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&size(28){''NIC Data Reduction Manual''};
* Abstract [#o32f6cd3]
- Here we present the reduction procedures of imaging dat...
- The data are assumed to be obtained with the procedures...
- This document is based on the article below:
-- [[Ishiguro et al. 2011>http://www.nhao.jp/research/ann...
- In modifying and editing the article, some materials pr...
- You can use a set of the pipeline scripts working on th...
* The scheme of the data reduction [#cb6fd1da]
- The data reduction is outlined as follows. The names of...
+ Dark subtraction (''*.da.fits'')
+ Flatfielding (''*.fl.fits'')
+ Mask and interpolate the bad pixels
+ Mask and interpolate the hot pixels and dark pixels (''...
+ Generate the sky frame (''*.sk.fits'')
+ Subtract the sky frame (''*.ss.fits'')
+ Subtract the 'stripe' pattern of the detector (''*.sp.f...
+ Match the positions by shifting the individual frames
+ Coadd the frames to generate the combined image (''*.cm...
+ Register and assign the WCS to the combined frame (''*....
#ref(./ImageReduction_NIC.png,70%);
- The figure above shows the example image generated in e...
* 1. Dark subtraction [#l48d5654]
- Use the dark frames obtained by the procedure shown [[...
- Be sure to set the exposure time for the dark frames ex...
- Obtain 10-15 frames, and coadd them to generate the dar...
- The pipeline scripts installed in 'gamera' performs 3-s...
- If the cold shutter is not set to the appropriate posit...
- Subtract the coadded dark frame from the object frames ...
- The pipeline script generates the intermediate file nam...
After dark-subtraction j(date)_(frameID).(ObjectName)....
* 2. Flatfielding [#te07b759]
- This step corrects for the spatial inhomogeneity of the...
- Usually we recommend to use the twilight flat. [[This l...
- If you use the master flat frames provided by the obser...
- We do not have any specially-made software tools to gen...
- How to generate a flat frame is outlines as follows:
++ Obtain 5-10 (or more) pairs of flat frames with high- ...
++ Subtract the low-count frame from the high-count frame...
++ Homogenise the count levels by scale the individual fr...
++ Normalise the coadded frame so as to set the average c...
- Divide the dark-subtracted frame with the normalised fl...
- The pipeline script generates the intermediate file nam...
After flatfielding j(date)_(frameID).(ObjectName).fl.f...
* 3 & 4. Mask and interpolate the bad pixels and the hot/...
- Bad pixels (appear at fixed positions) can be removed b...
- The table shown below are the lists of bad pixels for J...
++ Mask the region with x1<x<x2, y1<y<y2, and interpolate...
++ If there are only two columns, mask only the single pi...
-- J band
277 291 134 148
186 191 229 236
260 270 1017 1023
-- H band
277 291 134 148
186 191 229 236
961 962 672 673
1002 1004 652 654
1005 1006 649 651
966 967 612 619
964 966 609 614
1001 1007 646 654
13 15 242 245
-- K band
140 141 549 551
162 163 806 807
162 805
163 804
164 167 801 803
162 170 795 800
171 173 798 802
186 191 229 236
277 291 134 148
320 321 586 589
321 323 591 593
778 779 682 688
780 786 671 676
779 780 677 680
785 789 670 671
- Hot/dark pixels can be removed using, e.g., IRAF/noao.i...
cosmicrays @obj_fl.lst @obj_cr1.lst
imarith @obj_cr1.lst * -1 @obj_cr2.lst
cosmicrays @obj_cr2.lst @obj_cr3.lst
imarith @obj_cr3 * -1 @obj_cr4.lst
obj_fl.lst: list of the flatfielded files
obj_cr?.lst: list of files to be generated
-- The recommended parameters for IRAF/cosmicrays are: th...
-- You can use other tools such as L.A.Cosmic
- The pipeline script generates the files named ''*.rr.fi...
After removing Bad/Hot/Dark pixel j(date)_(frameID).(...
* 5 & 6. Sky subtraction [#g19ae996]
- The 'sky' here means 'winding' pattern that cannot be c...
- Step 5. The sky frames are generated by median-stacking...
-- If the stars are not so crowded, you can use the raw o...
-- If there are many stars within the FoV, you need to ob...
-- The sky frame can be used even when containing several...
-- The procedures are outlined below. (This is not the on...
+++ Normalise each sky frame to the median pixel value.
+++ Median-stack the normalised frames. (e.g., using IRAF...
+++ Estimate the sky level of each object frame, and scal...
- Step 6. The sky subtraction is done by simply subtracti...
- The pipeline scripts generate the following two kinds o...
Sky frame generated j(ObjectName).sk.fits [e.g., jSN...
Sky-subtracted image j(date)_(frameID).(ObjectName).ss....
* 7. 'Stripe'-pattern subtraction [#ra32f91c]
- The NIC imaging data have 'stripe' pattern coming from ...
