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Stretching
Stretching
Normally, I'd tweak the screen stretch and apply it using HT, but this data requires something more involved. The nebula in the Ha and OIII masters is extremely bright and could lead lead to washed-out colors later on. Let's stretch the dimmer parts of the nebula more than the core
First, I darken the screen stretch considerably by zooming in on the top bar in the STF window and moving the midtones slider to the right, then apply it.
Now I use the GAME script to create a mask, blurring the edges using a couple hits of the Convolution Process
We will use the mask to prevent the nebula core from brightening too much during our next stretch. To do that, we'll invert the mask and use Curves to lighten it. The dark part of the mask will reduce the effect of the stretching.
This is a tip from Adam Block's recent video on processing the Rosette.
Next we drag the mask onto the Ha master.
After one stretch with the mask in place. Notice how the background has been brightened without much brightening of the nebula core.
Brighten the background by moving the midtones to the left.
Ha - we're there after two stretches. I tried to leave the Ha background a bit brighter than OIII or SII because I want the Ha signal to dominate the shadows.
OIII after stretching.
SII after stretching.
RGB stars.
Importing Into Photoshop
Importing Into Photoshop
After saving the files as 16-bit Tiffs we close Pixinsight. Just like the Witch Head example, we'll load our files as a stack into Photoshop and arrange them as seen here.
Again, I will follow Craig Stock's Photoshop workflow from his YouTube tutorials. We'll put each layer into its own layer group, and add levels and hue/saturation adjustment layers to each.
I want to create an HOO image first and then add the SII data in the highlights. To do that I'll colorize the Ha to Red (0) and the OIII to 180 (cyan, as if we added the OIII in two separate blue and green layers). I'll turn off the SII and Stars for now.
Hue/Sat. layer in colorize mode for OIII. 180 is halfway between green (120) and blue (240).
Hue/Sat. Layer in colorize mode for Ha. Red is 0.
The layer groups. Every layer group is in Screen blending mode except for SII. Stars and SII are turned off so I can work with the HOO combo first.
Ha and OIII combined to make an HOO image. I haven't adjusted anything using levels, yet. The next step is to tweak this image and then add SII.
On the next page we'll add the SII data.
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