gboulton wrote:Well, I'm totally at a loss on the LRGB thing at this point.
I really can't figure out what I need to be doing. I can split the TIF into RGB, and then desaturate for a Lum, or use the blending method you describe, Ivo...but...then what?
Sorry to be so ignorant, but I quite simply have no clue what I'm doing at this point.
No probs!
Creating a synthetic luminance basically involves throwing all data that you captured on a heap, regardless of wavelength (color).
To make sure the 'heap' has the correct measure of signal of each channel, you need to create a blend according to exposure time.
In PhotoShop or StarTools that is currently not very elegant - it requires blending multiple layers. In PixInsight you can specify a formula. (i.e. 'give me 20% Ha + 30% OIII + 50% SII').
(examples of how to do it in StarTools
here and
here)
Now, fortunately you used a DSLR. That makes the calculation (equal measures) easy. In StarTools instead of opening the image in color using the 'Open' button, you can use the 'LRGB' module and open the color file as your Luminance file. StarTools will automatically average your channels and create a synthetic luminance file from the color data. Do note that StarTools assumes no channel multiplication (aka white balance) was performed, i.e. StarTools assumes that these are raw, unadulterated photon counts.
Process this luminance frame, trying to tease out as much detail as possible. Save the file for later use.
Now for your colors; open LRGB and load the same file for R, G and B. Find out what the multipliers are for your camera (450D) for daylight and set the R, G and B ratios accordingly (if you don't know, DCRAW can tell you; use 'dcraw -i -v <filename>.CR2' on a single frame on the command-line and it'll spit out the whitebalance values for daylight).
As a side note, the file you posted on astrobin seems too red for it to be a non-whitebalance corrected file. I'm wondering what's going on here...
Once you loaded up your color file in this way, process it as normal and don't be afraid to a more heavy-handed approach to noise reduction (the human eye doesn't mind colour loss). Save the file.
Now launch LRGB once again, load the processed synthetic luminance file as your luminance layer and the color file for R, G and B. You should now have a composite that looks nice!