-- This pattern is thought to be due to the voltage fluct...
-- The amplitude of this pattern is almost constant for e...
-- There are two ways of subtraction as follows.
++ For sparse fields, i.e., fields containing few stars (...
--- Extract 20-100 lines without any stars, and average a...
--- Do the same procedure for both the upper- and lower h...
--- Subtract the 'stripe' pattern profile of the upper ha...
#ref(./NIC_colpattern.png);
--- In the example above the regions outlined with the gr...
++ For crowded fields, i.e., fields containing many stars...
--- The example below has many stars in the FoV, and 'lin...
--- Calculate the median count for each column for each o...
--- Subtract the profile from the object frames, similarl...
#ref(./NIC_colpattern_median.jpg,70%);
--- The example above shows the result of subtraction wit...
- The pipeline scripts generate the files named ''*.sp.fi...
After subtracting the 'stripe' pattern j(date)_(frameI...
- The pipeline scripts also try to register the WCS at th...
* 8 & 9. Position matching & stacking [#a730298d]
- Measure the positions of astrometric reference stars . ...
- Shift the images so that the reference stars are locate...
-- You do not need to take account of distortion, as the ...
-- The position angle is usually set to be constant, so t...
-- You can utilise the whole FoV of NIC by creating large...
- Stack the object frames after matching the positions (e...
- The pipeline scripts generates the files shown below, n...
After matching j(date)_(frameID).(ObjectName).sf.fits ...
After Stacking j(ObjectName).cm.fits [e.g., jSN2012dn...
* 10. Astrometry [#rc012d31]
- Obtain the coordinate system using the stars within the...
-- ccmap : Reads the list of object coordinates and corre...
-- ccsetwcs : Inputs the 'image to be registered the WCS'...
- This is not the only way to do this. You can also use [...
- See also: [[WCSTools>http://tdc-www.harvard.edu/wcstool...
- The pipeline script uses 'imwcs' of WCSTools, and regis...
gamera% ds9 &
gamera% getwcs.sh [file name].cm.fits
-- Note that the script does not run on machines other th...
- The script generates the following files named ''*.spw....
After 'stripe' subtraction + WCS j(date)_(frameID).(...
After stacking + WCS j(ObjectName).cmw.fits [e.g., j...
-- The astrometry process includes the calculation of the...
* Revision history [#pf25dc55]
- 2019.09.10 Created based on the Japanese version (T. Sa...
- 2019.09.12 Fully revised and opened for public (T. Saito)
終了行:
[[staff]]
&size(28){''NIC Data Reduction Manual''};
* Abstract [#o32f6cd3]
- Here we present the reduction procedures of imaging dat...
- The data are assumed to be obtained with the procedures...
- This document is based on the article below:
-- [[Ishiguro et al. 2011>http://www.nhao.jp/research/ann...
- In modifying and editing the article, some materials pr...
- You can use a set of the pipeline scripts working on th...
* The scheme of the data reduction [#cb6fd1da]
- The data reduction is outlined as follows. The names of...
+ Dark subtraction (''*.da.fits'')
+ Flatfielding (''*.fl.fits'')
+ Mask and interpolate the bad pixels
+ Mask and interpolate the hot pixels and dark pixels (''...
+ Generate the sky frame (''*.sk.fits'')
+ Subtract the sky frame (''*.ss.fits'')
+ Subtract the 'stripe' pattern of the detector (''*.sp.f...
+ Match the positions by shifting the individual frames
+ Coadd the frames to generate the combined image (''*.cm...
+ Register and assign the WCS to the combined frame (''*....
#ref(./ImageReduction_NIC.png,70%);
- The figure above shows the example image generated in e...
* 1. Dark subtraction [#l48d5654]
- Use the dark frames obtained by the procedure shown [[...
- Be sure to set the exposure time for the dark frames ex...
- Obtain 10-15 frames, and coadd them to generate the dar...
- The pipeline scripts installed in 'gamera' performs 3-s...
- If the cold shutter is not set to the appropriate posit...
- Subtract the coadded dark frame from the object frames ...
- The pipeline script generates the intermediate file nam...
After dark-subtraction j(date)_(frameID).(ObjectName)....
* 2. Flatfielding [#te07b759]
- This step corrects for the spatial inhomogeneity of the...
- Usually we recommend to use the twilight flat. [[This l...
- If you use the master flat frames provided by the obser...
- We do not have any specially-made software tools to gen...
- How to generate a flat frame is outlines as follows:
++ Obtain 5-10 (or more) pairs of flat frames with high- ...
++ Subtract the low-count frame from the high-count frame...
++ Homogenise the count levels by scale the individual fr...
++ Normalise the coadded frame so as to set the average c...
- Divide the dark-subtracted frame with the normalised fl...
- The pipeline script generates the intermediate file nam...
After flatfielding j(date)_(frameID).(ObjectName).fl.f...
* 3 & 4. Mask and interpolate the bad pixels and the hot/...
