[Aavso-photometry] Re: Cosmic Rays

[Justin Pryzby]

I examined some images taken previously with our 765x510 ST7E at -25C
degrees at an altitude of between 20 and 45 degrees, and found, on 29
darks of 2 minutes each, 19 definite cosmic rays [0], which have
values between 10s and 100s above the background, with perhaps a
typical peak-pixel value of 50.

In the process, I implemented "highest absolute deviant" combination
[1].  There is [presently] no "normalization" as Michael mentioned, so
this probably wont work well at all for data images.  I built a
windows executable [2] also for your amusement.

-- 
Clear skies,
Justin

References

[0] http://justinpryzby.com/astro/cosmics2.png
    This is the result of Wolfgang's algorithm, which attempts to show
    all the cosmics on all the input images.  The fits image in
    question has the following statistics:

    mean    stddev  min     max
    9.29017 3.59488 2.55172 1351.28

    The max is at (135, 306), which is not a [consistently] hot pixel.
    Note that the minimum is positive, even though the input values
    were occasionally negative (remember, the inputs are: bias_i -
    (1/N)*sum(bias_i).  So it seems that, for sufficiently large N,
    this, in fact, reduces to the "max" operator.

[1] https://fiddlernet.net/svn/libastro/trunk/mostdev.c
    You'll notice that this project is a work in progress.

[2] http://justinpryzby.com/astro/code/mostdev.zip