[Image of Sun]

Image Processing


When taking images of the sun we were not able to get a field of view wide enough for the entire solar disk so took multiple images. In order to put the Registaxed images together a free program called imerge was used.

Once the images have been aligned together to form a whole picture of the sun the program SAO Image DS9 or Paint shop pro can be used. This allows us to add colour and bring out extra detail in our black and white images. DS9 is the simplest way to add colour, by opening up the image and selecting colour BB and holding down the right mouse button and moving the curser. A reasonably bright sun colour can be achieved

Paint shop pro allows you to enhance the photos far more. While earlier images required a larger change in the use of wavelets compared to later images. Paint shop was also required more during the early images to try and bring out details. Much of this is probably not needed for the newer settings.

Darkening background

The images background could some times be coloured due to noise created in trying to bring out detail. This could be changed by resetting the black point. By selecting adjust and going to colour balance and selecting black and white points. A table like the one shown below should emerge.

[black and white]

By taking a sample of your background this will become the standard or cut off point for black. so will darken your image

Enhancing detail

In order to enhance detail in the image, the sharpening tool can be used. This will strengthen dark features such as sun-spots and filaments. By going to the left hand side bar and selecting the freehand tool shown below.

[Free hand]

Then using this to high light an area containing a filament or sun-spot and selecting adjust and scrolling down to sharpness and selecting sharpen or sharpen more. You can bring out the detail and enhance the image greatly.


It was found when taking earlier images that to get a final image with both sun spots and prominences. A layering technique was needed as prominences were only visible when over exposed. This involved producing an image with high gamma and producing a more normal image and layering on to each other. With the high gamma image showing well defined prominences and the normal image showing detail on the surface. Firstly both images need to be opened in paint shop. Then by copying the normal image and right clicking on the gamma image and scrolling down to paste and paste as new layer or (Ctrl+L) the image will be layered on top of each other. In the bottom right hand corner their is a layer section, as shown below. [layer]

By right clicking on Raster 1 and going to properties and then blend ranges. You can vary the Blend range as shown below to bring the prominences out

[blend ranges]

By then selecting layers at the top and scrolling down to merge and selecting merge visible. You will be left with one complete image.


Lastly in order to get colour on the images their are a number of ways. By going to adjust and selecting colour balance you will be presented with a range of ways to edit the colour of the image. Using either RGB or colour balance is most simple. They both involve increasing red, decreasing blue and slightly decreasing green but depend on the brightness of the image.