AGO Teleskop

Primer 1:

Imamo 8 slik asteroida  (297) Caecilia posnetih z filtrom V in bomo izmeril njegov sij. Slike so:

bojan@lib:~/data/vdelu/Caecilia$ ll -rt
total 82136
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_222.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_224.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_223.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_225.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_227.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_226.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_229.fts
-rw-rw-r--  1 bojan bojan 8406720 Dec  9 15:36 Caecilia_V_228.fts

ecl> noao
      airvac        astutil.      ll            observatory   surfphot.
      artdata.      digiphot.     mtlocal.      obsutil.      twodspec.
      astcat.       focas.        nobsolete.    onedspec.     
      astrometry.   imred.        nproto.       rv.           

noao> 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       

Sledi nastavitev parametrov, najprej izračunam vrednost sigma neba, izmerim več slik, recimo sliko na začetku, na sredini in na koncu opazovaja:

apphot>  imstat Caecilia_V_22*.fts nclip=5
#               IMAGE      NPIX      MEAN    STDDEV       MIN       MAX
   Caecilia_V_222.fts   4173484     539.5     26.05      462.      617.
   Caecilia_V_225.fts   4172849      549.     26.17      471.      627.
   Caecilia_V_227.fts   4172156      547.     26.18      469.      625.

apphot> datapars
PACKAGE = apphot
   TASK = datapars

(scale  =                   1.) Image scale in units per pixel
(fwhmpsf=                  2.5) FWHM of the PSF in scale units
(emissio=                  yes) Features are positive ?
(sigma  =                  26.) 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)

Urejanje parametrov končam z tipko ctrl-D. Naslednja klučna nastavitev je velikost aperture. Če izbere premajhno, izgubim del svetlobe, če pa izberem preveliko potem zajamem v meritev še velik del neba, ki prinese tudi veliko šuma. Običajno izberemo za velikost nekoliko manjšo vrednost od FWHM.  Izmerim še

apphot> obsutil
      bitcount    cgiparse    kpno.       psfmeasure  specfocus   sptime
      ccdtime     findgain    pairmass    shutcor     specpars@   starfocus

 psfmeasure Caecilia_V_222.fts
** Select stars to measure with 'm' and finish with 'q'.
** Additional options are '?', 'g', and :show.
qNOAO/IRAF V2.16.1 bojan@lib Thu 13:27:21 21-Jan-2016

          Image  Column    Line     Mag    FWHM   Ellip      PA SAT
Caecilia_V_222.  948.44 1036.26    0.07   3.258    0.11     -26
                1038.39 1058.44    1.52   3.320    0.17     -20
                 957.44  948.46    0.00   3.080    0.16     -28
                1176.95  909.18    1.78   3.322    0.13     -26
                1179.85  875.30    0.68   3.116    0.18     -37
                 722.36  811.29    2.53   3.070    0.11      10
                 695.00  794.91    1.71   2.898    0.23     -21
                 888.08  788.07    1.80   2.852    0.28     -33
                 888.08  788.07    1.80   2.852    0.28     -33

  Average full width at half maximum (FWHM) of 3.1265

Zdaj nastavim še aperturo in sicer na vrednost 2.8

apphot> 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)

Na sliki si s pomočjo programa ds9 izberem primerjalne zvezde