How do I process my full disk photos
After processing the video with Avistack (1 min @ 30 fps / 8-bit, default settings) , let's start with the cropped RAW image. Avistack produces a 16 bit FIT image that has a very wide histogram range.
I usually process the image separating the proms from the disk, because there's no way to display all that range in 8 bits without suffering contrast loss or highly modifing the image with some tricky HDR toning.
I find that this is the most natural look, although the ring of fire effect is not present at the eyepiece, it's not that bad aesthetically.
The first step is creating a mask for the disk.
This is done by duplicating the image and adjusting the curves so that it produces a 2 color image: white for the disk, and black for the rest. It's better to apply some wavelets to produce a blur on the edge. This is going to produce a more pleasing image at the end.
The next step is create a mask only for the proms and the famous ring of fire.
The procedure is the same as above, but only choosing the high signal part of the proms, since this is going to be used to deconvolve the proms. Take care of not selecting the background, as this will increase the background noise.
And here comes the magic of Pixinsight, we are going to remove the disk from the proms mask with PixelMath.
Just apply this easy formula and the proms mask is ready!:
"proms mask" - "disk mask"
Now it's time to get some detail back in the disk. Apply the disk mask.
After spending too much hours with mainly every technique over there, I found that the most easy one is what works best: Restoration filter. It just works wonderfully with solar images.
You have to find the best parameters for your image scale / seeing, and it will remove all the avistack bluring. I usually do then a wavelet transform to enhance a bit the low scale contrast.
The next step is rather easy: play with the curves to give the masked disk the contrast you need. As usual, take care of not burning the highlights, and don't lose detail in the low lights.
The disk is ready!.
Now lets bring the shadow detail of the proms. Invert the disk mask (do not apply the proms mask yet). We are going to affect the other part of the image.
This is were I'm not being fair, since I'm modifying the image selectively. But this is a trade-off.
You have to apply curves until you wish. It's better to do various steps and avoid burning the proms.
Now let's do the final restoration. Apply the proms mask, that will do the trick without generating noise in the background. If the noise is there, you have to take care of the mask.
As usual, the parameters differ. Choose what's best for you.
If you like the images in color as I do, open the image in Photoshop and play with the color balance sliders. I usually do this:
+50 cyan -50 yellow in midtones
+50 cyan -50 yellow in shadows
And that's all, if you have any doubts, do not hesitate, and leave a comment!.