Quote:
Originally Posted by Placidus
Suppose God took a photo of some clouds and patchy mist, and some stars between and through the stars. In said image, we should expect that the stars are razor sharp, and if there are two stars very close together on the sky, up to the seeing of say 1.5 or 2 seconds of arc, we should hope to see them as two separate objects. However, the clouds and patchy mist should not have sharp edges. They should look cloudy and misty.
If a supernova then went off to one side of the cloudy mist, that should generate sharp bubble-like shock fronts, and a perfect image would show sharp edges at the shock fronts, but not elsewhere.
I get very puzzled by what folk mean by "it looks a bit soft". Do they mean it is out of focus? Clearly that is not the case here. Do they mean that there is a grey fog across the image? That is certainly not the case here, but if one were photographing actual grey fog, one would expect to see it in the resultant image. Do they mean that there are no sharp edges? In an astronomical image, if the stars are pin-point, that would just mean that there were no shock fronts here. That is not a defect. It is not something to fix.
|
Spot on Mike.
There are always parts of nebulae that are soft and diffuse when other shock fronts or features are a lot sharper. This can be seen very clearlyin eta carina and Orion M42 periphery. If you process the field as a whole without the use of localised sharpening you can see this very obviously.