This is my normal work screen, not that you should copy it, but it should give you somewhere to start.
Most important is the Histogram, I keep it at the top right. All these can be found to start with under Window on the top line. The histogram tells you about the photo, left is dark (black); right is light (white). The Histogram is split into 256 vertical columns, and in each is a vertical line representing the number of pixels found at that shade. Most astrophotographs are heavy with dark background so the histogram will likely be heavy on the left. The stars are likely to show towards the right. Keep an eye on it as you change things while processing.
Below it is a row of three items
Info. I usually only show the top half so I can see the number of pixels of which colour under the cursor on the photo. This depends on the Sample size. To see that click on the eyedropper tool to adjust it from point to 3x3 or 5x5 or a wider square. For background you should be trying to ensure the three colours are almost the same value. I try to get mine to 20,20,24 for red, green and blue. It also helps you find the nebulosity.
Adjustments is a means of making adjustments to the photo in a non-destructive manner, whereas the normal Curves and Levels etc. can be counted as destructive, in that if used their effect is permanent and to remove it you have to go back to a prior History state.
Channels refers to control over individual colour channels.
Below is History, Actions and Layers. Just for my convenience, I can get three items on a line, helps to use less space on the screen.
History is originally set at about 20 steps, which means that when you make the 21st change to your photo the first one is dumped. So I reset History, Edit/Preferences/History States to 200. This allows me to go back to see what I did earlier on.
Actions. I load Noel's Actions and Anne's Actions here, obtained from the internet. They both have to be bought, not costly though, and worth their weight in gold as good shortcuts to doing things.
Layers. Always available to quickly add or adjust layers.
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This is a work flow that you can follow in processing an astrophotograph. You can of course, add your own steps or miss out some of these. The actual photograph will dictate your course. It assumes you also have GradX and Noel's Actions in your PS toolbox. Don't overdo any step, be smooth and subtle.
Step
|
Action
|
Source
|
How to do it
|
Notes
|
1
|
Equalise
|
PS
|
Image/Adjustments/Equalise
then Crop the edges all round
|
To
see what you have in your photograph. Then turn it off and Crop edges to
clean up histogram
|
2
|
Levels
and Curves
|
PS
|
1.
Use levels to move black point to base of histogram
2.
Big stretch
3.
Contrast stretch
|
1. Don’t clip data
2. Usually only one big stretch (mild for
clusters)
3. Contrast stretch is “S” curve. Set points on curve for sky and
nebulosity. Pull sky down, nebulosity
up.
|
3
|
Soft
Colour Gradient Removal
|
Noel
C
|
Run
once
|
Use
for light pollution.
|
4
|
Gradient
Removal
|
XTerminator
|
First
Run:
1.
Lasso DSO, feather 20, invert
2.
Check balance background colours
3.
Run med/low
Second
Run:
1. Set Magic Wand Tool to tolerance of 35
2. Click in black area
3. Use Lasso with Alt key to remove DSO from
selection
4. Run fine/high
|
First
run includes entire image except DSO.
Second
run includes only black areas outside the DSO.
|
5
|
Set
B & W points
|
PS
|
Move
black and white sliders to capture spread data across entire histogram.
|
Be
careful not to clip; sometimes not necessary.
Some actions change histogram so may want to repeat this in later
steps.
|
6
|
Local
Contrast Enhancement
|
Noel
C
|
Run
action once
|
Not
on clusters
|
7
|
Enhance
DSO
|
Noel
C
|
Run
action once
|
Not
on clusters. This takes a while.
|
8
|
Cosmetic
Fixes
|
PS
|
Use
clone stamp tool or other PS tools
|
Remove
hot pixels, dust, etc.
|
9
|
Increase
Saturation
|
Three
options:
1Jay
GaBany method
2.
Noel’s Increase star colour
3.
PS hue/saturation
|
Run
Jay GaBany method as often as needed. It enhances the nebulosity without
bringing noise in.
|
For
galaxies, use Noel’s Increase Star colour instead, then PS Hue/Sat, increase
saturation by 20 or so
|
10
|
Increase
Star Colour
|
Noel
C
|
Run
action one or more times.
|
Complements
previous step
|
11
|
Levels
and Curves final
|
PS
|
Set
contrast with S curve
|
Check
black and whites points also
|
12
|
Noise
Reduction
|
Noise
Ninja (but it reduces colour),
Noel
C deep space or space noise reduction
|
Mask
out DSO, feather 20, invert
|
This
may change image and require reset of black/white points and image contrast
|
13
|
High
Pass sharpen, possibly 2 or 3 times with different radii
|
PS
|
Duplicate
layer, use HP on the top one, Blending mode – Overlay or less aggressive Softlight.
|
|
14
|
Less
Crunchy more fuzzy
|
Noel
C
|
Run
action once
|
To
taste
|
15
|
Final
check
|
Various
|
Repeat
of steps shown above as needed
|
Tweak
curves, check colour balance, maybe reset white point with eyedropper
|