Quote:
Originally Posted by Shiraz
just trying to show what circumstances are necessary before the technique can work well. If your optics produce vignetting over the chip scale, flats are essential, regardless of actual chip size.
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And that's about it Ray...being able to do without flats is simply a function of ones system ie a fully illuminated field, a chip with low NU, clean correctly sized filters, wide image train openings to avoid vignetting, a dark sky and..
voila 
I am able to surface extremely faint features without flats and I have not seen a single dust donnut, not one, even with extreme stretching
Mike