The Fourth of July

07/04/2024. Turns out that on every Fourth of July lately, I've habitually made a Facebook post featuring a spectacular, colorized solar photo and some remark about fireworks. That worked especially well today.

Click any image to see it better.

I have so many variations of today's top subject. Coronal loops change very quickly -- these erupted, took shape, and thinned out over the course of an hour or so -- and they respond well to many different treatments, including the foreground, excluding it, etc, etc.

 

Same clip, different treatment.

 

It turns out that the very best results were gamma off, exposed right down the middle of the histogram. That gives enough light for good detail above the rim and retains "shadow" detail below it as well. Gamma adjustments can improve one or the other, but not as much as the preview in FireCapture might lead a sweaty, hurried, hassled observer to expect. Here's a gamma-off stack of the approaching rim:

 

A two-panel image of the receding rim features its own charms:

I've adopted a 12-panel workflow (with some help from Photoshop's batch facility and a couple of custom actions I've put together to assist with imperfect flats). There's still some adjusting to do. For example, sometimes I need to crop the edges of the stacked data. More experiments, more practice...

 

07/05/2024. Today's first efforts: systematic mosaic trials. First, a 12-panel mosaic, gamma off, then a 10-panel effort with strong gamma (14), and finally another 12-panel effort at the same strong gamma setting.

Tracking was very good today, so there is little difference between crop and expand modes in AS!4, but crop ought to work better for this in theory (no black borders), so I've used it. I also tried a 10-panel merge (two-across at the extremes, three-across in the middle) which worked nicely. Mosaics captured with strong gamma do seem to align better. And this time at least, the expanded panels aligned without drama while the cropped ones required some intervention (I assume owing to the reduced overlap, but that's a guess). Here's an unassisted mosaic of 12 full-frame stacks straight from AS!4 w/o further adjustment. Voila!

The technical summary: Gamma 12, expand panels in AS!4. Best 103 of 500 frames times 12. In Photoshop: "Photomerge" all panels, flatten layers, apply "Solar Suite One" action, USM, High Pass with USM applied to the HP layer, then blended with the previously processed image. The odd number of frames (103) is so I could tell which panels were built using what options. I store the log files, so now I know where to look for details since AS!4 will write stacks and logs into a folder named for the number of frames selected. I ask for 99, 101, 102, 103 etc as a housekeeping ploy.

Under a cloudless sky with occasionally excellent seeing (so steady that sometimes I had to check: is this thing on? nothing seems to be moving), I couldn't resist some tall stacks of interesting areas. We'll see if any are photogenic (oddly, not really). I might pick a couple to go here by and by, but I'm not particularly excited by them, and haven't I used enough bandwidth today?

 

 

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