Processing with Photoshop

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 3×3 or 5×5 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.

——————————————————————————————

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.

Copyright © 2018 Doncaster Astronomical Society. Registered Charity No: 1091486