Navodila za obdelavo slik
HR diagram kopice
(Restore this version)
Modified: 26 February 2016, 2:54 PM User: Bojan Dintinjana →
Posnamem 15 slik kopice M67 z filtrom V in še 15 slik z filtrom B. Čas osvetlitve je 60 in 120s. Snemalna datoteka s katero snemamo je takšna:
M67 08:51:18 +11:48:00 V 2 60 3
M67 08:51:18 +11:48:00 B 2 120 3
#.. in se ponovi 5 krat
Smiselno bi bilo še dodati nekaj posnetkov s krajšimi osvetlitvenimi časi, da bi lahko izmerili tudi svetlejše zvezde v zgornjem delu HR-diagama.
Vse slike si pozorno ogledamo in morebitne pokvarjene odstranimo. (premaknemo v podmapo bad). Slike najprej seštejem v linux konzoli:
$ cd ~/data/vdelu/V2015-02-18
$ sumimage.sh sM67V.fts M67_V_*.fts
$ sumimage.sh sM67B.fts M67_B_*.fts
pri tem uporabim že pripravljeno skripto sumimage.sh za seštevanje slik. Grem v terminal gterm in poženem iraf.
$ ecl
NOAO/IRAF PC-IRAF Revision 2.16.1 EXPORT Mon Oct 14 21:40:13 MST 2013
This is the EXPORT version of IRAF V2.16 supporting PC systems.
Welcome to IRAF. To list the available commands, type ? or ??. To get
detailed information about a command, type `help <command>'. To run a
command or load a package, type its name. Type `bye' to exit a
package, or `logout' to get out of the CL. Type `news' to find out
what is new in the version of the system you are using.
Visit http://iraf.net if you have questions or to report problems.
*** Checking update status... Your IRAF system is up to date
*** Using global login file: /home/vega/.iraf/login.cl
The following commands or packages are currently defined:
color. gemini. lists. optic. softools. utilities.
ctio. gmisc. mscred. phist. stecf. vo.
dataio. guiapps. mtools. plot. stsdas. wcstools.
dbms. images. noao. proto. system. xdimsum.
fitsutil. language. obsolete. rvsao. tables.
ecl> ecl> digiphot
apphot. daophot. photcal. ptools.
digiphot> apphot
aptest findpars@ pconvert polymark psort
center fitpsf pdump polypars@ qphot
centerpars@ fitsky pexamine polyphot radprof
daofind fitskypars@ phot prenumber wphot
datapars@ pcalc photpars@ pselect
apphot>
Naložim potrebne pakete za aperturno fotometrijo:
ecl> digiphot
apphot. daophot. photcal. ptools.
digiphot> apphot
aptest findpars@ pconvert polymark psort
center fitpsf pdump polypars@ qphot
centerpars@ fitsky pexamine polyphot radprof
daofind fitskypars@ phot prenumber wphot
datapars@ pcalc photpars@ pselect
apphot>
Seštete slike si ogledam in obrežem, vendar najprej preizkusim koordinate, tako da prikažem izrezano sliko:
apphot> !ds&
apphot> display sM67V.fts[21:1941,84:1950]
apphot> imcopy sM*.fts[21:1941,84:1950]
Z ukazom imcopy smo zdaj povozili originalne slike. Zdaj potrebujemo vrednost STDDEV in FWHM za obe sliki:
apphot> imstat sM67*.fts nclip=7
# IMAGE NPIX MEAN STDDEV MIN MAX
sM67B.fts 3463541 284.6 8.153 260.1 309.
sM67V.fts 3379345 741.1 7.582 718.4 763.9
Izmerim še fwhm z ukazom psfmeasure (glej navodila za fotometrijo), dobim:
JD IMAGE FWHM ELLI SKY STDEV RFLUX
2457072.4123843 sM67B.fts 6.39 0.15 285.2 8.6 1.000 50
2457072.4088715 sM67V.fts 6.53 0.17 739.4 8.2 1.802 50
Zdaj nastavim parametre za iskanje zvezd, najprej slika V:
PACKAGE = apphot
TASK = datapars
(scale = 1.) Image scale in units per pixel
(fwhmpsf= 6.39) FWHM of the PSF in scale units
(emissio= yes) Features are positive ?
