## Parameters

### Reference Catalogue:

`-C,--cal`
  The calibration is specified by an exterior entity. The values are saved to a PHOTOMETRY extension header and counts are converted to photons for both image and table values.
`-c,--cat`
  Reference photometric catalogue. A fits table with coordinates and magnitudes of reference stars. One can be a selection from a "real" catalogue or a table prepared by oneself. See section Preparation of Photometric Catalogue, how create this table by hand.
`-r,--ref`
  Reference frame is used. The reference frame usually created by `-c,-C` options. Useful for relative photometry.
`-f,--filters`
  Filters used for calibration.
`-F,--filter-ref`
  Reference filter for calibration.
`--col-ra`
  Right Ascension column. Default is RAJ2000.
`--col-dec`
  Declination column. Default is DEJ2000.
`--col-mag`
  Magnitude column(s). Default is the filter (-f option) with 'mag' suffix like `-f V --col-mag Vmag` (?).
`--col-magerr`
  Magnitude std. error column(s) (no default). If this parameter is omited, errors are estimated as the square of photons derived from magnitudes.
`--tol`
  search radius for object identification in degrees (default 5*FWHM)

### Calibration specific:

`--photsys-ref`
  reference (standard) photometric system (catalogue)
`--photsys-instr`
  instrumental photometric system (frames)
`-q, --quantity`
  calibrated quantities by default: PHRATE, FLUX, FNU, FLAM, MAG, ABMAG, STMAG (see description), multiple quantities can be used, separated by colon

### Photometric system:

`--tratab`
  Table describing conversion from instrumental to reference photo-system. Usually product of phfotran.
`--phsystab`
  A table with photometric system definitions (specification)
`--list`
  Lists available photometric systems. Their identifiers are names of extensions in (photometric system definitions) file.

### Common:

`-th, --threshold`
  Select stars on both reference and calibrated frames (not applied on catalogues) with its stellar flux to a sky noise (signal to noise) ratio greater then the threshold value. Both the values are determined in the same aperture. The proper choice is crucial for photometry precision because it helps to select only bright stars with minimal pollution by the sky noise. The default value 5 is very conservative setup. It is suitable for bad conditions (like urban or a full moon light observations). Standard and good conditions will allow lower ratios. In an ideal case, it can be under one for best results.
`-e, --maxerr`
  Select stars on both reference and calibrated frame (not applied on catalogues) with its relative flux error smaller than the error limit. The value does not limits the final precision, but limits fluency of noisy data. The default value 0.1 (ten percents, about tenth of magnitude) will also include relative imprecise stars into both calibration and calibrated set. The values under 0.01 and lower will select only precise and suitable calibration stars.
`--area`
  Area of telescope aperture in square meters [m2].
`--saper`
  selects appropriate aperture from PHOTOMETRY extension. By default, flux in infinite aperture is used.
`--apcorr`
  sets the aperture correction. This correction converts fluxes in an aperture to the total flux (infinite aperture). The value of correction should be obtained by gphot.
`--advanced`
  Advanced format. Additional extensions (results of star find, photometry and residuals) are included. This format is not used by default because result FITS is twice or more bigger.

See Common options for input/output filenames.

When options for the area and the reference and instrumental systems are used, FITS header is updated according to provided values.

Default values for coordinates will be usually unsatisfactory.