Okay, now that we have some layers to play around with, the next step is to formulate an image composition and colorizing strategy. Please note that the end product objective is an asethetic, not natural observation version. A brief cavet, I'm not a Tyler Allred or a David Rankin and am not a great imager. No guarantee that this will work. Even if it does not work, it may lead to other image processing ideas. I. Color selection NASA Hubble uses a basic tri-color split complimentary color scheme - cyan-red, green and blue. http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/index.php http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/eagle.php http://www.malanenewman.com/split_complementary.html II. Historical compositions I looked through a series of Crab M1 images on APOD. Composition approaches can be broken up into three general categories, i.e. - 1. Traditional RGB 3 color mix or 2 color Ha-OIII mixes Malin, Paschoff (5 meter Hale) 1995 http://antwrp.gsfc.nasa.gov/apod/ap951122.html Jack Schmidling undated http://schmidling.com/m01.htm Hubble 2000 http://antwrp.gsfc.nasa.gov/apod/ap000605.html 2. Straight dark blue This is the quick-composition strategy that Tyler used. Nat'l Optical Observatory 1995 http://antwrp.gsfc.nasa.gov/apod/ap960626.html 3. "Cave-like" composition (bright-core dark-outer) apparently using transparent alpha layers Hubble 2009 http://antwrp.gsfc.nasa.gov/apod/ap091025.html Chandra, Hubble, Spitzer 2006 http://antwrp.gsfc.nasa.gov/apod/ap061026.html CHFT 2004 http://antwrp.gsfc.nasa.gov/apod/ap040128.html VLT 2003 http://antwrp.gsfc.nasa.gov/apod/ap030914.html Chandra Hubble 2002 http://antwrp.gsfc.nasa.gov/apod/ap020920.html III. Composition strategy for the subject image I've decided to try for a "cave-like" composition using layered coloring after the VLT 2003 image. This composition strategy will try stacking layers - principally transparent alpha layers with foreground objects - and a mask in the outlayers to create the "cave". From background to foreground, the proposed layers are: A. The interior of the cave Layer01 Black background base layer Layer02 Bright-blue from the blue image (201000115_cleanedblue_bit8) Layer03 Bright-cyan from the Ha image (20100115_cleanedHa_bit8) Layer04 A luminous structure layer for the cave's interior from the OIII image (20100115_cleanedOIII_bit8) B. Outer nebulousity rings Layers05, 6, 7 and 8 Two to four rings in green and red made from transparent alpha layers from the Ha, OIII and red layers with the core masked out to let the inner cave shine through. Layer9 A luminous structure layer from the exterior from the OIII image (20100115_cleanedOIII_bit8) D. Stellar foreground Layer10 A transparent alpha layer that contains only the stars. (201000115_cleanedstarsonlyLayerAlpha_bit8) Clear Skies - Kurt