(sigma = 8.15) Standard deviation of background in counts
(datamin= 100.) Minimum good data value
(datamax= 57000.) Maximum good data value
(noise = poisson) Noise model
(ccdread= RDNOISE) CCD readout noise image header keyword
(gain = GAIN) CCD gain image header keyword
(readnoi= 0.) CCD readout noise in electrons
(epadu = 1.) Gain in electrons per count
(exposur= EXPOSURE) Exposure time image header keyword
(airmass= AIRMASS) Airmass image header keyword
(filter = FILTER) Filter image header keyword
(obstime= JD) Time of observation image header keyword
(itime = 1.) Exposure time
(xairmas= INDEF) Airmass
(ifilter= INDEF) Filter
(otime = INDEF) Time of observation
(mode = ql)
($nargs = 0)
in še findpars:
PACKAGE = apphot
TASK = findpars
(thresho= 3.7) Threshold in sigma for feature detection
(nsigma = 1.5) Width of convolution kernel in sigma
(ratio = 1.) Ratio of minor to major axis of Gaussian kernel
(theta = 0.) Position angle of major axis of Gaussian kernel
(sharplo= 0.2) Lower bound on sharpness for feature detection
(sharphi= 1.) Upper bound on sharpness for feature detection
(roundlo= -1.) Lower bound on roundness for feature detection
(roundhi= 1.) Upper bound on roundness for feature detection
(mkdetec= no) Mark detected stars on the display ?
(mode = ql)
($nargs = 0)
Za prag detekcije izberem 3.7 sigma vrednost nad ozadjem, tako najde 750 zvezd, s kar sem zadovoljen. Nižja vrednost za prag najde več zvezd, vendar je tudi večja verjetnost, da detekcijo sproži šum na sliki. Smiselne so vrednosti nad recimo 3.0 sigma. Poiščem zvezde:
apphot> daofind sM67V.fts
FWHM of features in scale units (6.39) (CR or value):
New FWHM of features: 6.39 scale units 6.39 pixels
Standard deviation of background in counts (8.15) (CR or value):
New standard deviation of background: 8.15 counts
Detection threshold in sigma (3.7) (CR or value):
New detection threshold: 3.7 sigma 30.155 counts
Minimum good data value (100.) (CR or value):
New minimum good data value: 100. counts
Maximum good data value (57000.) (CR or value):
....
370.33 1853.97 -0.077 0.304 -0.273 -0.831 740
1066.71 1852.11 -0.323 0.320 -0.162 -0.265 741
1168.05 1853.52 -0.135 0.452 -0.233 -0.787 742
1296.45 1853.75 -0.088 0.693 -0.163 -0.988 743
1462.06 1853.60 -0.379 0.303 -0.226 -0.949 744
1744.33 1853.13 -0.072 0.571 -0.259 -0.733 745
1810.51 1853.77 -0.058 0.465 -0.217 -0.941 746
1880.10 1853.38 -0.038 0.941 -0.273 -0.768 747
1908.10 1854.02 -0.006 0.422 -0.244 -0.893 748
1653.85 1854.85 -0.111 0.224 -0.207 -0.457 749
1116.12 1855.17 -0.045 0.682 -0.485 -0.040 750
threshold: 30.155 relerr: 0.759 0.2 <= sharp <= 1. -1. <= round <= 1.
