Add the field derotation support

[Jungshik Shin]

I have a Falcon Pegasus rotator to use with my Dobsonian (Orion XT10G). NINA supports it well for the rotation.

This FR is to ask for the field de-rotation support. Currently, I use a separate program by Falcon to turn on and off the field de-rotation. If it can be implemented inside NINA, I wouldn’t have to rely on that program for the field de-rotation (Alt-Az mount).

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Thank you

[Jungshik Shin]

A rthread at the CN is https://www.cloudynights.com/topic/907204-zwo-rotator-any-news/#entry13217546

[Stefan B]

Hey - thank you for the suggestion.

The ASCOM interface for Rotators that N.I.N.A. uses, currently does not support this directly. I have however sent a query to Pegasus if it would be possible to enhance the ASCOM driver to support this via the “DeviceActions” construct. Then the “Device Actions & Commands” Plugin could be used to utilize them.

Adding field rotation directly to N.I.N.A. will take more effort if this option would not be feasible. Most likely it isn’t possible via the ASCOM interface at all in a generic way, as this would require sending steps per second to a rotator, which is not possible.

[Jungshik Shin]

Thanks a lot for the reply, Stefan !

I’m also grateful that you contacted Falcon about the possibility. I hope they can offer something (late if not now).

Just in case you haven’t seen this, this does not seem to have been resolved in Indi, either. See https://www.indilib.org/forum/stellarmate/11180-pegasus-falcon-question.html .

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[Dale Ghent]

The ability for a rotator to do this can also require firmware changes in the rotator itself to support the necessary logic to control the motors, and the motors must be able to creep along at the desired rate. So it is not entirely a question of a missing implementation in software as there are hardware requirements, as well. On the software side, the rotator driver would need to know the tracking rate of of the mount in order to derotate at the correct rate and, with mounts that use sky models, the tracking rate can vary from moment to moment, thus the rotator’s rate would have to as well. It can be complex. This is why alt-az systems which are designed with de-rotating rotators are usually integrated tightly with the mount. For amateur-grade systems, my advice is to just get an equatorial mount.

[Stefan B]

Pegasus is looking at the plugin framework and might be interested in providing native drivers for their devices.
This would make it possible to add such a derotation feature as well. I have however no confirmation or timeline for this yet.

[Jungshik Shin]

Thank you, Stefan, for looking into this.

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To Dale, the hardware support is already present in the Pegasus falcon rotator. Otherwise, a separate program provided by Pegasus would not be able to de-rotate my Dobsonian. It works pretty well.

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As for equatorial mount, I do have one for a refractor and have been using it for quite a while. In the meantime, I want to use my Dobs for small DSOs like galaxies.