John it sounds like you got the hang of it now, but I'm finally back home and I've attached my NINA Advanced Sequencer Dawn SkyFlats template in case anyone else wants to try it out. This works flawlessly for my ~f/5 Newt and G11G, but the sun angle will have to be tweaked for each setup... faster f/ratios will have to be triggered when the sun is a little lower and slower f/ratios when the sun is a little higher.
This template takes my RGB flats (I don't shoot Lum) about 18 minutes prior to sunrise and my SHO flats about 3 minutes after sunrise.?
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All one needs to do is copy the template into their "Sequencer Templates" folder as defined by NINA settings on the Options > Imaging > Sequence section
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Let us know when you get it working the way you want it.
Ryan Noonan