Fans or blotches?
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by
Peek
I'm just trying to figure out how to draw the line between a fan and a blotch. In this image I put three as fans, and only the small one close to the center as a blotch. But then I started thinking about the distribution of dust, especially the one in the top right corner. The dust seems to be so uniformly dark, which I guess means it's evenly distributed. This makes it look like it's not a fan, where the dust has spread out in one direction, gradually thinning with distance from the source. So that would more be a blotch. Is my thinking right, or am I completely off?
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by
Kitharode
moderator
Hi Peek. Whenever it's not obvious whether you're looking at a fan or a blotch, it's up to you to draw your own conclusion as to what it is. Your thinking on the distribution of dust is sound enough. Most fans do get a bit fainter at the tail end and this can help you make a decision on what it is. The main difficulty (for me) is when they run over the edge of the image, like the one in the top right of your image.
My feeling is that in the end analysis we'll end up with a continuum of shapes. Definate fans at one end, definate blotches at the other, with all sorts of blans and fotches inbetween. 😃
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by
Peek
Kitharode, thanks for your reply. You're right, the big one in the upper right corner does go over the edge of the image, so there's no way of telling if it fades out gradually or ends abruptly.
I think you are right about the continuum of shapes, instead of two sharply contrasted and easily distinguished categories. Which I guess reflects how they are created, meaning not only in two different and distinct ways, but more in a way that can vary gradually from one end of the scale to the other.
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Kitharode
moderator
in response to Peek's comment.
We've also learnt that 'slope' is very important when it comes to the shape of fans and blotches. One discussion worth having a look at is this one: http://talk.planetfour.org/#/boards/BPF0000009/discussions/DPF0000cp7
Wassock's post and picture on page 4 is particularly good, I think.
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