On 28 Nov 98, at 12:44, Garth Wood wrote:
> At 12:08 PM 11/28/98 -0800, John Petrush wrote:
> >"wonky"?? Is that a technical term <g>.
>
> In my vocabulary, yes. ;-)
>
> >...with an
> >astro CCD one takes two exposures to get a picture - a "dark frame" and the
> >image itself. The dark frame is all black, except for the noise patterns
> >for that CCD. The dark frame values are then subtracted from the image
> >values to produce the first generation image.
>
> Interesting. From what you mentioned above, John, I'm assuming that the
> noise characteristics of the specific CCD field are always the same? Sure
> makes it easy to manipulate, if that's the case. I also assume that
> Sebastien would have to make "dark field" exposures that are always the same
elapsed time as the actual subject exposure, in order to do this subtraction
properly...
>
> Garth
>
And from what I understand, fluid cooling the CCD reduces the noise level
even further. A friend's father has a custom built telescope shed (the roof
rolls off - pretty cool), and he showed me the liquid cooling system for the
CCD that he uses. The results from this are pretty impressive.
Shawn & Janis Wright
swright@xxxxxxxxx
http://Zuiko.sls.bc.ca/~swright
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