Quote:
Originally Posted by PKay
Maybe Rick
Back to basics: best to eliminate problems at the source.
As to the formula I really don't understand it.
Does it assume the dust is a certain size?
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I was being a little tongue in cheek, Peter. I agree it's better to remove the dust but sometimes you can't. I use remote/unattended systems and flats deal with dust donuts just fine in between infrequent cleaning and maintenance.
I have never thought deeply about the formula but it does seem to work. If you have a bunch of dust specks at the same distance the shadows all look pretty much the same size even though the specks presumably vary in size. They are a shadow of the aperture (solid for a refractor and donuts for scopes with a central obstruction.) Something to ponder when I run out of data to process
Cheers,
Rick.