CCD data reduction
Contents
Creation of lists
filter="L"
ls bias*[0-9].fit > bias.list
ls dark600s-00*fit > dark600s.list
ls dark*5sec*fit > dark5s.list
ls flat*${filter}.fit > flat${filter}.list
sed s/^/b/g flat${filter}.list > bflat${filter}.list
sed s/^/bd/g flat${filter}.list > bdflat${filter}.list
ls ngc*${filter}.fit > ${filter}.list
sed s/^/b/g ${filter}.list > b${filter}.list
sed s/^/bd/g ${filter}.list > bd${filter}.list
sed s/^/bdf/g ${filter}.list > bdf${filter}.list
sed s/^/objbdf/g ${filter}.list | sed s/fit/pl/g > objbdf${filter}.list
Basic data reduction
- Below is a bash script that creates lists of all images: biases, flats, darks and targets.
- Special case of dark frames of 600sec that Milankovic generates is used
- Last lines create ascii files with median values in flat frames that will be used
- for their normalization
- !/bin/bash
rm *list for frame in $(ls *fit); do filterType=$(gethead filter $frame) imageType=$(gethead imagetyp $frame) outFileName=$(echo $imageType | tr '[:upper:]' '[:lower:]') # test if DARK if [ ${imageType} = "DARK" ]; then exptime=$(gethead exptime $frame | cut -d. -f1) ls $frame >> ${outFileName}${exptime}"s".list echo "b"$frame >> "b"${outFileName}${exptime}"s".list else ls $frame >> ${outFileName}${filterType}.list fi # test if LIGHT and create additional lists if [ ${imageType} = "LIGHT" ]; then exptime=$(gethead exptime $frame | cut -d. -f1) echo $exptime >> exptime${filterType}.list echo "b"$frame >> "b"${outFileName}${filterType}.list echo "bd"$frame >> "bd"${outFileName}${filterType}.list echo "bdf"$frame >> "bdf"${outFileName}${filterType}.list else if [ ${imageType} = "FLAT" ]; then
echo "b"$frame >> "b"${outFileName}${filterType}.list
echo "bd"$frame >> "bd"${outFileName}${filterType}.list
echo "nbd"$frame >> "nbd"${outFileName}${filterType}.list fi fi done
- Create dark current corresponding to each light frame using exposure time
for exptime in $(ls exptime*.list); do filter=$(echo $exptime | sed -e s/exptime//g -e s/\.list//g); awk -v filter=${filter} '{print "dc"NR"_"filter".fits"}' exptime${filter}.list > dc${filter}.list done
if [ -e reduce.cl ]; then rm reduce.cl; fi echo "imdelete master_bias,dc_600s,dc_5s,dc_1s" >> reduce.cl echo "imcombine @bias.list master_bias comb=med" >> reduce.cl echo "imarith @dark600s.list - master_bias @bdark600s.list" >> reduce.cl echo "imarith @dark5s.list - master_bias @bdark5s.list" >> reduce.cl echo "imcombine @bdark5s.list dc_5s comb=med" >> reduce.cl echo "imcombine @bdark600s.list dc_600s comb=med" >> reduce.cl echo "imarith dc_600s / 600 dc_1s" >> reduce.cl
for flats in $(ls flat*list); do filterType=$(echo $flats | sed s/flat//g | cut -d. -f1) #echo $filterType echo "imarith @flat${filterType}.list - master_bias @bflat${filterType}.list" >> reduce.cl echo "imarith @bflat${filterType}.list - dc_5s @bdflat${filterType}.list" >> reduce.cl echo "imstat @bdflat${filterType}.list fields=\"image,midpt\" format- > norm${filterType}.txt" >> reduce.cl done
BPM & object mask creation
# cat bpmask.cl
imstat dc_300s field="image,mean,stddev" for- > hot.txt
imstat master_flat_FILTER fields="image,mean" for- > cold.txt
cl < bpmask.cl
# awk -v filter="L" '{print "imexpr \"((a > b) ? 1 : 0)\" hot"filter".pl a="$1" b="($2+3.*$3)*0.75}' hot.txt > hot.cl
# awk -v filter="L" '{print "imexpr \"((a < b) ? 1 : 0)\" cold"filter".pl a="$1" b="$2*0.9}' cold.txt > cold.cl
cl < hot.cl
cl < cold.cl
# cat bpm.cl
imexpr "max(a,b)" bpmFILTER.pl a=hotFILTER.pl b=coldFILTER.pl
hedit @bdfFILTER.list BPM bpmFILTER.pl add+ ver-
# sed 's/FILTER/'${filter}'/g' bpm.cl > dobpm.cl
cl < dobpm.cl
# Object masks creation
nproto
objmask @bdfFILTER.list @objbdfFILTER.list masks="!BPM" hsig=2 lsig=2
Astrometry
# cat astrometry.sh
gethead OBJCTRA @bdfFILTER.list > name_ra.txt
gethead OBJCTDEC @bdfFILTER.list | awk '{print $2,$3,$4}' > dec.txt
paste -d" " name_ra.txt dec.txt | awk '{print $1,($2+$3/60+$4/3600)*15,$5+$6/60+$7/3600}' > astrometryFILTER.txt
# sed s/FILTER/${filter}/g astrometry.sh > astrometry${filter}.sh
sh astrometry${filter}.sh
# This could be used:
# cat komanda.sh
solve-field img --ra imagera --dec imagedec --radius 0.2 --scale-units arcsecperpix --scale-low 0.38 --scale-high 0.40 --crpix-center --wcs img.wcs
### The next command creates new files instead of just wcs binaries that can later be added to the header. It's a stand-alone command. And should be ignored.
