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Digitally Enhancing Astrophotos

Saturn 


After repeating the stacking process used in the beginning, we start out with 
the stacked image.
As you can clearly see, the color of Saturn is off, perhaps by a program error 
or a filtering error, possibly even the atmosphere. The color of an object can 
be affected by a number of different factors and it's easily fixable.



One of the ways to get a planet's color right is to compare it to other photos 
of the same object. This photo of Saturn has an excess of red and magenta. 
Most Saturn photos are primarily brownish, and look more like this:

 

The next step is to get rid of the images shifting.
Because stacking and registering is not an exact process,
the color applied to each layer sometimes shifts and 
produces a 'haze', in this instance red on one side and blue
on the other.



The Clone tool
I find the best way to get rid of this is using the clone tool.
How the clone tool works...
What you do is identify a source point using the 'alt' key,
from which portion of the image you want to clone.
Sometimes it's used artistically, and the source point is far away
from the actual part of the image that the cloned area will go over,
but for our purpose the area will be very close to its source point.



Results of the clone tool...



The next tool that we haven't used yet is the custom filter tool,
and applying a custom matrix to the image. 
From Covington's astrophotography handbook, we will use the 
standard Photoshop 3x3 sharpening matrix which will look like this,
after going to filter>other>custom



After this, many of the steps used to finish off the previous image will 
suffice such as the dodge/burn tool and the unsharp mask.
Finally, the image will look like this:





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