The file format used by GCX for star catalogs, recipies and observation reports consists of lists of token-value pairs. Each list is enclosed in brackets. The value part of each pair can be a number, a string (enclosed in double quotes) or another list. The order of the pairs within the list is not important.
A file can contain several top-level lists. Each such list is called a ``frame''. A typical recipe frame looks like:
( recipe ( object "aucyg" ra "20:18:32.76" dec "34:23:21.3"
equinox 2000 comments "generated from tycho2" )
sequence "tycho2"
stars (
(name "2680-1551" type std mag 7.48
ra "20:17:54.500" dec "34:05:25.22" perr 0.0071
comments "p=T "
smags "v=7.344/0.020 b=8.654/0.020 vt=7.483/0.011 bt=9.024/0.017"
flags ( astrom ) )
(name "2680-1588" type std mag 7.79
ra "20:16:56.755" dec "34:08:22.86" perr 0.0057
comments "p=T "
smags "v=7.795/0.020 b=7.745/0.020 vt=7.790/0.011 bt=7.731/0.015"
flags ( astrom ) )
(name "aucyg" type target mag 9.5
ra "20:18:32.76" dec "34:23:21.3"
comments "p=V t=M s=M6e-M7e m(p)=9.50/15.30"
flags ( var ) ) )
)
An observation report frame can look like:
( observation ( filter "b" object "aucyg" ra "20:18:39.31"
dec "34:23:05.6" equinox 2000 mjd 53236.9839856
telescope "SCT" aperture 30 exptime 20 sns_temp 238.3
latitude "44:25:50.0" longitude "-26:06:50.0"
altitude 75 airmass 1.223 observer "R. Corlan" )
noise ( read 7 eladu 2 flat 0 )
ap_par ( r1 5 r2 9 r3 13 sky_method "synthetic_mode" )
(name "AU_CYG_39" type std mag 12.1
ra "20:17:47.15" dec "34:32:01.4"
smags "v=12.062/-0.001 b-v=1.982/-0.002 b=14.044/0.002"
imags "b=-7.256/0.167"
residual -0.209 stderr 1.25
noise (photon 0.13 sky 0.074 read 0.075 scint 0.0021)
centroid (x 876.89 y 385.24 xerr 0.0085 yerr 0.0065 dx -0.18 dy -0.15)
flags ( astrom centered ) )
(name "AU_CYG_10" type std mag 13
ra "20:17:44.52" dec "34:21:00.0"
smags "v=12.961/-0.001 b-v=0.765/-0.001 b=13.726/0.001"
imags "b=-7.991/0.089"
residual 0.208 stderr 2.33
noise (photon 0.066 sky 0.038 read 0.038 scint 0.0021)
centroid (x 569.61 y 331.56 xerr 0.002 yerr 0.0017 dx 0.19 dy -0.17)
flags ( astrom centered ) )
(name "aucyg" type target mag 9.5
ra "20:18:32.76" dec "34:23:21.3"
comments "p=V t=M s=M6e-M7e m(p)=9.50/15.30"
smags "b=12.642/0.085"
imags "b=-8.867/0.042"
centroid (x 782.90 y 615.40 xerr 0.0079 yerr 0.0064 dx 0.17 dy 0.07)
noise (photon 0.031 sky 0.017 read 0.017 scint 0.0021)
flags ( var centered ) ) )
transform ( band "b" zp 21.509 zperr 0.074 zpme1 1.29 ) )
A typical catalog frame would be:
( catalog (comments "Internal catalog output")
stars (
( name "piuma" type catalog ra "08:39:11.70" dec "65:01:15.0"
flags ( var ) )
( name "lpup" type catalog ra "07:13:31.90" dec "-44:38:39.0"
flags ( var ) )
( name "piori" type catalog ra "04:54:15.10" dec "02:26:26.4"
flags ( var ) ) ) )
All three forms of the star file have in common the top-level token stars which is followed by the list of all stars within the frame. Each star is also represented by a list, having some of the following tokens:
| name | string | The name of the star; |
| type | symbol | The type of the star: std for standards, target for targets, catalog far catalog objects and field for field stars; |
| ra | string | Right ascension in HMS format; |
| dec | string | Declination in DMS format; |
| perr | number | Position error in arc seconds; |
| equinox | number | Equinox of coordinates; |
| mag | number | Generic magnitude of the star, used for display purposes only; |
| smags | string | A string describing the standard magnitudes of the star and their errors. See Section 7.7 for the format; |
| imags | string | A string describing the instrumental magnitudes of the star and their errors; |
| centroid | list | A list containing positional information. x and y are frame coordinates of the star's centroid. xerr amd yerr are the estimated position errors calculated by the centroiding code. dx and dy are the amounts by which the star's centroid is shifted from the catalog position; |
| noise | list | A list of components of the star's instrumental noise model; |
| residual | number | The residual of the star after the zeropoint fit; |
| stderr | number | The standard error (scaled residual) of the star after the zeropoint fit; |
| flags | list | A list of reduction flags. |
Some top-level tokens of the star files are:
| stars | list | List of stars in the frame; |
| recipe | list | A list of recipe parameters. Most important are the target object and field center coordinates; |
| observation | list | Parameters of the ccd frame from which the data was obtained. See Section 7.5 for more details; |
| catalog | list | Identifies the frame as a catalog frame. The most important token in this list is comments; |
| sequence | string | The source of the standard magnitudes in the star list; |
| noise | list | A list of parameters of the CCD noise model used to calculate instrumental errors; |
| ap_par | list | Parameters used by the aperture photometry routine (aperture sizes and sky estimation method); |
| transform | list | transformation coefficients, zeropoint and extinction coefficients used to calculate the standard magnitudes of target stars. |
The native star format can be converted to a tabular format using the report converter function as described in Appendix E.