Cosmic rays
The new code rejects cosmic rays- it will also reject
transient objects. Here are a couple of Linhua's cosmic rays.
run 4145 field 65
Run 4145, field 65 at ra,dec= 353.30172,-0.783305 and
coadd image 100005-2-357, all z-band.
The cosmic ray:
A star:
The old coadd:
The new coadd:
run 4145 field 66
Run 4145, field 66 at ra,dec= 353.42806,-0.731476
and coadd image 100005-2-357, all z-band.
The cosmic ray (something that got poorly interpolated over):
The old coadd:
The new coadd:
coadd run 100005/100006 field 375
Run 1, field 375 at ra,dec= 356.09181,-0.809464
z-band.
Cosmic ray 1
Cosmic ray 2
The old coadd:
The new coadd:
200006 rerun 0 Coadd
The new code involves a wholesale
rewritting of the old. So, here is an image
made using the same weighted mean algorithm
that we have been using, with the old coadded
image subtracted. This is fpC-200006-r1-0244.fit.
The delta image has a mean of
a mean of -0.000378 and a sum of -1153
In a 60x60 box about the "star" below the "0 deg" button
there is a sum total of -0.18 counts, and a mean of -0.0000049.
The black and white structure has an amplitude of about 10^-7.
All of this must be roundoff error.
The new "sigma clipping" algorithm,
actually a inter-quartile range rejection routine,
produces an identical image to the new weighted
mean image- there was no clipping done.
The new image looks like:
and that star below the "0 deg" button has a peak of 8500 DN.
If one takes the ignore threshold down to 10, then one finds
a few pixels that are clipped around a saturated star:
Last month's plots and web page are at:
coaddApr07.html and
coaddNov06.html and
coaddOct06.html.