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ART ASTRONOMY Uranus
2023 on Sun, Moon, Venus & Miscellaneous PROCESSING
TUTES |
ASI224MC IMAGE PROCESSING TUTE |
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Part 3 ASTRA IMAGE 3.0 PROCESSING |
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Using Astra Image is just one processing option – we have frequently not used this and relied upon 2 or even 3 different value applications of unsharp mask in CS4 – there is often very minimal difference either way. |
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Here the image is loaded into AstraImage - note that unless you open this software full-screen on your pc the size of the representation compared to its actual size will be displayed at the bottom of the image as show here. Here the image is loaded into AstraImage - note that unless you open this software full-screen on your pc the size of the representation compared to its actual size will be displayed at the bottom of the image as show here. |
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Here I've selected "Lucy-Richardson deconvolution - this is probably the "best' type of deconvolution to use for planetary image detail enhancement, but you have to be fairly restrained in the amount you apply: please not that this is a rather old version of AstraImage & I believe that newer version have a different application rate which entails using many more "iterations" to produce the same effects. |
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There is a preview window & tab which displays the effects of various values you choose from the left-hand side: by altering these values & hitting the "Preview" tab again it displays the effects of these new values...clicking on the image in this preview window reverts the image back to a pre-deconvoluted state & is also a means of moving the image around (by clicking & dragging here) so that you can preview different areas of the planet's disk - which is advisable. There is also a point-image that shows the effects of applying various PSF's (point spread functions) which obviously vary with the curve width employed. |
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The simplest &
most practical way to show what varying the PSF/curve width does to the image
is to have this animated gif reveal various amount of application values:
this is a mono image which I will replace with a colour-planet one later but
the principles are the same - you are looking to find the values that give
the sharpest details without introducing too much noise. A good approach is
to look at one small detail in your image that displays some finer details -
the 2nd of the 2 images above has a circle around the area I concentrated
upon to determine the L-R decon values I thought
best here - look at the animated sequence of varying curve widths to see if
you can discern the values that provide the sharpest image of this small
section of detail! :) I decided that "1.6" was the optimum value for the c/width - it can be worth applying a more aggressive number (ie, higher) of iterations so that you can see the various results more clearly...but remember that you do not want to introduce to much noise into the image & also remember to move the image around in the preview window so that you can see what the effects of your choices are along the edges of the planet - you want to avoid strong edge-effects aka Gibbs Effect/sharpening artefacts. |
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Here is the result of applying 5 L-R deconvolution iterations at a curve-width of "1.6" - remembering that newer versions of this software might mean different numbers of iterations! Compare it to the image when it was first loaded into AstraImage further up this page. |
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In the 3 images above we have reduced the size of the planet to 67% or about 2/3 making this image still 200% of the original. (remembering that it was 3x the original capture scale from the drizzling in AS!3) This size reduction & more deconvolution at a smaller PSF/curve width can be beneficial, but you have to be careful about doing this 2nd deconvolution - remembering the over-sharpening warning I gave earlier! |
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The 2 images above display the 2nd lot of deconvolution & the results.. |
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Then it is saving the tif file in AstraImage & you are ready for the final post-processing stage in Photoshop. (CS4 in my examples...) |
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