The image of the Crab nebula I finished on the 3rd did not seem right, I decided to re process the narrowband data – Ha, OIII and SII. As Deepsky Stacker ( DSS ) sends a 32bit unprocessed image to the folder that contained the light frame images in the first place it was fairly simple, I just opened that ” untitled ” image in Photoshop CS5. The program can work on 32bit images – but not all of the resources can be used, instead you have to convert the image to 16bit to unlock all the editing options, again simple just go to image, type select 16bit from the dropdown menu and it will open up HDR Toning, this stretches the image so you go from a black seemingly devoid of detail image to one that shows everything. you then reduce the highlights and the shadows ( both on handy sliders ) until all the whites are not overexposed and the shadows are not totally black. This is a lot easier than trying to preprocess the image in DSS, I did this to the three images then copied and pasted them into their respective colour channels in a new image of the same type and size, Ha into Green, OIII into Blue and SII into Red.
This creates a colour image from three monochrome images, Then using the selective colour adjustment option you adjust the Greens, Yellows and Cyans with the figures in the following image.
This gives what is called the Hubble palette or colour mapped image, coupled with some noise reduction and a bit of subtle sharpening to finish things off – I ended up with a cleaner image than last time. I’m happier with this image.