- Bad pixels (appear at fixed positions) can be removed b...
- The table shown below are the lists of bad pixels for J...
++ Mask the region with x1<x<x2, y1<y<y2, and interpolate...
++ If there are only two columns, mask only the single pi...
-- J band
277 291 134 148
186 191 229 236
260 270 1017 1023
-- H band
277 291 134 148
186 191 229 236
961 962 672 673
1002 1004 652 654
1005 1006 649 651
966 967 612 619
964 966 609 614
1001 1007 646 654
13 15 242 245
-- K band
140 141 549 551
162 163 806 807
162 805
163 804
164 167 801 803
162 170 795 800
171 173 798 802
186 191 229 236
277 291 134 148
320 321 586 589
321 323 591 593
778 779 682 688
780 786 671 676
779 780 677 680
785 789 670 671
- Hot/dark pixels can be removed using, e.g., IRAF/noao.i...
cosmicrays @obj_fl.lst @obj_cr1.lst
imarith @obj_cr1.lst * -1 @obj_cr2.lst
cosmicrays @obj_cr2.lst @obj_cr3.lst
imarith @obj_cr3 * -1 @obj_cr4.lst
obj_fl.lst: list of the flatfielded files
obj_cr?.lst: list of files to be generated
-- The recommended parameters for IRAF/cosmicrays are: th...
-- You can use other tools such as L.A.Cosmic
- The pipeline script generates the files named ''*.rr.fi...
After removing Bad/Hot/Dark pixel j(date)_(frameID).(...
* 5 & 6. Sky subtraction [#g19ae996]
- The 'sky' here means 'winding' pattern that cannot be c...
- Step 5. The sky frames are generated by median-stacking...
-- If the stars are not so crowded, you can use the raw o...
-- If there are many stars within the FoV, you need to ob...
-- The sky frame can be used even when containing several...
-- The procedures are outlined below. (This is not the on...
+++ Normalise each sky frame to the median pixel value.
+++ Median-stack the normalised frames. (e.g., using IRAF...
+++ Estimate the sky level of each object frame, and scal...
- Step 6. The sky subtraction is done by simply subtracti...
- The pipeline scripts generate the following two kinds o...
Sky frame generated j(ObjectName).sk.fits [e.g., jSN...
Sky-subtracted image j(date)_(frameID).(ObjectName).ss....
* 7. 'Stripe'-pattern subtraction [#ra32f91c]
- The NIC imaging data have 'stripe' pattern coming from ...
-- This pattern is thought to be due to the voltage fluct...
-- The amplitude of this pattern is almost constant for e...
-- There are two ways of subtraction as follows.
++ For sparse fields, i.e., fields containing few stars (...
--- Extract 20-100 lines without any stars, and average a...
--- Do the same procedure for both the upper- and lower h...
--- Subtract the 'stripe' pattern profile of the upper ha...
#ref(./NIC_colpattern.png);
--- In the example above the regions outlined with the gr...
++ For crowded fields, i.e., fields containing many stars...
--- The example below has many stars in the FoV, and 'lin...
--- Calculate the median count for each column for each o...
--- Subtract the profile from the object frames, similarl...
#ref(./NIC_colpattern_median.jpg,70%);
--- The example above shows the result of subtraction wit...
- The pipeline scripts generate the files named ''*.sp.fi...
After subtracting the 'stripe' pattern j(date)_(frameI...
- The pipeline scripts also try to register the WCS at th...
* 8 & 9. Position matching & stacking [#a730298d]
- Measure the positions of astrometric reference stars . ...
- Shift the images so that the reference stars are locate...
-- You do not need to take account of distortion, as the ...
-- The position angle is usually set to be constant, so t...
-- You can utilise the whole FoV of NIC by creating large...
- Stack the object frames after matching the positions (e...
- The pipeline scripts generates the files shown below, n...
After matching j(date)_(frameID).(ObjectName).sf.fits ...
After Stacking j(ObjectName).cm.fits [e.g., jSN2012dn...
* 10. Astrometry [#rc012d31]
- Obtain the coordinate system using the stars within the...
-- ccmap : Reads the list of object coordinates and corre...
-- ccsetwcs : Inputs the 'image to be registered the WCS'...
- This is not the only way to do this. You can also use [...
- See also: [[WCSTools>http://tdc-www.harvard.edu/wcstool...
- The pipeline script uses 'imwcs' of WCSTools, and regis...
gamera% ds9 &
gamera% getwcs.sh [file name].cm.fits
-- Note that the script does not run on machines other th...
- The script generates the following files named ''*.spw....
After 'stripe' subtraction + WCS j(date)_(frameID).(...
After stacking + WCS j(ObjectName).cmw.fits [e.g., j...
-- The astrometry process includes the calculation of the...
* Revision history [#pf25dc55]
- 2019.09.10 Created based on the Japanese version (T. Sa...
- 2019.09.12 Fully revised and opened for public (T. Saito)
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