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Re: Edge and Hot pixels



On Thu, 23 Dec 1999 18:49:50 GMT, andrew.bennett@ns.sympatico.ca (Andrew Bennett) wrote:
*>I have been taking another look at edge pixels on CD5.
*>Results can be found in
*>http://www3.ns.sympatico.ca/andrew.bennett/tass/mkivedge.html

This is pretty good work, now I need to look at Tom's hardware and notes
to see how Andrew's findings work with mine on the edge columns.

*>I have extracted all the pixel values at locations
*>previously identified as "Hot" into a spreadsheet and
*>have compared the mean "Hot" pixel value with the estimate
*>of dark current obtained from median of col 2040 - col 2.
*>
*>The results are reported in
*>http://www3.ns.sympatico.ca/andrew.bennett/tass/dark.html

Any chance you could post the locations of those "hot" pixels on
your Web site? If you export the spreadsheet columns to text
then any of us could import them. An X, Y and max pixel value
would be sufficient. I want to look at these hot sites myself.
In any case, for these six dark images we could all talk about
the same items if we use a common reference.

*>3) The "Hot" pixels are consistent. I hypothesize that the
*>intermittent ones seen on the dark images when creating the
*>index are mostly the result of an odd=20
*>phenomenon I read about in a book on CCD's. Yes - I do
*>sometimes read books. This is the phenomenon of hot pixels
*>turning on rather abruptly as the temperature is raised. And
*>conversely, turning off rather abruptly as the temperature is
*>lowered.

(OK, OK. There are a number of ways pixels can get hot. Sorry I
got smart about it previously, guess I had a fever.) Some hot pixels
are intermittant, some are causal, some are persistant. That's
why I want to look at these more closely myself. I'll reread
these reports after the holidays and see what sense I can make
of all these, er, pixel events. I'll add the results to my dark
report on my Web site. I'll make it a Tech Note when it gets
stable enough.

(I also asked Andrew privately for some clarifications on his
report on saturated sources, which is where he processes two
images with the bright/saturated sources "stripped" out. It's
informative and gives some clues as to what "star" has to
deal with on the CD #5 images. I'll comment more publically
after some feedback from Andrew, and after some more work on
my part on coma. And of course the holidays.)

Season's regards to all,
Herb Johnson

Herbert R. Johnson              http://pluto.njcc.com/~hjohnson
hjohnson@pluto.njcc.com         voice 609-771-1503, New Jersey USA
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