Re: Dec-Arc Tracking in APCC Pro v1.9 - an explainer please?


Dale Ghent
 

On Aug 19, 2021, at 09:06, W Hilmo <y.groups@hilmo.net> wrote:

Thanks for bringing this up. I was going to ask about this.

My ideal workflow with dec arc tracking and NINA would be to create a custom action that automatically invokes APPM to collect sample points along the declination arc of the object in the sequence. Off the top of my head, you'd really only need two parameters: The number of samples to collect, and the separation between two arcs on either side of the object's declination. This assumes that the object declination could be retrieved directly from the sequence.

That way, it could be pretty much automatic and just built into the sequence.
Yes, the target's coordinates can be retrieved by a plugin from the sequence. The plugin would just recurse back through whatever hierarchy of sequence instruction containers there are (it's akin to a linked list) until it encounters a DeepSkyObjectContainer, where it then reads the DeepSkyObject it has to get the target name/RA/Dec. I already do this to get that info in my Ground Station plugin[1], so that part is not an issue.

I'm thinking it would look like this:

Prerequisite, user-supplied settings:
1. General dec distance from target in D:M:S, or just decimal degrees (I personally find sexagesimal annoying) for placing two parallel arcs that bracket the target. So specifying a distance of 1.5 degrees would put two parallel arcs 1.5 degrees on either side of the target, which means the arcs have 3 degrees of separation from each other

2. Point density along those arcs. I'm thinking a good way to specify this would be in points per hour of RA? Is this too simplistic and there should be considerations to increase the point density closer to the horizon?

Execution:
1. Plugin is executed by the sequence as the first, or at least close to the first action, to do. There's likely little reason to faff about in a sequence before doing this.
2. The target's RA/dec is looked up and a point map file is generate using the user-supplied settings above
3. APPM is executed with the point map file being specified
4. APPM does the run and tells APCC to use the model file it generates when it's done
5. Plugin finishes execution and the rest of the sequence proceeds

Open questions for Ray:
1. How does APPM handle point map files that specify points that conflict with horizon limits? Will it attempt them regardless? Will it ignore any points that are below the horizon?

2. The point density question from above

3. I don't think I need to have any considerations for meridian limits when generating the CSV since I think those are automagically handled by APPM. Am I correct on that?

4. Anything else I'm missing?

Thanks!
/dale

[1] https://github.com/daleghent/nina-plugins/blob/main/GroundStation/Utilities.cs#L95

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