Image Processing

We used two methods of image processing to maximise the information from our observations...

The "Cheap 'n Dirty" method

Using Paintshop Pro V5 and applying it's standard algorithms
Note: these images are displayed 256 (8 bit) colour GIF files at x2 size for ease of viewing on the web. Image capture and transformations in Paintshop Pro were carried out in 24 bit colour.

Raw frame as captured from the video camera.  Applying the Paintshop Pro "soften" transformation to remove interlacing scan line effects Contrast stretching transformation by increasing Shadows to 30%

 

The "Hi-Tech" method - Maximum Entropy Deconvolution

This technique uses information from multiple frames on the captured video to reduce background noise on the image and then sharpen the image.

First we selected the four best frames from the raw video, these are all less than a second apart

Frame Ref: 8 11 19 21

Next these images were aligned and superimposed into a single image using a PC based Maths package which manipulates the images as arrays of 8-bit colour information. This produces the base image in the following table. Note the reduction in background noise compared with a raw frame

 
Superimposed Base image Base image background noise x4 Raw image background noise x4
 

Finally a de-convolution algorithm was applied to the base image using a using a 5 pixel square sharpen point spread function. Then we used the techniques described above to soften and contrast stretch the image. Using a soften function after de-convolution seems counter-intuitive but it does result in a more pleasing image! 

De-convoluted image Paintshop Pro soften ... and contrast stretch

Astrostack - Freeware

Since writing the above page where the raw images were processed using the software and algorithm which Phil developed we have now processed the same frames through the Astrostack software which produced a very similar result - highly recommended for anybody starting out to use these techniques.

Comparing the final images...   

Note the following in the processed image:-

bulletThe Progress (far left) solar panels are visible
bulletThe Sofora boom is much sharper
bulletThe main Kvant solar panels are sharper
From a single frame... Using the four frames & deconvolution with Phil's code... The same 4 frames processed through Astrostack

Related links

bulletTheory paper which Phil used when programming the algorithm
bulletAnother theory site with some examples
bulletAstrostack - FREE image processing software
bulletAstroart software - some excellent before/after examples - anybody tried this software??
bulletCCDSOFT - implements Max Entropy Method & DDP techniques
bulletDr K. Okano - excellent home page from Tokyo, DDP algorithm & photo gallery

Images and content  2001 Philip Masding & Mike Tyrrell


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Page content 2001-2007 Mike Tyrrell