We have two images for you today. Both were processed, by one of our members Dean – you’ve seen his work here before. The image is of two objects, one embedded within the other. The coloured clouds of dust and gas is IC410 a diffuse nebula being illuminated (ionised) by hot bright young stars and NGC1893, known as an open star cluster – basically a close grouping of stars at the centre of the image.
The first was colour calibrated using actual stars as a white reference and applying that to the whole image. Much in the same way your colour camera or phone decides how render natural looking colours in the pictures you take with these devices.
Looking at the first image, we see almost exclusively an Orange/Red. This colour is associated with ionised Hydrogen (Hα), the most abundant of the gases in space.
Now let’s looks at the second image. The stars themselves have been calibrated in the same way, but the rest of the image – all those clouds of gas and dust, were calibrated using the nebula itself as a white reference.
What we end up with is an image that is displaying the ionised Hydrogen as before, but now we also get correct rendering of the abundant (Teal coloured) ionised Oxygen (OIII), thus creating an image that is much more interesting as well as significantly more informative on what gases make up this object.