Astronomy 920 Commissioning of the Prime Focus Imaging Spectrograph

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Astronomy 920Commissioning of the Prime Focus
Imaging Spectrograph

• Meeting 7
• SALT IRAF Package
• Ken Nordsieck

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PFIS First Light Night

• NGC 1866 (LMC) 6290 Interference Filter 5 sec

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Quiz Question

• Why did we go to all that expense to get large
  diameter etalons?

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Scanning

• PFIS control system allows arbitrary sets of
  discrete steps (equal exposures)
• linear scan for line profiles
• dithering onto continuum for absorption lines
• Off axis, must take account of wavelength
  gradient due to cos ?
• center to edge gradient
• ?(r)/ ?0 1/ cos ? (1- .00365(r/4)2 )
  (24 Ang at Ha)
• Inside bullseye, wavelength changed by less
  than resolution
• D(bullseye) 1.4 (10,000/R)1/2
• - if object larger than bullseye, extend scan to
  cover same wavelengths
• - if object not round, pays to move telescope and
  rescan, instead of extending scan

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Accessing SALT IRAF package

• Source (environment variable salt)
• Unix /usr/local/salt
• MAC /usr/local/iraf/irafext/salt
• clgt salt loads salt task
• clgt help pfis lists pfis commands
• clgt pfis loads pfis subtask
• clgt cd working directory/yyyymmdd

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PFIS commands
PFIS/ SALT IRAF Package Hierarchy implemented
lower level pprepare p pired
uce r pmosaic m imcoadd pgain pbias ps
reduce ps pstransform t psskysub s psextract e
scombine piflat psflat pswavelength psca
librate c psstandard pbpm pscut

• Raw data
• name Pyyyyddddssss.fits, ie P200510200079.fits
• "multiextension" fits file, one for each of 6
  amplifiers open in DS9 with "open other/ open
  mosaic IRAF"
• Each stage of processing prepends a letter or two
• Imaging (pireduce, pmosaic) mrpP200510200097.fits
  
• Spectroscopy (psreduce) psP2.....

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Imaging

• pprepare (p)
• check header validity,
• get data from calibration database
• pireduce (r)
• remove crosstalk
• subtract mean of overscan in each amp, trim
• divide by gain for each amp
• subtract bias, if specified
• subtract dark, if specified
• divide by flat, if specified
• pbias run pireduce on bias frames, bias/ dark/
  flat turned off
• pflat (TBI) run pireduce on flat frames, dark/
  flat turned off
• pmosaic (m)
• combine amplifiers and ccd's into single fits
  files
• can now be opened as normal image by DS9
• imcoadd (TBI)
• remove distortion
• combine mosaiced images, registering and removing
  cosmic rays

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Spectroscopy

• psreduce (ps)
• run pireduce
• run pmosaic
• using slitmask definition file (MDF), cut into
  one piece for each slit (pscut)
• apply first guess wavelength calibration to each
• psflat (TBI) run psreduce on spectral flats
  (tungsten continuum spectrum)
• pswavelength identify lines and update wavelength
  dispersion calibration for wavecal frame
• pstransform (TBI) resample cut spectra onto
  linear wavelength vs space grid
• psskysub, psextract (TBI) extract to 1-d raw
  spectra
• pscalibrate compute flux cal from flux standard

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Configuration Data

• Instrument configuration data salt/pfis/data
  (IRAF pfisdata)
• PFISamps gain and noise for ccd amps
• PFISxtalk crosstalk coefficients
• PFISgeom orientation of CCD's in mosaic
• PFISdistortion correct pincushion distortion of
  collimator (r R AR3 BR5)
• PFISfilters. filter list with pointers to
  transmission curves in /filters
• PFISgratings. grating list with alignment
  calibration
• /masks. mask definition files
• /linelists. linelists for calibration lamps Xe,
  Ne, HgAr