apphot>
Dobim datoteko s koordinatami zvezd sM67V.fts.coo.1. Takoj preverim, če je detekcija zvezd pravilna:
apphot> display sM67V.fts
frame to be written into (1:16) (1):
z1=692.9196 z2=789.7111
apphot> tvmark 1 sM67V.fts.coo.1 color=204
apphot>
In je vse v redu, najde skoraj vse zvezde, manjši izrez:
Zdaj zvezde še izmerim, aperturna fotometrija. Za vrednost zaslonke izberem 2.8 in nastavim s photpars:
PACKAGE = apphot
TASK = photpars
(weighti= constant) Photometric weighting scheme for wphot
(apertur= 2.8) List of aperture radii in scale units
(zmag = 25.) Zero point of magnitude scale
(mkapert= no) Draw apertures on the display
(mode = ql)
($nargs = 0)
in
apphot> phot sM67V.fts
Centering algorithm (centroid) (CR or value):
New centering algorithm: centroid
Centering box width in scale units (5.) (CR or value):
New centering box width: 5. scale units 5. pixels
Sky fitting algorithm (centroid) (CR or value):
Sky fitting algorithm: centroid
Inner radius of sky annulus in scale units (10.) (CR or value):
New inner radius of sky annulus: 10. scale units 10. pixels
Width of the sky annulus in scale units (10.) (CR or value):
New width of the sky annulus: 10. scale units 10. pixels
File/list of aperture radii in scale units (2.8) (CR or value):
Aperture radius 1: 2.8 scale units 2.8 pixels
Standard deviation of background in counts (8.15) (CR or value):
New standard deviation of background: 8.15 counts
Minimum good data value (100.) (CR or value):
New minimum good data value: 100. counts
Maximum good data value (57000.) (CR or value):
....
sM67V.fts 1168.38 1852.45 737.1207 25.253 err
sM67V.fts 1296.51 1853.95 735.4269 26.872 ok
sM67V.fts 1462.36 1852.69 731.5929 24.281 ok
sM67V.fts 1744.59 1852.14 736.6783 INDEF ok
sM67V.fts 1809.47 1853.65 735.891 INDEF err
sM67V.fts 1880.29 1853.00 733.3796 INDEF ok
sM67V.fts 1908.39 1852.94 732.4415 24.853 err
sM67V.fts 1653.87 1854.36 734.1455 24.573 ok
sM67V.fts 1116.50 1855.97 737.7919 INDEF ok
apphot>
In naredi datoteko sM67V.fts.mag.1 . Pri nekaterih zvezdah javi napako, v večini primerov gre za zvezdo ki je na robu slike ali pa ima vroč piksel. Te zvezde bomo izločili pri nadaljni obdelavi. Prav tako bomo iz datoteke mag vzeli smo podatke ki jih potrebujemo. Ti so koordinata x,y, magnituda in napaka:
apphot> pdump sM67V.fts.mag.1 > V.txt
Fields to be extracted (id,xc,yc,mag,merr):
Boolean expression (PERROR='NoError' & CERROR='NoError' & SERROR='NoError' & MAG!=INDEF & MSKY!=INDEF & MERR!=INDEF):
apphot>
Slabe zvezde, z napako, izloči parameter Boolean expression, za katerega navedemo logični izraz, ni napak in magnituda je izmerjena. Datoteka V.txt je naš delni rezultat. Enako ponovimo za sliko B in dobimo datoteko B.txt. Da lahko obe datoteki združimo, pretvorimo logične koordinate (piksli) x,y iz slike v ekvatorialni sistem, rektascenzija in deklinacija, le ti sta namreč invarjantni glede na slike torej za zvezdo vedno enaki:
apphot> epar wcsctran
PACKAGE = imcoords
TASK = wcsctran
input = V.txt The input coordinate files
output = V.wcs The output coordinate files
image = sM67V.fts The input images
inwcs = logical The input coordinate system
outwcs = world The output coordinate system
(columns= 2 3) List of input file columns
(units = native) List of input coordinate units
(formats= %12.8f) List of output coordinate formats
(min_sig= 11) Minimum precision of output coordinates
(verbose= yes) Write comments to the output file ?
(mode = ql)
apphot> wcsctran
Dobimo datoteko V.wcs v kateri so zdaj koordinate v ekvatorianem sistemu (world). Enako naredimo še za datoteko B.txt. Datoteki sestavim in naredim še barvno korekcijo. Programa sestavi.py in popraviBV.py sta v mapi za izmenjavo datotek.
$ ./sestavi.py V.wcs B.wcs > VB.wcs
$ ./popravekBV.py VB.wcs > VBstd.wcs
Končni rezultat dobim v datoteki VBstd.wcs, samo še narišem v gnuplotu:
gnuplot> set xlabel "B-V"
gnuplot> set ylabel "V"
gnuplot> plot [0:2][20:10] 'VBst.wcs' u 5:3 title ""
in dobim:
Za primerjavo graf iz članka :
