Re: Anyone using Orbitals plug in for NINA to track comets using AP mount via APCC

Dale Ghent

I'm not the author of the Orbitals plugin, but George Hilios is availble on the NINA Discord chat as are many users of it. Plugin authors also post notices of updates there, well.

The intention of the Orbitals plugin is to give you the ability to track non-sidereal local objects - comets, planets, asteroids, etc. instead of tracking the star field at sidereal/king rates as per the norm. To do this, Orbitals calculates the object's rate of shift for both RA and declination using the data available for the object in the minor planets database. It then sets a custom tracking rate for both axes on the mount. If a guiding app is being used, it also sets this rate of RA+dec shift in the guider so that it also tracks the object and doesn't try to correct, and thus fight, the custom tracking rate of the mount. I *think* PHD2 is the only guiding app that NINA supports that offers this capability, as PHD2 has it for its own comet tracking mode. I believe the shift rate is measured in arcseconds/hour.

At any rate (ha ha), this comet would require the use of the Orbital Object Sequence container in the Advanced Sequencer. You'd fill in your usual sequence items there, but also add the Set Shift Rate instruction and trigger, found in the Guider section of the list of instructions. The Set Shift Rate instruction starts off your imaging with the correct custom tracking rates, and the Set Shift Rate trigger updates the mount (and guider, if you're using PHD2) between exposures. Normally, you'd have that imaging running inside its own loop within the Orbitals Object container.

You will also notice a Stop Shift Rate instruction. This lets you stop the custom shift rate where the camera tracks the comet, and revert to sidereal where you track the star field. This allows you to do both common styles of comet/asteroid imaging - one where you track the comet and the background stars are streaked, the other with the stars not moving, with the comet moving across the star field.

The plugin will, by default, center the object in the frame but new versions of the plugin allow you to set an offset, if you'd prefer to stick the nucleus in a corner of the frame with the tail extending across it.

On Jan 28, 2023, at 03:31, Jim Fakatselis <pashasdad@...> wrote:

Has anyone on this list successfully used the NINA Orbitals plugin to accurately track C/2022 E3 ZTF?

I'm getting very poor results with Orbitals, how ER, when using Horizons through APCC all works as advertised, thank you Ray!
Was wondering if it’s my error with Orbitals or something else.
Thanks for any insight by anyone.

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