Just double-checking that I've got this right. I'd like to expedite my LRGB acquisition, interleaving the subs for each channel more to ensure that, on a given night, I wind up with roughly equivalent integration time on each. So the strategy is:
Autofocus Luminance. Note the position. Repeat for R, G, and B.
From the Filter drop-down, check "autofocus" for Luminance. For the other three channels, uncheck "autofocus" enter the difference between L and each other channel as "offset".
Start my acquisition session with Luminance, and thus autofocus.
When the filter switches, the offset should be applied to get it pretty close to perfect focus.
I figure that if the L is spot-on, I don't have to be OCD about RGB, since the eye picks up detail mostly in luminance. Without pausing to autofocus R, G, and B, it costs me very little imaging time to switch filters, and so I can afford to do so much more often. If I run, say, 25 L and 5 each RGB, I'm autofocusing every 20 minutes with my customary 30-second exposures for star color, so when the clouds roll in I'll have a balanced set of data. (Or is it better to set them all to "offset" with L=0, focus initially with L, and just tell Ekos to refocus every N minutes?)
This would be especially helpful for mosaics; since slewing and solving is so quick on the Pi 4, I might even extend the technique to cycle repeatedly around the whole mosaic FOV instead of doing one bit at a time and dealing with the subsequent background normalization and other problems between panels.
You should perform 3 focus routines and record the average of the three sessions. Do this for all four filters.
I also suggest you do not do three Lums back to back, and then three reds etc, but instead do all four filters (L,R,G,, record their values, and then do that again x 2. This will help ensure any changes in temp during this process don't skew the values from the first thee Lums are not too far off from the last set of blue filter focus values.
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