle with it in the PHD2 Advanced Settings dialog.

 

Good luck,

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of ShaunO ZS1RA
Sent: Sunday, October 24, 2021 12:55 AM
To: Open PHD Guiding
Subject: [open-phd-guiding] Re: Target Lost and Runaway guiding after Meridian Flip

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[ShaunO ZS1RA]

Thanks so much Bruce, this is very helpful.

As you may have seen from my log I attempted to do the Meridian Calibration but was unsure how to proceed. Obviously the weather is bad, this because I want to get outside and implement your suggestions :-D

When you say "better to not have the Sitech controller trying to change things based on side-of-pier," I am assuming you are suggesting that I disable these options as highlighted in the picture.

I should then run the Meridian Calibration routine and it will then automatically check or uncheck the field in pic below

Thanks once again for your assistance.

shaun

[bw_msgboard]

Yes, you should disable the two checkboxes in the Sitech controller that you've highlighted.  Otherwise you have too many cooks in the kitchen.  And yes, if you work your way through the Calibrate Meridian flip wizard, it will set that property for you.  Just do exactly what the wizard says, don't try to take shortcuts or otherwise "optimize" the process.  I've seen a case where someone wrestled with this for two months before getting it right - something I still can't understand. 

 

Good luck,

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of ShaunO ZS1RA

Sent: Sunday, October 24, 2021 10:17 AM
To: Open PHD Guiding
Subject: Re: [open-phd-guiding] Re: Target Lost and Runaway guiding after Meridian Flip

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/69aa5688-0626-4c14-bb45-8967c7fde9ban%40googlegroups.com.

[ShaunO ZS1RA]

Thanks Bruce,

I’ve done as you suggested and it irks perfectly.

Shaun