Sigma image
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m (Created page with '== 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 th…') |
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http://data.sdss3.org/datamodel/files/BOSS_PHOTOOBJ/frames/RERUN/RUN/CAMCOL/frame.html | http://data.sdss3.org/datamodel/files/BOSS_PHOTOOBJ/frames/RERUN/RUN/CAMCOL/frame.html | ||
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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: | ||
Revision as of 10:24, 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
