People are asking me, so I am going to put up the GHS stretch steps for this very explicitly as it is a good example of a very dim object enhanced with GHS.
My original image was 7h with the CCD:
Sh2 181 Another Faint Sharpless2 Object Here are the steps to using GHS with this dim target now down to 51m acquisition:
Step 1:
Take the dim Ha and apply noise and star removal (see history explorer)
Use the 250% Zoom to the linear Ha image so you can see the now narrow histogram and put the symmetry point at the middle of the now very narrow peak.
Step 2:Send the symmetry point and see how you now have the "S" curve on top of the linear peak.
Increase the Stretch Factor until you see something in the preview.... in this case I did not have to modify "b" but you may have to to optimize
APPLY this to the image
Step 3:Reset the Zoom to 1 and you will now see a normal histogram for final adjustments... the dark point and maybe "b" will move the histogram back and forth left to right as the "S" intensity changes.
Step 4:Reset GHS in lower right corner
Change the Transformation to Linear
Click the button to the right of Low Clip to set the bottom of the blacks... move the histogram to the left
APPLY this also
Step 5:Last step put the symmetry point at the top of what every histogram you want to "S" curve in the now stretched image... could vary in color image
Note you have done the main work but you need a Stretch for the "b" to work
There is the "dim" Sh2 181.
APPLY this final tweak also.
Hope this is of some help with the essentials.
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