You all have seen the Hubble’s breathtaking images. These images are not just simple photographs, but digital composites made of two or more greyscale images taken by different cameras onboard the space telescope. This video shows exactly how.
The time lapse shows how the image of NGC 3982 – a spiral galaxy 68 million light-years from Earth, in the Ursa Major constellation – was made using seven greyscale images from three of Hubble cameras. The processing job took 10 hours of scaling, rotating, aligning and colour processing.
This processing work doesn’t mean that the images are fake – even while at times they appear to be total fantasy. And it doesn’t mean that, if we went there in a spaceship all of Hubble’s images would be different from what we could see in person.
The Photoshop processing just transforms the raw data into a format that humans can see. Our eyes are only capable of registering a very limited part of the electromagnetic spectrum, from 390nm to 750nm, while Hubble can see the optical, ultraviolet and near-infrared spectrums, a lot more details than what we can see with our bare eyes.
Scientists have to choose how to represent this information visually so we can understand it and analyse it. Sometimes they will choose to give use a natural representation, which is very close to what we would see if we got there in the Enterprise. Other times they will choose representative colour, which helps scientists see invisible features of the object – like those that are only captured in infrared or ultraviolet. And sometimes they show the image in enhanced colour, a hyperrealist mode that brings a lot of hidden, subtle details. [HubbleSite]