AGO Teleskop

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 cgterm 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 najprej preizkusim koordinate:

apphot> !ds&
apphot> display sM67V.fts[21:1941,84:1950]
apphot> imcopy sM*.fts[21:1941,84:1950]

Z ukazom imcopy smo povozili originalne slike. Zdaj potrebujemo vrednost STDEV 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):

      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: