Sigma image

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m (SDSS sigma image)
m (SDSS sigma image)
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There is gain + rdnoise depending on camcol (for each filter) in the table (same link)!
There is gain + rdnoise depending on camcol (for each filter) in the table (same link)!
To get sigma image go from Nmgy to DN:
To get sigma image go from Nmgy to DN:
-
\; sky-subtracted image as well as calibrated in nanomaggies/pixel
+
";" sky-subtracted image as well as calibrated in nanomaggies/pixel
img= mrdfits(framename,0,hdr)
img= mrdfits(framename,0,hdr)
nrowc= (size(img,/dim))[1]
nrowc= (size(img,/dim))[1]

Revision as of 10:25, 11 June 2018

SDSS sigma image

http://data.sdss3.org/datamodel/files/BOSS_PHOTOOBJ/frames/RERUN/RUN/CAMCOL/frame.html

There is gain + rdnoise depending on camcol (for each filter) in the table (same link)! To get sigma image go from Nmgy to DN: ";" sky-subtracted image as well as calibrated in nanomaggies/pixel img= mrdfits(framename,0,hdr) nrowc= (size(img,/dim))[1] sky= mrdfits(framename,2)

sky image the same size as the frame image, in units of counts

simg= interpolate(sky.allsky, sky.xinterp, sky.yinterp, /grid)

a calibration image the same size as the frame image, in units of
nanomaggies per count

calib= mrdfits(framename,1) cimg= calib#replicate(1.,nrowc)

Original image in DN

dn= img/cimg+simg

Corresponding sigma image

dn_err= sqrt(dn/gain+darkVariance) ; in counts

to get those errors into nanomaggies, you simply apply back the calibration

img_err= dn_err*cimg

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