Transfer manual rotation settings to PHD2

[David Jardine]

Hi,

I use NINA for my astrophotography and I use the manual rotator function in NINA to tell me how far to rotate the camera for the desired framing. (For more details, see: https://youtu.be/rwpOO7CsD7U)

Unfortunately, the manual rotation information is not passed from NINA to PHD2. Because I use an OAG which rotates with the camera, I must recalibrate PHD2 whenever I rotate the camera. I am aware of a discussion about the use of the ASCOM rotator simulator to pass along manually entered rotation information to PHD2 so that recalibration is not necessary. (https://groups.google.com/g/open-phd-guiding/c/ilcIkO8vnVw)  I would like to try this; however, I cannot find any online documentation of the implementation of this arrangement.

Assuming that I already have a good PHD2 calibration and that I have set up the ASCOM rotator simulator as a device in PHD2, I plan to do the following:

1)    Start with the camera in the position (rotation) that was used to create the PHD2 calibration.

2)    Use NINA’s manual rotator function in conjunction with NINA’s framing assistant to generate the rotation information necessary to properly frame the target. Record the size and direction of the rotation. Manually rotate the camera.

3)    Enter this information into the ASCOM rotator simulator. Click “Move” so that this information is transferred to PHD2 to adjust the calibration.

My understanding is that if I have done everything correctly, PHD2 will modify the calibration so that it will work for the new rotation. Can you see anything that will  prevent this from functioning?  I know this process may sound a bit awkward, but I think that it would be faster than recalibrating PHD2 each time I rotate the camera.

Assuming that this process functions properly (and that's a big if), I have a couple of additional questions:

1)    For purposes of testing this process, what amount of rotational discrepancy between the orientation of the PHD2 calibration and the orientation of the camera sensor is likely to produce the most easily observable changes in tracking (60º, 90º, some other number)? This information will help me to test my system so that I can determine if my approach is working or failing.

2)    If I select the “Auto restore calibration” option (Advanced settings --> Guiding), will this restore the (original) calibration settings that preceded the rotation, or will it restore the calibration settings that were modified at the time of the last used rotation?

I hope this makes sense. I have really enjoyed PHD2 and have been amazed by the excellent quality guiding that it provides. Thank you for all of your work on this wonderful program.

David

[Bruce Waddington]

Hi David.  This is a good plan and should work for you,  it's actually how we test the rotator functions during development.  The only question is whether the "reverse sign of angle" option needs to be checked in the 'Other Devices' tab of Advanced Settings.  That will depend on whether NINA adheres to the ASCOM sign convention for rotation angles.  The important thing is to not get into a wrestling match with the software and try to over-think things or take shortcuts.  Along those lines, I recommend a different approach to your experiment:

1.  Start at a rotator angle of zero for both NINA and the ASCOM rotator simulator

2.  Do a PHD2 calibration

3.   Quickly confirm that guiding is working ok, then stop guiding

4.   Use the NINA manual rotator machinery and force it to choose a rotation of about 45 degrees then move your manual rotator accordingly.

5.   Enter 45 degrees into the ASCOM rotator simulator

6.   Start guiding again and see what you get.  If things look fine, you're golden.  If not, do this:

7.  Restore things back to the zero point in both NINA, the ASCOM rotator simulator, and your manual rotator

8.   Flip the setting of 'reverse sign of angle' in the Advanced Settings

9.   Repeat the PHD2 calibration in this 0 rotation position

10.  Repeat steps 4-6 above

I have recently seen a very experienced imager fight with this for weeks by not being rigorous about all this.  If it happens that NINA also has a "reverse" choice, it's critical that you choose the option in only place - either in NINA or in PHD2, not both.

Under the hood, every PHD2 calibration records the rotator position at the time the calibration is done.  Going forward, as the rotator is moved around, the calibration is always adjusted based on the original calibration position and the current position. 

Thanks for the kind words on the product and I hope you continue to get good results from it.  If you run into trouble, let us know.

Regards

Bruce

[David Jardine]

Hi Bruce,

I appreciate your suggestions. I will implement them as soon as we have a (rare) clear night during our wet Pacific Northwest winter. I looked at the PHD2 profile files (*.phd) and had a brief look through the calibration settings. I will watch the /scope/calibration/rotatorAngle and the /rotator/LastMenuChoice lines. It will be interesting to see what they do when I experiment with the settings.

Do you think that I could approach this problem using the ASCOM simulators? While I recognize that real world testing cannot be bypassed, this might help me to better understand the issues so that I can make more efficient use of a clear night when it arrives. If this problem is amenable to simulation, are you aware of a tutorial that discusses how to use the ASCOM simulators with PHD2? A while back, I spent a short time trying this, but was not completely successful and decided to move on to other projects.

Thanks for the help.

David

[Bruce Waddington]

Hi David.  You don’t need to grub around in files to see how PHD2 is interacting with the rotator.  If you use the ‘Review Calibration’ pull-down menu, the rotator position at the time of calibration is shown along with other info about the scope’s pointing position.  The ‘Stats’ window shows the current position of the rotator during guiding if one is connected.  I just looked at the NINA documentation and can see what they’re doing when there’s no electronic rotator on the scope.  All you have to figure out is which way to rotate the camera – when the NINA tool says rotate 40 degrees, are you going to rotate it clockwise or counter-clockwise?  The ASCOM specification says that rotation should be done counter-clockwise against the sky but I don’t know if that’s how NINA presents the info.  That’s really the only thing you have to figure out – if it’s backwards, change the ‘reverse’ setting in PHD2.

 

I don’t think the simulators would help you much.  This stuff all works within PHD2, as I said, it’s really only a question of figuring out the direction of orientation coming from the NINA tool.  You might be able to ask on the NINA forum and get an answer ahead of time.

 

Good luck,

Bruce

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