Help:Tutor process

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Processing the stacked image

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Now that the stacked image has been generated, you may select some "Process" tools, to enhance the final result. An easy combination is to use the deconvolution Deconvolution.gif and the unsharp mask UnsharpMask.gif ; alternatively, you can use the "Wavelet" filter Wavelet.gif, if you are familiar with it.

Deconvolution.gif Deconvolution

En-deconvolution.jpg

The deconvolution filter "unblurs" your image. You must select the "blurring-radius" in your image, usually 2 to 3 pixels, and then adjust the threshold to obtain acceptable results (1 means no deconvolution, 0 means too much ;o).

UnsharpMask.gif Unsharp mask

En-unsharpmask.jpg

The unsharp mask filter increases the contrast of the small details and levels the slow brightness changes (soft planet edges for example). Experiment with the sliders for best results...

To come back to the settings of the deconvolution filter, select the "Processings" toolbar icon (or the "Process stack" menu), and change any setting of the image processings applied so far.

En-procstack.jpg

Chromaticalign.gif Chromatic align

If your image is affected by some chromatic dispersion (one edge is slightly red and the opposite, slightly blue), use the "Chromatic align" tool to correct for it.

En-chromalign.jpg

Chromaticlevels.gif Levels and gamma adjust

Finally, adjust the brightness and contrast of your image by using the black and white level, and the gamma correction sliders at the bottom right of the image frame.

En-adjust.jpg

If you want more control over the levels for each color in your image, use the "Levels and gamma" tool :

En-chromalevels.jpg


Do not push the process too far. Keep in mind the words of Matt BenDaniel (Sky & Telescope, April 2002) :

«Whenever you do something, if image processing artifacts begin to be detectable, you've gone too far. Subtlety is the key. Successful processing does not look processed at all

The processed image is displayed in the image frame at the right. When you are satisfied with the result, save your work with the "File→Save" menu item, in case you later want the improve on the image ;o). If you are really satisfied with the processed image save it in an image file using the "File→Save image..." menu item ; choose the TIFF format.

To flip, rotate, or otherwise adjust your images you may use an all purpose image tool such as the Gimp (it would be THE choice, if only it supported 16 bits samples). This may help you put your images right side up (depending on what you call "up" ;o), tweak the levels and colors, here is the result.

Jupiter.jpg

This image was acquired on March 14, 2005 with my home-made 200 mm newtonian telescope, a ToUcam webcam connected with a "do it yourself" eyepiece projection system yielding a 3.1 m focal length. It was later processed with Lynkeos as a test case.

Frequently Asked Questions...