### solve-field img --ra imagera --dec imagedec --radius 0.2 --scale-units arcsecperpix --scale-low 0.38 --scale-high 0.40 --crpix-center -p -N wcsimg.fit \
### -O -I noneI.fits -M none.fits -R none.fits -B none.fits -P none -k none -U none -y -S none --axy noneaxy
#while read line; do img=$(echo $line | awk '{print $1}'); imagera=$(echo $line | awk '{print $2}'); imagedec=$(echo $line | awk '{print $3}'); sed -e 's/img/'$img'/g' \
-e 's/imagera/'${imagera}'/g' -e 's/imagedec/'${imagedec}'/g' komanda.sh; done < astrometry${filter}.txt > doAstrometry.sh
# Or this:
awk '{print "solve-field "$1" --ra "$2" --dec "$3" --radius 0.2 --scale-units arcsecperpix --scale-low 0.38 --scale-high 0.40 --crpix-center -p -N wcs"$1" \
-O -I noneI.fits -M none.fits -R none.fits -B none.fits -P none -k none -U none -y -S none --axy noneaxy --wcs bla.wcs"}' astrometry${filter}.txt > doAstrometry.sh
# /bin/bash doAstrometry.sh
#ls *wcs > wcs${filter}.list
# echo "wcscopy @bdf${filter}.list @wcs${filter}.list ver-" > dowcs.cl
cl < dowcs.cl
Supersky flat
# Creation of super sky flat, normalization to each individual image median background and final stacking
# cat stat.cl
real mini
real sky
imstat("img",fields="min",lower=INDEF,upper=INDEF,for-) | scanf("%g", mini)
imcalc(input="img,msk",output="skyimage",equals="if(im2==0.) then im1 else "//mini-0.001,ver-)
imstat("skyimage",fields="midpt",lower=mini-0.001,upper=INDEF,for-) | scanf("%g", sky)
print("img"," ",sky)
imarith("img","/",sky,"norm")
imdelete("skyimage",yes)
# while read line; do img=$(echo $line | awk '{print $1}'); msk="obj"${img%.*}.pl; rsky="norm"${img}; cat stat.cl | sed -e 's/img/'${img}'/g' \
-e 's/msk/'${msk}'/g' -e 's/norm/'${rsky}'/g'; done < bdf${filter}.list > bla.cl
cl < bla.cl > med_values.txt
# ls normbdf*fit > norm.list
imcomb @norm.list norm.fits comb=med masktype="!OBJMASK" maskval=0
# awk '{print "imarith norm.fits * "$2," n"$1}' med_values.txt > donorm.cl
cl < donorm.cl
# awk '{print "imarith",$1,"-","n"$1,"s"$1}' med_values.txt > do.cl
cl < do.cl
imcomb s@bdfFILTER.list final.fits comb=med offset="wcs"
Surface brightness limit
1. Calibrate the image taking non-saturated stars and not too faint stars: intercept and slope (TOPCAT with SDSS DR12 from Vizier) 2. Calculate statistics inside at least 20 (empty, i.e. without objects) boxes of the size of 10" (for example if 1pix=0.396" than 10"~25 pix so boxes = 25 pix × 25 pix) 3. Take the mean value of the standard deviation inside boxes and it's standard deviation 4. Calculate SBmin and SBmax as: SBmax =-2.5*log10(<σ>-stdev(<σ>))*slope+intercept SBmin =-2.5*log10(<σ>+stdev(<σ>))*slope+intercept where <σ> is the average standard deviation inside boxes and stdev(<σ>) its standard deviation. 5. Finally, 1 sigma surface brightness limit (SBlim) is given as: SBlim = (SBmin+SBmax)/2 +/- (SBmax-SBmin)/2
