Ha for Luminance Substitution Technique
Jack Harvey SSRO/PROMPT
01/14/08
I have developed a new technique for combining Ha to a RGB image. This technique was perfected using PixInsight, however other programs that allow you to break down a RGB image into the R,G,B frames as well as extract the Luminance will allow this to work. Once the luminance is extracted from the RGB and the RGB is broken down into R,G, & B a new combine of Ha,R,G,& B is made and the image given final adjustments with histogram, curves etc. The technique is described stepwise below:
1. Process the Mean Ha frame with decon, wavelets or what ever you deem to get a good Ha image. Then mask the image and use ACDNR or a noise tool to smooth the periphery of the Ha nebula, somewhat aggressively. Adjust mid point with Histogram (see step 2).
2. Extract the Luminance from a processed RGB of the image using the extract channels, with L checked and a and b unchecked on the CIE button. Save this extracted Lum frame as we will re insert it with Pixel Math near the end of the processing. I did look at the Lum to adjust the histogram for the above Ha to be close to that of the Lum frame.
3. Now extract the R,G, and B frames form the RGB using the Extract Channels but this time the RGB button.
4. In LRGB Combination tool put the Ha frame in the Lum slot and the RGBs in the correct slot. Add a slight amount of saturation (lower the sat slider 15-20%) and start with about 50% of Luminance contribution using the slider in the upper right. You can run several diffferent percentages of the "Lum" which is really Ha and see how much is best by comparing the output images.
5. Now recombine the HaRGB with the previously extracted Lum frame using a 50%-80% of the Lum with Pixel Math.
6. Make final adjustments with histogram, etc.
Example:
HaR_RGB Image of NGC 346
New HaRGB Technique
Original Reference and other examples:
http://pixinsight.com/forum/viewtopic.php?p=2445#2445
